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freebsd-dev/lib/libthr/thread/thr_join.c

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- Add libthr but don't hook it up to the regular build yet. This is an adaptation of libc_r for the thr system call interface. This is beta quality code.
2003-04-01 03:46:29 +00:00
/*
* Copyright (c) 1995 John Birrell <jb@cimlogic.com.au>.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by John Birrell.
* 4. Neither the name of the author nor the names of any co-contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $FreeBSD$
*/
#include <errno.h>
#include <pthread.h>
Sweep through pthread locking and use the new locking primitives for libthr.
2003-06-29 23:51:04 +00:00
#include <stdlib.h>
- Add libthr but don't hook it up to the regular build yet. This is an adaptation of libc_r for the thr system call interface. This is beta quality code.
2003-04-01 03:46:29 +00:00
#include "thr_private.h"
__weak_reference(_pthread_join, pthread_join);
int
_pthread_join(pthread_t pthread, void **thread_return)
{
1. Now that it's a thread's state is changed from within the kernel, where no userland locks are heald, the dead thread lock can no longer protect access to it. Therefore, instead of using an if (!dead)...else clause after walking the active threads list test the thread pointer before deciding not to walk the dead threads list. If the thread pointer is null it means it was not found in the active threads list and the dead threads list should be checked. 2. Do not free the stack of a thread that is not marked dead. This is the 2nd and final part of eliminating the race to free a thread's stack. MFC after: 3 days
2004-10-13 11:42:20 +00:00
int ret, dead;
- Add libthr but don't hook it up to the regular build yet. This is an adaptation of libc_r for the thr system call interface. This is beta quality code.
2003-04-01 03:46:29 +00:00
pthread_t thread;
/* Check if the caller has specified an invalid thread: */
Make libthr async-signal-safe without costly signal masking. The guidlines I followed are: Only 3 functions (pthread_cancel, pthread_setcancelstate, pthread_setcanceltype) are required to be async-signal-safe by POSIX. None of the rest of the pthread api is required to be async-signal-safe. This means that only the three mentioned functions are safe to use from inside signal handlers. However, there are certain system/libc calls that are cancellation points that a caller may call from within a signal handler, and since they are cancellation points calls have to be made into libthr to test for cancellation and exit the thread if necessary. So, the cancellation test and thread exit code paths must be async-signal-safe as well. A summary of the changes follows: o Almost all of the code paths that masked signals, as well as locking the pthread structure now lock only the pthread structure. o Signals are masked (and left that way) as soon as a thread enters pthread_exit(). o The active and dead threads locks now explicitly require that signals are masked. o Access to the isdead field of the pthread structure is protected by both the active and dead list locks for writing. Either one is sufficient for reading. o The thread state and type fields have been combined into one three-state switch to make it easier to read without requiring a lock. It doesn't need a lock for writing (and therefore for reading either) because only the current thread can write to it and it is an integer value. o The thread state field of the pthread structure has been eliminated. It was an unnecessary field that mostly duplicated the flags field, but required additional locking that would make a lot more code paths require signal masking. Any truly unique values (such as PS_DEAD) have been reborn as separate members of the pthread structure. o Since the mutex and condvar pthread functions are not async-signal-safe there is no need to muck about with the wait queues when handling a signal ... o ... which also removes the need for wrapping signal handlers and sigaction(2). o The condvar and mutex async-cancellation code had to be revised as a result of some of these changes, which resulted in semi-unrelated changes which would have been difficult to work on as a separate commit, so they are included as well. The only part of the changes I am worried about is related to locking for the pthread joining fields. But, I will take a closer look at them once this mega-patch is committed.
2004-05-20 12:06:16 +00:00
if (pthread->magic != PTHREAD_MAGIC)
- Add libthr but don't hook it up to the regular build yet. This is an adaptation of libc_r for the thr system call interface. This is beta quality code.
2003-04-01 03:46:29 +00:00
/* Invalid thread: */
return(EINVAL);
/* Check if the caller has specified itself: */
Make libthr async-signal-safe without costly signal masking. The guidlines I followed are: Only 3 functions (pthread_cancel, pthread_setcancelstate, pthread_setcanceltype) are required to be async-signal-safe by POSIX. None of the rest of the pthread api is required to be async-signal-safe. This means that only the three mentioned functions are safe to use from inside signal handlers. However, there are certain system/libc calls that are cancellation points that a caller may call from within a signal handler, and since they are cancellation points calls have to be made into libthr to test for cancellation and exit the thread if necessary. So, the cancellation test and thread exit code paths must be async-signal-safe as well. A summary of the changes follows: o Almost all of the code paths that masked signals, as well as locking the pthread structure now lock only the pthread structure. o Signals are masked (and left that way) as soon as a thread enters pthread_exit(). o The active and dead threads locks now explicitly require that signals are masked. o Access to the isdead field of the pthread structure is protected by both the active and dead list locks for writing. Either one is sufficient for reading. o The thread state and type fields have been combined into one three-state switch to make it easier to read without requiring a lock. It doesn't need a lock for writing (and therefore for reading either) because only the current thread can write to it and it is an integer value. o The thread state field of the pthread structure has been eliminated. It was an unnecessary field that mostly duplicated the flags field, but required additional locking that would make a lot more code paths require signal masking. Any truly unique values (such as PS_DEAD) have been reborn as separate members of the pthread structure. o Since the mutex and condvar pthread functions are not async-signal-safe there is no need to muck about with the wait queues when handling a signal ... o ... which also removes the need for wrapping signal handlers and sigaction(2). o The condvar and mutex async-cancellation code had to be revised as a result of some of these changes, which resulted in semi-unrelated changes which would have been difficult to work on as a separate commit, so they are included as well. The only part of the changes I am worried about is related to locking for the pthread joining fields. But, I will take a closer look at them once this mega-patch is committed.
2004-05-20 12:06:16 +00:00
if (pthread == curthread)
- Add libthr but don't hook it up to the regular build yet. This is an adaptation of libc_r for the thr system call interface. This is beta quality code.
2003-04-01 03:46:29 +00:00
/* Avoid a deadlock condition: */
return(EDEADLK);
/*
* Search for the specified thread in the list of active threads. This
* is done manually here rather than calling _find_thread() because
* the searches in _thread_list and _dead_list (as well as setting up
* join/detach state) have to be done atomically.
*/
1. Now that it's a thread's state is changed from within the kernel, where no userland locks are heald, the dead thread lock can no longer protect access to it. Therefore, instead of using an if (!dead)...else clause after walking the active threads list test the thread pointer before deciding not to walk the dead threads list. If the thread pointer is null it means it was not found in the active threads list and the dead threads list should be checked. 2. Do not free the stack of a thread that is not marked dead. This is the 2nd and final part of eliminating the race to free a thread's stack. MFC after: 3 days
2004-10-13 11:42:20 +00:00
ret = 0;
dead = 0;
thread = NULL;
Make libthr async-signal-safe without costly signal masking. The guidlines I followed are: Only 3 functions (pthread_cancel, pthread_setcancelstate, pthread_setcanceltype) are required to be async-signal-safe by POSIX. None of the rest of the pthread api is required to be async-signal-safe. This means that only the three mentioned functions are safe to use from inside signal handlers. However, there are certain system/libc calls that are cancellation points that a caller may call from within a signal handler, and since they are cancellation points calls have to be made into libthr to test for cancellation and exit the thread if necessary. So, the cancellation test and thread exit code paths must be async-signal-safe as well. A summary of the changes follows: o Almost all of the code paths that masked signals, as well as locking the pthread structure now lock only the pthread structure. o Signals are masked (and left that way) as soon as a thread enters pthread_exit(). o The active and dead threads locks now explicitly require that signals are masked. o Access to the isdead field of the pthread structure is protected by both the active and dead list locks for writing. Either one is sufficient for reading. o The thread state and type fields have been combined into one three-state switch to make it easier to read without requiring a lock. It doesn't need a lock for writing (and therefore for reading either) because only the current thread can write to it and it is an integer value. o The thread state field of the pthread structure has been eliminated. It was an unnecessary field that mostly duplicated the flags field, but required additional locking that would make a lot more code paths require signal masking. Any truly unique values (such as PS_DEAD) have been reborn as separate members of the pthread structure. o Since the mutex and condvar pthread functions are not async-signal-safe there is no need to muck about with the wait queues when handling a signal ... o ... which also removes the need for wrapping signal handlers and sigaction(2). o The condvar and mutex async-cancellation code had to be revised as a result of some of these changes, which resulted in semi-unrelated changes which would have been difficult to work on as a separate commit, so they are included as well. The only part of the changes I am worried about is related to locking for the pthread joining fields. But, I will take a closer look at them once this mega-patch is committed.
2004-05-20 12:06:16 +00:00
_thread_sigblock();
Start locking up the active and dead threads lists. The active threads list is protected by a spinlock_t, but the dead list uses a pthread_mutex because it is necessary to synchronize other threads with the garbage collector thread. Lock/Unlock macros are used so it's easier to make changes to the locks in the future. The 'dead thread list' lock is intended to replace the gc mutex. This doesn't have any practical ramifications. It simply makes it clearer what the purpose of the lock is. The gc will use this lock, instead of the gc mutex, to synchronize access to the dead list with other threads. Modify _pthread_exit() to use these two new locks instead of GIANT_LOCK, and also to properly lock and protect thread state changes, especially with respect to a joining thread. The gc thread was also re-arranged to be more organized and less nested. _pthread_join() was also modified to use the thread list locks. However, locking and unlocking here needs special care because a thread could find itself in a position where it's joining an exiting thread that is waiting on the dead list lock, which this thread (joiner) holds. If the joiner doesn't take care to lock *and* unlock in the same order they (the joiner and the joinee) could deadlock against each other. Approved by: re/blanket libthr
2003-05-25 08:31:33 +00:00
DEAD_LIST_LOCK;
THREAD_LIST_LOCK;
Make libthr async-signal-safe without costly signal masking. The guidlines I followed are: Only 3 functions (pthread_cancel, pthread_setcancelstate, pthread_setcanceltype) are required to be async-signal-safe by POSIX. None of the rest of the pthread api is required to be async-signal-safe. This means that only the three mentioned functions are safe to use from inside signal handlers. However, there are certain system/libc calls that are cancellation points that a caller may call from within a signal handler, and since they are cancellation points calls have to be made into libthr to test for cancellation and exit the thread if necessary. So, the cancellation test and thread exit code paths must be async-signal-safe as well. A summary of the changes follows: o Almost all of the code paths that masked signals, as well as locking the pthread structure now lock only the pthread structure. o Signals are masked (and left that way) as soon as a thread enters pthread_exit(). o The active and dead threads locks now explicitly require that signals are masked. o Access to the isdead field of the pthread structure is protected by both the active and dead list locks for writing. Either one is sufficient for reading. o The thread state and type fields have been combined into one three-state switch to make it easier to read without requiring a lock. It doesn't need a lock for writing (and therefore for reading either) because only the current thread can write to it and it is an integer value. o The thread state field of the pthread structure has been eliminated. It was an unnecessary field that mostly duplicated the flags field, but required additional locking that would make a lot more code paths require signal masking. Any truly unique values (such as PS_DEAD) have been reborn as separate members of the pthread structure. o Since the mutex and condvar pthread functions are not async-signal-safe there is no need to muck about with the wait queues when handling a signal ... o ... which also removes the need for wrapping signal handlers and sigaction(2). o The condvar and mutex async-cancellation code had to be revised as a result of some of these changes, which resulted in semi-unrelated changes which would have been difficult to work on as a separate commit, so they are included as well. The only part of the changes I am worried about is related to locking for the pthread joining fields. But, I will take a closer look at them once this mega-patch is committed.
2004-05-20 12:06:16 +00:00
if (!pthread->isdead) {
TAILQ_FOREACH(thread, &_thread_list, tle) {
if (thread == pthread) {
PTHREAD_LOCK(pthread);
break;
}
Start locking up the active and dead threads lists. The active threads list is protected by a spinlock_t, but the dead list uses a pthread_mutex because it is necessary to synchronize other threads with the garbage collector thread. Lock/Unlock macros are used so it's easier to make changes to the locks in the future. The 'dead thread list' lock is intended to replace the gc mutex. This doesn't have any practical ramifications. It simply makes it clearer what the purpose of the lock is. The gc will use this lock, instead of the gc mutex, to synchronize access to the dead list with other threads. Modify _pthread_exit() to use these two new locks instead of GIANT_LOCK, and also to properly lock and protect thread state changes, especially with respect to a joining thread. The gc thread was also re-arranged to be more organized and less nested. _pthread_join() was also modified to use the thread list locks. However, locking and unlocking here needs special care because a thread could find itself in a position where it's joining an exiting thread that is waiting on the dead list lock, which this thread (joiner) holds. If the joiner doesn't take care to lock *and* unlock in the same order they (the joiner and the joinee) could deadlock against each other. Approved by: re/blanket libthr
2003-05-25 08:31:33 +00:00
}
1. Now that it's a thread's state is changed from within the kernel, where no userland locks are heald, the dead thread lock can no longer protect access to it. Therefore, instead of using an if (!dead)...else clause after walking the active threads list test the thread pointer before deciding not to walk the dead threads list. If the thread pointer is null it means it was not found in the active threads list and the dead threads list should be checked. 2. Do not free the stack of a thread that is not marked dead. This is the 2nd and final part of eliminating the race to free a thread's stack. MFC after: 3 days
2004-10-13 11:42:20 +00:00
}
if (thread == NULL) {
Make libthr async-signal-safe without costly signal masking. The guidlines I followed are: Only 3 functions (pthread_cancel, pthread_setcancelstate, pthread_setcanceltype) are required to be async-signal-safe by POSIX. None of the rest of the pthread api is required to be async-signal-safe. This means that only the three mentioned functions are safe to use from inside signal handlers. However, there are certain system/libc calls that are cancellation points that a caller may call from within a signal handler, and since they are cancellation points calls have to be made into libthr to test for cancellation and exit the thread if necessary. So, the cancellation test and thread exit code paths must be async-signal-safe as well. A summary of the changes follows: o Almost all of the code paths that masked signals, as well as locking the pthread structure now lock only the pthread structure. o Signals are masked (and left that way) as soon as a thread enters pthread_exit(). o The active and dead threads locks now explicitly require that signals are masked. o Access to the isdead field of the pthread structure is protected by both the active and dead list locks for writing. Either one is sufficient for reading. o The thread state and type fields have been combined into one three-state switch to make it easier to read without requiring a lock. It doesn't need a lock for writing (and therefore for reading either) because only the current thread can write to it and it is an integer value. o The thread state field of the pthread structure has been eliminated. It was an unnecessary field that mostly duplicated the flags field, but required additional locking that would make a lot more code paths require signal masking. Any truly unique values (such as PS_DEAD) have been reborn as separate members of the pthread structure. o Since the mutex and condvar pthread functions are not async-signal-safe there is no need to muck about with the wait queues when handling a signal ... o ... which also removes the need for wrapping signal handlers and sigaction(2). o The condvar and mutex async-cancellation code had to be revised as a result of some of these changes, which resulted in semi-unrelated changes which would have been difficult to work on as a separate commit, so they are included as well. The only part of the changes I am worried about is related to locking for the pthread joining fields. But, I will take a closer look at them once this mega-patch is committed.
2004-05-20 12:06:16 +00:00
TAILQ_FOREACH(thread, &_dead_list, dle) {
Start locking up the active and dead threads lists. The active threads list is protected by a spinlock_t, but the dead list uses a pthread_mutex because it is necessary to synchronize other threads with the garbage collector thread. Lock/Unlock macros are used so it's easier to make changes to the locks in the future. The 'dead thread list' lock is intended to replace the gc mutex. This doesn't have any practical ramifications. It simply makes it clearer what the purpose of the lock is. The gc will use this lock, instead of the gc mutex, to synchronize access to the dead list with other threads. Modify _pthread_exit() to use these two new locks instead of GIANT_LOCK, and also to properly lock and protect thread state changes, especially with respect to a joining thread. The gc thread was also re-arranged to be more organized and less nested. _pthread_join() was also modified to use the thread list locks. However, locking and unlocking here needs special care because a thread could find itself in a position where it's joining an exiting thread that is waiting on the dead list lock, which this thread (joiner) holds. If the joiner doesn't take care to lock *and* unlock in the same order they (the joiner and the joinee) could deadlock against each other. Approved by: re/blanket libthr
2003-05-25 08:31:33 +00:00
if (thread == pthread) {
Make libthr async-signal-safe without costly signal masking. The guidlines I followed are: Only 3 functions (pthread_cancel, pthread_setcancelstate, pthread_setcanceltype) are required to be async-signal-safe by POSIX. None of the rest of the pthread api is required to be async-signal-safe. This means that only the three mentioned functions are safe to use from inside signal handlers. However, there are certain system/libc calls that are cancellation points that a caller may call from within a signal handler, and since they are cancellation points calls have to be made into libthr to test for cancellation and exit the thread if necessary. So, the cancellation test and thread exit code paths must be async-signal-safe as well. A summary of the changes follows: o Almost all of the code paths that masked signals, as well as locking the pthread structure now lock only the pthread structure. o Signals are masked (and left that way) as soon as a thread enters pthread_exit(). o The active and dead threads locks now explicitly require that signals are masked. o Access to the isdead field of the pthread structure is protected by both the active and dead list locks for writing. Either one is sufficient for reading. o The thread state and type fields have been combined into one three-state switch to make it easier to read without requiring a lock. It doesn't need a lock for writing (and therefore for reading either) because only the current thread can write to it and it is an integer value. o The thread state field of the pthread structure has been eliminated. It was an unnecessary field that mostly duplicated the flags field, but required additional locking that would make a lot more code paths require signal masking. Any truly unique values (such as PS_DEAD) have been reborn as separate members of the pthread structure. o Since the mutex and condvar pthread functions are not async-signal-safe there is no need to muck about with the wait queues when handling a signal ... o ... which also removes the need for wrapping signal handlers and sigaction(2). o The condvar and mutex async-cancellation code had to be revised as a result of some of these changes, which resulted in semi-unrelated changes which would have been difficult to work on as a separate commit, so they are included as well. The only part of the changes I am worried about is related to locking for the pthread joining fields. But, I will take a closer look at them once this mega-patch is committed.
2004-05-20 12:06:16 +00:00
PTHREAD_LOCK(pthread);
1. Now that it's a thread's state is changed from within the kernel, where no userland locks are heald, the dead thread lock can no longer protect access to it. Therefore, instead of using an if (!dead)...else clause after walking the active threads list test the thread pointer before deciding not to walk the dead threads list. If the thread pointer is null it means it was not found in the active threads list and the dead threads list should be checked. 2. Do not free the stack of a thread that is not marked dead. This is the 2nd and final part of eliminating the race to free a thread's stack. MFC after: 3 days
2004-10-13 11:42:20 +00:00
dead = 1;
- Add libthr but don't hook it up to the regular build yet. This is an adaptation of libc_r for the thr system call interface. This is beta quality code.
2003-04-01 03:46:29 +00:00
break;
Start locking up the active and dead threads lists. The active threads list is protected by a spinlock_t, but the dead list uses a pthread_mutex because it is necessary to synchronize other threads with the garbage collector thread. Lock/Unlock macros are used so it's easier to make changes to the locks in the future. The 'dead thread list' lock is intended to replace the gc mutex. This doesn't have any practical ramifications. It simply makes it clearer what the purpose of the lock is. The gc will use this lock, instead of the gc mutex, to synchronize access to the dead list with other threads. Modify _pthread_exit() to use these two new locks instead of GIANT_LOCK, and also to properly lock and protect thread state changes, especially with respect to a joining thread. The gc thread was also re-arranged to be more organized and less nested. _pthread_join() was also modified to use the thread list locks. However, locking and unlocking here needs special care because a thread could find itself in a position where it's joining an exiting thread that is waiting on the dead list lock, which this thread (joiner) holds. If the joiner doesn't take care to lock *and* unlock in the same order they (the joiner and the joinee) could deadlock against each other. Approved by: re/blanket libthr
2003-05-25 08:31:33 +00:00
}
Make libthr async-signal-safe without costly signal masking. The guidlines I followed are: Only 3 functions (pthread_cancel, pthread_setcancelstate, pthread_setcanceltype) are required to be async-signal-safe by POSIX. None of the rest of the pthread api is required to be async-signal-safe. This means that only the three mentioned functions are safe to use from inside signal handlers. However, there are certain system/libc calls that are cancellation points that a caller may call from within a signal handler, and since they are cancellation points calls have to be made into libthr to test for cancellation and exit the thread if necessary. So, the cancellation test and thread exit code paths must be async-signal-safe as well. A summary of the changes follows: o Almost all of the code paths that masked signals, as well as locking the pthread structure now lock only the pthread structure. o Signals are masked (and left that way) as soon as a thread enters pthread_exit(). o The active and dead threads locks now explicitly require that signals are masked. o Access to the isdead field of the pthread structure is protected by both the active and dead list locks for writing. Either one is sufficient for reading. o The thread state and type fields have been combined into one three-state switch to make it easier to read without requiring a lock. It doesn't need a lock for writing (and therefore for reading either) because only the current thread can write to it and it is an integer value. o The thread state field of the pthread structure has been eliminated. It was an unnecessary field that mostly duplicated the flags field, but required additional locking that would make a lot more code paths require signal masking. Any truly unique values (such as PS_DEAD) have been reborn as separate members of the pthread structure. o Since the mutex and condvar pthread functions are not async-signal-safe there is no need to muck about with the wait queues when handling a signal ... o ... which also removes the need for wrapping signal handlers and sigaction(2). o The condvar and mutex async-cancellation code had to be revised as a result of some of these changes, which resulted in semi-unrelated changes which would have been difficult to work on as a separate commit, so they are included as well. The only part of the changes I am worried about is related to locking for the pthread joining fields. But, I will take a closer look at them once this mega-patch is committed.
2004-05-20 12:06:16 +00:00
}
}
- Add libthr but don't hook it up to the regular build yet. This is an adaptation of libc_r for the thr system call interface. This is beta quality code.
2003-04-01 03:46:29 +00:00
/* Check if the thread was not found or has been detached: */
o Don't explicitly check the thread for NULL. That is the caller's responsibility. o If a thread is not joinable, the correct return value is EINVAL.
2004-03-29 13:53:43 +00:00
if (thread == NULL) {
Revise the unlock order in _pthread_join(). Also, if the joined thread is not dead, the join loop is guaranteed to execute at least once, so there is no need to pick up the thread list lock after we return from suspenstion only to release it after the loop. Approved by: re/blanket libthr
2003-05-26 00:28:49 +00:00
THREAD_LIST_UNLOCK;
Start locking up the active and dead threads lists. The active threads list is protected by a spinlock_t, but the dead list uses a pthread_mutex because it is necessary to synchronize other threads with the garbage collector thread. Lock/Unlock macros are used so it's easier to make changes to the locks in the future. The 'dead thread list' lock is intended to replace the gc mutex. This doesn't have any practical ramifications. It simply makes it clearer what the purpose of the lock is. The gc will use this lock, instead of the gc mutex, to synchronize access to the dead list with other threads. Modify _pthread_exit() to use these two new locks instead of GIANT_LOCK, and also to properly lock and protect thread state changes, especially with respect to a joining thread. The gc thread was also re-arranged to be more organized and less nested. _pthread_join() was also modified to use the thread list locks. However, locking and unlocking here needs special care because a thread could find itself in a position where it's joining an exiting thread that is waiting on the dead list lock, which this thread (joiner) holds. If the joiner doesn't take care to lock *and* unlock in the same order they (the joiner and the joinee) could deadlock against each other. Approved by: re/blanket libthr
2003-05-25 08:31:33 +00:00
DEAD_LIST_UNLOCK;
Make libthr async-signal-safe without costly signal masking. The guidlines I followed are: Only 3 functions (pthread_cancel, pthread_setcancelstate, pthread_setcanceltype) are required to be async-signal-safe by POSIX. None of the rest of the pthread api is required to be async-signal-safe. This means that only the three mentioned functions are safe to use from inside signal handlers. However, there are certain system/libc calls that are cancellation points that a caller may call from within a signal handler, and since they are cancellation points calls have to be made into libthr to test for cancellation and exit the thread if necessary. So, the cancellation test and thread exit code paths must be async-signal-safe as well. A summary of the changes follows: o Almost all of the code paths that masked signals, as well as locking the pthread structure now lock only the pthread structure. o Signals are masked (and left that way) as soon as a thread enters pthread_exit(). o The active and dead threads locks now explicitly require that signals are masked. o Access to the isdead field of the pthread structure is protected by both the active and dead list locks for writing. Either one is sufficient for reading. o The thread state and type fields have been combined into one three-state switch to make it easier to read without requiring a lock. It doesn't need a lock for writing (and therefore for reading either) because only the current thread can write to it and it is an integer value. o The thread state field of the pthread structure has been eliminated. It was an unnecessary field that mostly duplicated the flags field, but required additional locking that would make a lot more code paths require signal masking. Any truly unique values (such as PS_DEAD) have been reborn as separate members of the pthread structure. o Since the mutex and condvar pthread functions are not async-signal-safe there is no need to muck about with the wait queues when handling a signal ... o ... which also removes the need for wrapping signal handlers and sigaction(2). o The condvar and mutex async-cancellation code had to be revised as a result of some of these changes, which resulted in semi-unrelated changes which would have been difficult to work on as a separate commit, so they are included as well. The only part of the changes I am worried about is related to locking for the pthread joining fields. But, I will take a closer look at them once this mega-patch is committed.
2004-05-20 12:06:16 +00:00
_thread_sigunblock();
- Add libthr but don't hook it up to the regular build yet. This is an adaptation of libc_r for the thr system call interface. This is beta quality code.
2003-04-01 03:46:29 +00:00
ret = ESRCH;
goto out;
}
o Don't explicitly check the thread for NULL. That is the caller's responsibility. o If a thread is not joinable, the correct return value is EINVAL.
2004-03-29 13:53:43 +00:00
if ((pthread->attr.flags & PTHREAD_DETACHED) != 0) {
Make libthr async-signal-safe without costly signal masking. The guidlines I followed are: Only 3 functions (pthread_cancel, pthread_setcancelstate, pthread_setcanceltype) are required to be async-signal-safe by POSIX. None of the rest of the pthread api is required to be async-signal-safe. This means that only the three mentioned functions are safe to use from inside signal handlers. However, there are certain system/libc calls that are cancellation points that a caller may call from within a signal handler, and since they are cancellation points calls have to be made into libthr to test for cancellation and exit the thread if necessary. So, the cancellation test and thread exit code paths must be async-signal-safe as well. A summary of the changes follows: o Almost all of the code paths that masked signals, as well as locking the pthread structure now lock only the pthread structure. o Signals are masked (and left that way) as soon as a thread enters pthread_exit(). o The active and dead threads locks now explicitly require that signals are masked. o Access to the isdead field of the pthread structure is protected by both the active and dead list locks for writing. Either one is sufficient for reading. o The thread state and type fields have been combined into one three-state switch to make it easier to read without requiring a lock. It doesn't need a lock for writing (and therefore for reading either) because only the current thread can write to it and it is an integer value. o The thread state field of the pthread structure has been eliminated. It was an unnecessary field that mostly duplicated the flags field, but required additional locking that would make a lot more code paths require signal masking. Any truly unique values (such as PS_DEAD) have been reborn as separate members of the pthread structure. o Since the mutex and condvar pthread functions are not async-signal-safe there is no need to muck about with the wait queues when handling a signal ... o ... which also removes the need for wrapping signal handlers and sigaction(2). o The condvar and mutex async-cancellation code had to be revised as a result of some of these changes, which resulted in semi-unrelated changes which would have been difficult to work on as a separate commit, so they are included as well. The only part of the changes I am worried about is related to locking for the pthread joining fields. But, I will take a closer look at them once this mega-patch is committed.
2004-05-20 12:06:16 +00:00
PTHREAD_UNLOCK(pthread);
o Don't explicitly check the thread for NULL. That is the caller's responsibility. o If a thread is not joinable, the correct return value is EINVAL.
2004-03-29 13:53:43 +00:00
THREAD_LIST_UNLOCK;
DEAD_LIST_UNLOCK;
Make libthr async-signal-safe without costly signal masking. The guidlines I followed are: Only 3 functions (pthread_cancel, pthread_setcancelstate, pthread_setcanceltype) are required to be async-signal-safe by POSIX. None of the rest of the pthread api is required to be async-signal-safe. This means that only the three mentioned functions are safe to use from inside signal handlers. However, there are certain system/libc calls that are cancellation points that a caller may call from within a signal handler, and since they are cancellation points calls have to be made into libthr to test for cancellation and exit the thread if necessary. So, the cancellation test and thread exit code paths must be async-signal-safe as well. A summary of the changes follows: o Almost all of the code paths that masked signals, as well as locking the pthread structure now lock only the pthread structure. o Signals are masked (and left that way) as soon as a thread enters pthread_exit(). o The active and dead threads locks now explicitly require that signals are masked. o Access to the isdead field of the pthread structure is protected by both the active and dead list locks for writing. Either one is sufficient for reading. o The thread state and type fields have been combined into one three-state switch to make it easier to read without requiring a lock. It doesn't need a lock for writing (and therefore for reading either) because only the current thread can write to it and it is an integer value. o The thread state field of the pthread structure has been eliminated. It was an unnecessary field that mostly duplicated the flags field, but required additional locking that would make a lot more code paths require signal masking. Any truly unique values (such as PS_DEAD) have been reborn as separate members of the pthread structure. o Since the mutex and condvar pthread functions are not async-signal-safe there is no need to muck about with the wait queues when handling a signal ... o ... which also removes the need for wrapping signal handlers and sigaction(2). o The condvar and mutex async-cancellation code had to be revised as a result of some of these changes, which resulted in semi-unrelated changes which would have been difficult to work on as a separate commit, so they are included as well. The only part of the changes I am worried about is related to locking for the pthread joining fields. But, I will take a closer look at them once this mega-patch is committed.
2004-05-20 12:06:16 +00:00
_thread_sigunblock();
o Don't explicitly check the thread for NULL. That is the caller's responsibility. o If a thread is not joinable, the correct return value is EINVAL.
2004-03-29 13:53:43 +00:00
ret = EINVAL;
goto out;
}
- Add libthr but don't hook it up to the regular build yet. This is an adaptation of libc_r for the thr system call interface. This is beta quality code.
2003-04-01 03:46:29 +00:00
if (pthread->joiner != NULL) {
/* Multiple joiners are not supported. */
/* XXXTHR - support multiple joiners. */
Make libthr async-signal-safe without costly signal masking. The guidlines I followed are: Only 3 functions (pthread_cancel, pthread_setcancelstate, pthread_setcanceltype) are required to be async-signal-safe by POSIX. None of the rest of the pthread api is required to be async-signal-safe. This means that only the three mentioned functions are safe to use from inside signal handlers. However, there are certain system/libc calls that are cancellation points that a caller may call from within a signal handler, and since they are cancellation points calls have to be made into libthr to test for cancellation and exit the thread if necessary. So, the cancellation test and thread exit code paths must be async-signal-safe as well. A summary of the changes follows: o Almost all of the code paths that masked signals, as well as locking the pthread structure now lock only the pthread structure. o Signals are masked (and left that way) as soon as a thread enters pthread_exit(). o The active and dead threads locks now explicitly require that signals are masked. o Access to the isdead field of the pthread structure is protected by both the active and dead list locks for writing. Either one is sufficient for reading. o The thread state and type fields have been combined into one three-state switch to make it easier to read without requiring a lock. It doesn't need a lock for writing (and therefore for reading either) because only the current thread can write to it and it is an integer value. o The thread state field of the pthread structure has been eliminated. It was an unnecessary field that mostly duplicated the flags field, but required additional locking that would make a lot more code paths require signal masking. Any truly unique values (such as PS_DEAD) have been reborn as separate members of the pthread structure. o Since the mutex and condvar pthread functions are not async-signal-safe there is no need to muck about with the wait queues when handling a signal ... o ... which also removes the need for wrapping signal handlers and sigaction(2). o The condvar and mutex async-cancellation code had to be revised as a result of some of these changes, which resulted in semi-unrelated changes which would have been difficult to work on as a separate commit, so they are included as well. The only part of the changes I am worried about is related to locking for the pthread joining fields. But, I will take a closer look at them once this mega-patch is committed.
2004-05-20 12:06:16 +00:00
PTHREAD_UNLOCK(pthread);
Revise the unlock order in _pthread_join(). Also, if the joined thread is not dead, the join loop is guaranteed to execute at least once, so there is no need to pick up the thread list lock after we return from suspenstion only to release it after the loop. Approved by: re/blanket libthr
2003-05-26 00:28:49 +00:00
THREAD_LIST_UNLOCK;
Start locking up the active and dead threads lists. The active threads list is protected by a spinlock_t, but the dead list uses a pthread_mutex because it is necessary to synchronize other threads with the garbage collector thread. Lock/Unlock macros are used so it's easier to make changes to the locks in the future. The 'dead thread list' lock is intended to replace the gc mutex. This doesn't have any practical ramifications. It simply makes it clearer what the purpose of the lock is. The gc will use this lock, instead of the gc mutex, to synchronize access to the dead list with other threads. Modify _pthread_exit() to use these two new locks instead of GIANT_LOCK, and also to properly lock and protect thread state changes, especially with respect to a joining thread. The gc thread was also re-arranged to be more organized and less nested. _pthread_join() was also modified to use the thread list locks. However, locking and unlocking here needs special care because a thread could find itself in a position where it's joining an exiting thread that is waiting on the dead list lock, which this thread (joiner) holds. If the joiner doesn't take care to lock *and* unlock in the same order they (the joiner and the joinee) could deadlock against each other. Approved by: re/blanket libthr
2003-05-25 08:31:33 +00:00
DEAD_LIST_UNLOCK;
Make libthr async-signal-safe without costly signal masking. The guidlines I followed are: Only 3 functions (pthread_cancel, pthread_setcancelstate, pthread_setcanceltype) are required to be async-signal-safe by POSIX. None of the rest of the pthread api is required to be async-signal-safe. This means that only the three mentioned functions are safe to use from inside signal handlers. However, there are certain system/libc calls that are cancellation points that a caller may call from within a signal handler, and since they are cancellation points calls have to be made into libthr to test for cancellation and exit the thread if necessary. So, the cancellation test and thread exit code paths must be async-signal-safe as well. A summary of the changes follows: o Almost all of the code paths that masked signals, as well as locking the pthread structure now lock only the pthread structure. o Signals are masked (and left that way) as soon as a thread enters pthread_exit(). o The active and dead threads locks now explicitly require that signals are masked. o Access to the isdead field of the pthread structure is protected by both the active and dead list locks for writing. Either one is sufficient for reading. o The thread state and type fields have been combined into one three-state switch to make it easier to read without requiring a lock. It doesn't need a lock for writing (and therefore for reading either) because only the current thread can write to it and it is an integer value. o The thread state field of the pthread structure has been eliminated. It was an unnecessary field that mostly duplicated the flags field, but required additional locking that would make a lot more code paths require signal masking. Any truly unique values (such as PS_DEAD) have been reborn as separate members of the pthread structure. o Since the mutex and condvar pthread functions are not async-signal-safe there is no need to muck about with the wait queues when handling a signal ... o ... which also removes the need for wrapping signal handlers and sigaction(2). o The condvar and mutex async-cancellation code had to be revised as a result of some of these changes, which resulted in semi-unrelated changes which would have been difficult to work on as a separate commit, so they are included as well. The only part of the changes I am worried about is related to locking for the pthread joining fields. But, I will take a closer look at them once this mega-patch is committed.
2004-05-20 12:06:16 +00:00
_thread_sigunblock();
- Add libthr but don't hook it up to the regular build yet. This is an adaptation of libc_r for the thr system call interface. This is beta quality code.
2003-04-01 03:46:29 +00:00
ret = ENOTSUP;
goto out;
}
Move a misplaced comment. Approved by: markm/mentor (implicit), re/blanket libthr
2003-05-20 18:48:41 +00:00
/* Check if the thread is not dead: */
1. Now that it's a thread's state is changed from within the kernel, where no userland locks are heald, the dead thread lock can no longer protect access to it. Therefore, instead of using an if (!dead)...else clause after walking the active threads list test the thread pointer before deciding not to walk the dead threads list. If the thread pointer is null it means it was not found in the active threads list and the dead threads list should be checked. 2. Do not free the stack of a thread that is not marked dead. This is the 2nd and final part of eliminating the race to free a thread's stack. MFC after: 3 days
2004-10-13 11:42:20 +00:00
if (!dead) {
- Add libthr but don't hook it up to the regular build yet. This is an adaptation of libc_r for the thr system call interface. This is beta quality code.
2003-04-01 03:46:29 +00:00
/* Set the running thread to be the joiner: */
pthread->joiner = curthread;
Make libthr async-signal-safe without costly signal masking. The guidlines I followed are: Only 3 functions (pthread_cancel, pthread_setcancelstate, pthread_setcanceltype) are required to be async-signal-safe by POSIX. None of the rest of the pthread api is required to be async-signal-safe. This means that only the three mentioned functions are safe to use from inside signal handlers. However, there are certain system/libc calls that are cancellation points that a caller may call from within a signal handler, and since they are cancellation points calls have to be made into libthr to test for cancellation and exit the thread if necessary. So, the cancellation test and thread exit code paths must be async-signal-safe as well. A summary of the changes follows: o Almost all of the code paths that masked signals, as well as locking the pthread structure now lock only the pthread structure. o Signals are masked (and left that way) as soon as a thread enters pthread_exit(). o The active and dead threads locks now explicitly require that signals are masked. o Access to the isdead field of the pthread structure is protected by both the active and dead list locks for writing. Either one is sufficient for reading. o The thread state and type fields have been combined into one three-state switch to make it easier to read without requiring a lock. It doesn't need a lock for writing (and therefore for reading either) because only the current thread can write to it and it is an integer value. o The thread state field of the pthread structure has been eliminated. It was an unnecessary field that mostly duplicated the flags field, but required additional locking that would make a lot more code paths require signal masking. Any truly unique values (such as PS_DEAD) have been reborn as separate members of the pthread structure. o Since the mutex and condvar pthread functions are not async-signal-safe there is no need to muck about with the wait queues when handling a signal ... o ... which also removes the need for wrapping signal handlers and sigaction(2). o The condvar and mutex async-cancellation code had to be revised as a result of some of these changes, which resulted in semi-unrelated changes which would have been difficult to work on as a separate commit, so they are included as well. The only part of the changes I am worried about is related to locking for the pthread joining fields. But, I will take a closer look at them once this mega-patch is committed.
2004-05-20 12:06:16 +00:00
PTHREAD_UNLOCK(pthread);
- Add libthr but don't hook it up to the regular build yet. This is an adaptation of libc_r for the thr system call interface. This is beta quality code.
2003-04-01 03:46:29 +00:00
/* Keep track of which thread we're joining to: */
curthread->join_status.thread = pthread;
while (curthread->join_status.thread == pthread) {
/* Wait for our signal to wake up. */
Revise the unlock order in _pthread_join(). Also, if the joined thread is not dead, the join loop is guaranteed to execute at least once, so there is no need to pick up the thread list lock after we return from suspenstion only to release it after the loop. Approved by: re/blanket libthr
2003-05-26 00:28:49 +00:00
THREAD_LIST_UNLOCK;
Start locking up the active and dead threads lists. The active threads list is protected by a spinlock_t, but the dead list uses a pthread_mutex because it is necessary to synchronize other threads with the garbage collector thread. Lock/Unlock macros are used so it's easier to make changes to the locks in the future. The 'dead thread list' lock is intended to replace the gc mutex. This doesn't have any practical ramifications. It simply makes it clearer what the purpose of the lock is. The gc will use this lock, instead of the gc mutex, to synchronize access to the dead list with other threads. Modify _pthread_exit() to use these two new locks instead of GIANT_LOCK, and also to properly lock and protect thread state changes, especially with respect to a joining thread. The gc thread was also re-arranged to be more organized and less nested. _pthread_join() was also modified to use the thread list locks. However, locking and unlocking here needs special care because a thread could find itself in a position where it's joining an exiting thread that is waiting on the dead list lock, which this thread (joiner) holds. If the joiner doesn't take care to lock *and* unlock in the same order they (the joiner and the joinee) could deadlock against each other. Approved by: re/blanket libthr
2003-05-25 08:31:33 +00:00
DEAD_LIST_UNLOCK;
Make libthr async-signal-safe without costly signal masking. The guidlines I followed are: Only 3 functions (pthread_cancel, pthread_setcancelstate, pthread_setcanceltype) are required to be async-signal-safe by POSIX. None of the rest of the pthread api is required to be async-signal-safe. This means that only the three mentioned functions are safe to use from inside signal handlers. However, there are certain system/libc calls that are cancellation points that a caller may call from within a signal handler, and since they are cancellation points calls have to be made into libthr to test for cancellation and exit the thread if necessary. So, the cancellation test and thread exit code paths must be async-signal-safe as well. A summary of the changes follows: o Almost all of the code paths that masked signals, as well as locking the pthread structure now lock only the pthread structure. o Signals are masked (and left that way) as soon as a thread enters pthread_exit(). o The active and dead threads locks now explicitly require that signals are masked. o Access to the isdead field of the pthread structure is protected by both the active and dead list locks for writing. Either one is sufficient for reading. o The thread state and type fields have been combined into one three-state switch to make it easier to read without requiring a lock. It doesn't need a lock for writing (and therefore for reading either) because only the current thread can write to it and it is an integer value. o The thread state field of the pthread structure has been eliminated. It was an unnecessary field that mostly duplicated the flags field, but required additional locking that would make a lot more code paths require signal masking. Any truly unique values (such as PS_DEAD) have been reborn as separate members of the pthread structure. o Since the mutex and condvar pthread functions are not async-signal-safe there is no need to muck about with the wait queues when handling a signal ... o ... which also removes the need for wrapping signal handlers and sigaction(2). o The condvar and mutex async-cancellation code had to be revised as a result of some of these changes, which resulted in semi-unrelated changes which would have been difficult to work on as a separate commit, so they are included as well. The only part of the changes I am worried about is related to locking for the pthread joining fields. But, I will take a closer look at them once this mega-patch is committed.
2004-05-20 12:06:16 +00:00
_thread_sigunblock();
if (curthread->cancellation != CS_NULL)
pthread->joiner = NULL;
_thread_enter_cancellation_point();
/*
* XXX - Workaround to make a join a cancellation
* point. Must find a better solution.
*/
PTHREAD_LOCK(curthread);
curthread->flags |= PTHREAD_FLAGS_SUSPENDED;
PTHREAD_UNLOCK(curthread);
Catchup with _thread_suspend() changes.
2003-06-30 12:35:31 +00:00
ret = _thread_suspend(curthread, NULL);
if (ret != 0 && ret != EAGAIN && ret != EINTR)
PANIC("Unable to suspend in join.");
Make libthr async-signal-safe without costly signal masking. The guidlines I followed are: Only 3 functions (pthread_cancel, pthread_setcancelstate, pthread_setcanceltype) are required to be async-signal-safe by POSIX. None of the rest of the pthread api is required to be async-signal-safe. This means that only the three mentioned functions are safe to use from inside signal handlers. However, there are certain system/libc calls that are cancellation points that a caller may call from within a signal handler, and since they are cancellation points calls have to be made into libthr to test for cancellation and exit the thread if necessary. So, the cancellation test and thread exit code paths must be async-signal-safe as well. A summary of the changes follows: o Almost all of the code paths that masked signals, as well as locking the pthread structure now lock only the pthread structure. o Signals are masked (and left that way) as soon as a thread enters pthread_exit(). o The active and dead threads locks now explicitly require that signals are masked. o Access to the isdead field of the pthread structure is protected by both the active and dead list locks for writing. Either one is sufficient for reading. o The thread state and type fields have been combined into one three-state switch to make it easier to read without requiring a lock. It doesn't need a lock for writing (and therefore for reading either) because only the current thread can write to it and it is an integer value. o The thread state field of the pthread structure has been eliminated. It was an unnecessary field that mostly duplicated the flags field, but required additional locking that would make a lot more code paths require signal masking. Any truly unique values (such as PS_DEAD) have been reborn as separate members of the pthread structure. o Since the mutex and condvar pthread functions are not async-signal-safe there is no need to muck about with the wait queues when handling a signal ... o ... which also removes the need for wrapping signal handlers and sigaction(2). o The condvar and mutex async-cancellation code had to be revised as a result of some of these changes, which resulted in semi-unrelated changes which would have been difficult to work on as a separate commit, so they are included as well. The only part of the changes I am worried about is related to locking for the pthread joining fields. But, I will take a closer look at them once this mega-patch is committed.
2004-05-20 12:06:16 +00:00
PTHREAD_LOCK(curthread);
curthread->flags &= ~PTHREAD_FLAGS_SUSPENDED;
PTHREAD_UNLOCK(curthread);
if (curthread->cancellation != CS_NULL)
pthread->joiner = NULL;
_thread_leave_cancellation_point();
Revise the unlock order in _pthread_join(). Also, if the joined thread is not dead, the join loop is guaranteed to execute at least once, so there is no need to pick up the thread list lock after we return from suspenstion only to release it after the loop. Approved by: re/blanket libthr
2003-05-26 00:28:49 +00:00
Revert part of the last commit. I don't know what I was smoking. Approved by: re/rwatson
2003-05-27 21:43:49 +00:00
/*
* XXX - For correctness reasons.
* We must aquire these in the same order and also
Make libthr async-signal-safe without costly signal masking. The guidlines I followed are: Only 3 functions (pthread_cancel, pthread_setcancelstate, pthread_setcanceltype) are required to be async-signal-safe by POSIX. None of the rest of the pthread api is required to be async-signal-safe. This means that only the three mentioned functions are safe to use from inside signal handlers. However, there are certain system/libc calls that are cancellation points that a caller may call from within a signal handler, and since they are cancellation points calls have to be made into libthr to test for cancellation and exit the thread if necessary. So, the cancellation test and thread exit code paths must be async-signal-safe as well. A summary of the changes follows: o Almost all of the code paths that masked signals, as well as locking the pthread structure now lock only the pthread structure. o Signals are masked (and left that way) as soon as a thread enters pthread_exit(). o The active and dead threads locks now explicitly require that signals are masked. o Access to the isdead field of the pthread structure is protected by both the active and dead list locks for writing. Either one is sufficient for reading. o The thread state and type fields have been combined into one three-state switch to make it easier to read without requiring a lock. It doesn't need a lock for writing (and therefore for reading either) because only the current thread can write to it and it is an integer value. o The thread state field of the pthread structure has been eliminated. It was an unnecessary field that mostly duplicated the flags field, but required additional locking that would make a lot more code paths require signal masking. Any truly unique values (such as PS_DEAD) have been reborn as separate members of the pthread structure. o Since the mutex and condvar pthread functions are not async-signal-safe there is no need to muck about with the wait queues when handling a signal ... o ... which also removes the need for wrapping signal handlers and sigaction(2). o The condvar and mutex async-cancellation code had to be revised as a result of some of these changes, which resulted in semi-unrelated changes which would have been difficult to work on as a separate commit, so they are included as well. The only part of the changes I am worried about is related to locking for the pthread joining fields. But, I will take a closer look at them once this mega-patch is committed.
2004-05-20 12:06:16 +00:00
* importantly, release in the same order because
Revert part of the last commit. I don't know what I was smoking. Approved by: re/rwatson
2003-05-27 21:43:49 +00:00
* otherwise we might deadlock with the joined thread
* when we attempt to release one of these locks.
*/
Make libthr async-signal-safe without costly signal masking. The guidlines I followed are: Only 3 functions (pthread_cancel, pthread_setcancelstate, pthread_setcanceltype) are required to be async-signal-safe by POSIX. None of the rest of the pthread api is required to be async-signal-safe. This means that only the three mentioned functions are safe to use from inside signal handlers. However, there are certain system/libc calls that are cancellation points that a caller may call from within a signal handler, and since they are cancellation points calls have to be made into libthr to test for cancellation and exit the thread if necessary. So, the cancellation test and thread exit code paths must be async-signal-safe as well. A summary of the changes follows: o Almost all of the code paths that masked signals, as well as locking the pthread structure now lock only the pthread structure. o Signals are masked (and left that way) as soon as a thread enters pthread_exit(). o The active and dead threads locks now explicitly require that signals are masked. o Access to the isdead field of the pthread structure is protected by both the active and dead list locks for writing. Either one is sufficient for reading. o The thread state and type fields have been combined into one three-state switch to make it easier to read without requiring a lock. It doesn't need a lock for writing (and therefore for reading either) because only the current thread can write to it and it is an integer value. o The thread state field of the pthread structure has been eliminated. It was an unnecessary field that mostly duplicated the flags field, but required additional locking that would make a lot more code paths require signal masking. Any truly unique values (such as PS_DEAD) have been reborn as separate members of the pthread structure. o Since the mutex and condvar pthread functions are not async-signal-safe there is no need to muck about with the wait queues when handling a signal ... o ... which also removes the need for wrapping signal handlers and sigaction(2). o The condvar and mutex async-cancellation code had to be revised as a result of some of these changes, which resulted in semi-unrelated changes which would have been difficult to work on as a separate commit, so they are included as well. The only part of the changes I am worried about is related to locking for the pthread joining fields. But, I will take a closer look at them once this mega-patch is committed.
2004-05-20 12:06:16 +00:00
_thread_sigblock();
Revert part of the last commit. I don't know what I was smoking. Approved by: re/rwatson
2003-05-27 21:43:49 +00:00
DEAD_LIST_LOCK;
THREAD_LIST_LOCK;
- Add libthr but don't hook it up to the regular build yet. This is an adaptation of libc_r for the thr system call interface. This is beta quality code.
2003-04-01 03:46:29 +00:00
}
/*
* The thread return value and error are set by the thread we're
* joining to when it exits or detaches:
*/
ret = curthread->join_status.error;
if ((ret == 0) && (thread_return != NULL))
*thread_return = curthread->join_status.ret;
Revert part of the last commit. I don't know what I was smoking. Approved by: re/rwatson
2003-05-27 21:43:49 +00:00
THREAD_LIST_UNLOCK;
DEAD_LIST_UNLOCK;
Make libthr async-signal-safe without costly signal masking. The guidlines I followed are: Only 3 functions (pthread_cancel, pthread_setcancelstate, pthread_setcanceltype) are required to be async-signal-safe by POSIX. None of the rest of the pthread api is required to be async-signal-safe. This means that only the three mentioned functions are safe to use from inside signal handlers. However, there are certain system/libc calls that are cancellation points that a caller may call from within a signal handler, and since they are cancellation points calls have to be made into libthr to test for cancellation and exit the thread if necessary. So, the cancellation test and thread exit code paths must be async-signal-safe as well. A summary of the changes follows: o Almost all of the code paths that masked signals, as well as locking the pthread structure now lock only the pthread structure. o Signals are masked (and left that way) as soon as a thread enters pthread_exit(). o The active and dead threads locks now explicitly require that signals are masked. o Access to the isdead field of the pthread structure is protected by both the active and dead list locks for writing. Either one is sufficient for reading. o The thread state and type fields have been combined into one three-state switch to make it easier to read without requiring a lock. It doesn't need a lock for writing (and therefore for reading either) because only the current thread can write to it and it is an integer value. o The thread state field of the pthread structure has been eliminated. It was an unnecessary field that mostly duplicated the flags field, but required additional locking that would make a lot more code paths require signal masking. Any truly unique values (such as PS_DEAD) have been reborn as separate members of the pthread structure. o Since the mutex and condvar pthread functions are not async-signal-safe there is no need to muck about with the wait queues when handling a signal ... o ... which also removes the need for wrapping signal handlers and sigaction(2). o The condvar and mutex async-cancellation code had to be revised as a result of some of these changes, which resulted in semi-unrelated changes which would have been difficult to work on as a separate commit, so they are included as well. The only part of the changes I am worried about is related to locking for the pthread joining fields. But, I will take a closer look at them once this mega-patch is committed.
2004-05-20 12:06:16 +00:00
_thread_sigunblock();
- Add libthr but don't hook it up to the regular build yet. This is an adaptation of libc_r for the thr system call interface. This is beta quality code.
2003-04-01 03:46:29 +00:00
} else {
/*
* The thread exited (is dead) without being detached, and no
* thread has joined it.
*/
/* Check if the return value is required: */
if (thread_return != NULL) {
/* Return the thread's return value: */
*thread_return = pthread->ret;
}
Remove the garbage collector thread. All resources are freed in-line. If the exiting thread cannot release a resource, then the next thread to exit will release it.
2004-03-28 14:05:28 +00:00
/* Free all remaining memory allocated to the thread. */
- Add libthr but don't hook it up to the regular build yet. This is an adaptation of libc_r for the thr system call interface. This is beta quality code.
2003-04-01 03:46:29 +00:00
pthread->attr.flags |= PTHREAD_DETACHED;
Make libthr async-signal-safe without costly signal masking. The guidlines I followed are: Only 3 functions (pthread_cancel, pthread_setcancelstate, pthread_setcanceltype) are required to be async-signal-safe by POSIX. None of the rest of the pthread api is required to be async-signal-safe. This means that only the three mentioned functions are safe to use from inside signal handlers. However, there are certain system/libc calls that are cancellation points that a caller may call from within a signal handler, and since they are cancellation points calls have to be made into libthr to test for cancellation and exit the thread if necessary. So, the cancellation test and thread exit code paths must be async-signal-safe as well. A summary of the changes follows: o Almost all of the code paths that masked signals, as well as locking the pthread structure now lock only the pthread structure. o Signals are masked (and left that way) as soon as a thread enters pthread_exit(). o The active and dead threads locks now explicitly require that signals are masked. o Access to the isdead field of the pthread structure is protected by both the active and dead list locks for writing. Either one is sufficient for reading. o The thread state and type fields have been combined into one three-state switch to make it easier to read without requiring a lock. It doesn't need a lock for writing (and therefore for reading either) because only the current thread can write to it and it is an integer value. o The thread state field of the pthread structure has been eliminated. It was an unnecessary field that mostly duplicated the flags field, but required additional locking that would make a lot more code paths require signal masking. Any truly unique values (such as PS_DEAD) have been reborn as separate members of the pthread structure. o Since the mutex and condvar pthread functions are not async-signal-safe there is no need to muck about with the wait queues when handling a signal ... o ... which also removes the need for wrapping signal handlers and sigaction(2). o The condvar and mutex async-cancellation code had to be revised as a result of some of these changes, which resulted in semi-unrelated changes which would have been difficult to work on as a separate commit, so they are included as well. The only part of the changes I am worried about is related to locking for the pthread joining fields. But, I will take a closer look at them once this mega-patch is committed.
2004-05-20 12:06:16 +00:00
PTHREAD_UNLOCK(pthread);
Remove the garbage collector thread. All resources are freed in-line. If the exiting thread cannot release a resource, then the next thread to exit will release it.
2004-03-28 14:05:28 +00:00
TAILQ_REMOVE(&_dead_list, pthread, dle);
deadlist_free_onethread(pthread);
Don't hold the active thread list lock when signaling the gc thread. The dead list thread is sufficient for synchronization. Retire the arch_id (ldt array slot) in the gc thread instead of the doing it in the thread itself. Approved by: re/jhb
2003-05-29 20:46:53 +00:00
THREAD_LIST_UNLOCK;
Start locking up the active and dead threads lists. The active threads list is protected by a spinlock_t, but the dead list uses a pthread_mutex because it is necessary to synchronize other threads with the garbage collector thread. Lock/Unlock macros are used so it's easier to make changes to the locks in the future. The 'dead thread list' lock is intended to replace the gc mutex. This doesn't have any practical ramifications. It simply makes it clearer what the purpose of the lock is. The gc will use this lock, instead of the gc mutex, to synchronize access to the dead list with other threads. Modify _pthread_exit() to use these two new locks instead of GIANT_LOCK, and also to properly lock and protect thread state changes, especially with respect to a joining thread. The gc thread was also re-arranged to be more organized and less nested. _pthread_join() was also modified to use the thread list locks. However, locking and unlocking here needs special care because a thread could find itself in a position where it's joining an exiting thread that is waiting on the dead list lock, which this thread (joiner) holds. If the joiner doesn't take care to lock *and* unlock in the same order they (the joiner and the joinee) could deadlock against each other. Approved by: re/blanket libthr
2003-05-25 08:31:33 +00:00
DEAD_LIST_UNLOCK;
Make libthr async-signal-safe without costly signal masking. The guidlines I followed are: Only 3 functions (pthread_cancel, pthread_setcancelstate, pthread_setcanceltype) are required to be async-signal-safe by POSIX. None of the rest of the pthread api is required to be async-signal-safe. This means that only the three mentioned functions are safe to use from inside signal handlers. However, there are certain system/libc calls that are cancellation points that a caller may call from within a signal handler, and since they are cancellation points calls have to be made into libthr to test for cancellation and exit the thread if necessary. So, the cancellation test and thread exit code paths must be async-signal-safe as well. A summary of the changes follows: o Almost all of the code paths that masked signals, as well as locking the pthread structure now lock only the pthread structure. o Signals are masked (and left that way) as soon as a thread enters pthread_exit(). o The active and dead threads locks now explicitly require that signals are masked. o Access to the isdead field of the pthread structure is protected by both the active and dead list locks for writing. Either one is sufficient for reading. o The thread state and type fields have been combined into one three-state switch to make it easier to read without requiring a lock. It doesn't need a lock for writing (and therefore for reading either) because only the current thread can write to it and it is an integer value. o The thread state field of the pthread structure has been eliminated. It was an unnecessary field that mostly duplicated the flags field, but required additional locking that would make a lot more code paths require signal masking. Any truly unique values (such as PS_DEAD) have been reborn as separate members of the pthread structure. o Since the mutex and condvar pthread functions are not async-signal-safe there is no need to muck about with the wait queues when handling a signal ... o ... which also removes the need for wrapping signal handlers and sigaction(2). o The condvar and mutex async-cancellation code had to be revised as a result of some of these changes, which resulted in semi-unrelated changes which would have been difficult to work on as a separate commit, so they are included as well. The only part of the changes I am worried about is related to locking for the pthread joining fields. But, I will take a closer look at them once this mega-patch is committed.
2004-05-20 12:06:16 +00:00
_thread_sigunblock();
- Add libthr but don't hook it up to the regular build yet. This is an adaptation of libc_r for the thr system call interface. This is beta quality code.
2003-04-01 03:46:29 +00:00
}
out:
_thread_leave_cancellation_point();
/* Return the completion status: */
return (ret);
}
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