2003-04-01 03:46:29 +00:00
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/*
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2005-12-17 09:42:45 +00:00
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* Copyright (c) 2005, David Xu <davidxu@freebsd.org>
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2003-04-01 03:46:29 +00:00
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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2005-12-17 09:42:45 +00:00
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* notice unmodified, this list of conditions, and the following
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* disclaimer.
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2003-04-01 03:46:29 +00:00
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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2005-12-17 09:42:45 +00:00
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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2003-04-01 03:46:29 +00:00
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*
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* $FreeBSD$
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2005-12-17 09:42:45 +00:00
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*
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2003-04-01 03:46:29 +00:00
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*/
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2005-04-02 01:20:00 +00:00
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2006-04-04 02:57:49 +00:00
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#include "namespace.h"
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2003-04-01 03:46:29 +00:00
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#include <errno.h>
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#include <pthread.h>
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2006-04-04 02:57:49 +00:00
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#include "un-namespace.h"
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2005-04-02 01:20:00 +00:00
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2003-04-01 03:46:29 +00:00
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#include "thr_private.h"
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2006-04-04 02:57:49 +00:00
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int _pthread_timedjoin_np(pthread_t pthread, void **thread_return,
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const struct timespec *abstime);
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2005-10-04 06:15:25 +00:00
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static int join_common(pthread_t, void **, const struct timespec *);
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2003-04-01 03:46:29 +00:00
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__weak_reference(_pthread_join, pthread_join);
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2005-10-04 06:15:25 +00:00
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__weak_reference(_pthread_timedjoin_np, pthread_timedjoin_np);
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2003-04-01 03:46:29 +00:00
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2005-04-02 01:20:00 +00:00
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static void backout_join(void *arg)
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{
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struct pthread *pthread = (struct pthread *)arg;
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2010-09-13 07:03:01 +00:00
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struct pthread *curthread = _get_curthread();
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2005-04-02 01:20:00 +00:00
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2010-09-13 07:03:01 +00:00
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THR_THREAD_LOCK(curthread, pthread);
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2005-04-02 01:20:00 +00:00
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pthread->joiner = NULL;
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2010-09-19 08:55:36 +00:00
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THR_THREAD_UNLOCK(curthread, pthread);
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2005-04-02 01:20:00 +00:00
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}
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2003-04-01 03:46:29 +00:00
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int
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_pthread_join(pthread_t pthread, void **thread_return)
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2005-10-04 06:15:25 +00:00
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{
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return (join_common(pthread, thread_return, NULL));
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}
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int
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_pthread_timedjoin_np(pthread_t pthread, void **thread_return,
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const struct timespec *abstime)
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{
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if (abstime == NULL || abstime->tv_sec < 0 || abstime->tv_nsec < 0 ||
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abstime->tv_nsec >= 1000000000)
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return (EINVAL);
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return (join_common(pthread, thread_return, abstime));
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}
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In current implementation, thread cancellation is done in signal handler,
which does not know what is the state of interrupted system call, for
example, open() system call opened a file and the thread is still cancelled,
result is descriptor leak, there are other problems which can cause resource
leak or undeterminable side effect when a thread is cancelled. However, this
is no longer true in new implementation.
In defering mode, a thread is canceled if cancellation request is pending and
later the thread enters a cancellation point, otherwise, a later
pthread_cancel() just causes SIGCANCEL to be sent to the target thread, and
causes target thread to abort system call, userland code in libthr then checks
cancellation state, and cancels the thread if needed. For example, the
cancellation point open(), the thread may be canceled at start,
but later, if it opened a file descriptor, it is not canceled, this avoids
file handle leak. Another example is read(), a thread may be canceled at start
of the function, but later, if it read some bytes from a socket, the thread
is not canceled, the caller then can decide if it should still enable cancelling
or disable it and continue reading data until it thinks it has read all
bytes of a packet, and keeps a protocol stream in health state, if user ignores
partly reading of a packet without disabling cancellation, then second iteration
of read loop cause the thread to be cancelled.
An exception is that the close() cancellation point always closes a file handle
despite whether the thread is cancelled or not.
The old mechanism is still kept, for a functions which is not so easily to
fix a cancellation problem, the rough mechanism is used.
Reviewed by: kib@
2010-08-20 05:15:39 +00:00
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/*
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* Cancellation behavior:
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* if the thread is canceled, joinee is not recycled.
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*/
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2005-10-04 06:15:25 +00:00
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static int
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join_common(pthread_t pthread, void **thread_return,
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const struct timespec *abstime)
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2003-04-01 03:46:29 +00:00
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{
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2005-04-02 01:20:00 +00:00
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struct pthread *curthread = _get_curthread();
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2005-10-04 06:15:25 +00:00
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struct timespec ts, ts2, *tsp;
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2005-04-02 01:20:00 +00:00
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void *tmp;
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2005-10-26 07:11:43 +00:00
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long tid;
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2005-04-02 01:20:00 +00:00
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int ret = 0;
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2005-10-26 07:11:43 +00:00
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2005-04-02 01:20:00 +00:00
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if (pthread == NULL)
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return (EINVAL);
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2003-04-01 03:46:29 +00:00
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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
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if (pthread == curthread)
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2005-04-02 01:20:00 +00:00
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return (EDEADLK);
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2003-04-01 03:46:29 +00:00
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2010-09-13 07:03:01 +00:00
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if ((ret = _thr_find_thread(curthread, pthread, 1)) != 0)
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return (ESRCH);
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if ((pthread->flags & THR_FLAGS_DETACHED) != 0) {
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2006-11-28 11:05:31 +00:00
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ret = EINVAL;
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2005-04-02 01:20:00 +00:00
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} else if (pthread->joiner != NULL) {
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2003-04-01 03:46:29 +00:00
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/* Multiple joiners are not supported. */
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ret = ENOTSUP;
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}
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2005-04-02 01:20:00 +00:00
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if (ret) {
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2010-09-13 07:03:01 +00:00
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THR_THREAD_UNLOCK(curthread, pthread);
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2005-04-02 01:20:00 +00:00
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return (ret);
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}
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/* Set the running thread to be the joiner: */
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pthread->joiner = curthread;
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2003-04-01 03:46:29 +00:00
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2010-09-13 07:03:01 +00:00
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THR_THREAD_UNLOCK(curthread, pthread);
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2003-05-26 00:28:49 +00:00
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2005-04-02 01:20:00 +00:00
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THR_CLEANUP_PUSH(curthread, backout_join, pthread);
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Add signal handler wrapper, the reason to add it becauses there are
some cases we want to improve:
1) if a thread signal got a signal while in cancellation point,
it is possible the TDP_WAKEUP may be eaten by signal handler
if the handler called some interruptibly system calls.
2) In signal handler, we want to disable cancellation.
3) When thread holding some low level locks, it is better to
disable signal, those code need not to worry reentrancy,
sigprocmask system call is avoided because it is a bit expensive.
The signal handler wrapper works in this way:
1) libthr installs its signal handler if user code invokes sigaction
to install its handler, the user handler is recorded in internal
array.
2) when a signal is delivered, libthr's signal handler is invoke,
libthr checks if thread holds some low level lock or is in critical
region, if it is true, the signal is buffered, and all signals are
masked, once the thread leaves critical region, correct signal
mask is restored and buffered signal is processed.
3) before user signal handler is invoked, cancellation is temporarily
disabled, after user signal handler is returned, cancellation state
is restored, and pending cancellation is rescheduled.
2010-09-01 02:18:33 +00:00
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_thr_cancel_enter(curthread);
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2003-04-01 03:46:29 +00:00
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2005-10-26 07:11:43 +00:00
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tid = pthread->tid;
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while (pthread->tid != TID_TERMINATED) {
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In current implementation, thread cancellation is done in signal handler,
which does not know what is the state of interrupted system call, for
example, open() system call opened a file and the thread is still cancelled,
result is descriptor leak, there are other problems which can cause resource
leak or undeterminable side effect when a thread is cancelled. However, this
is no longer true in new implementation.
In defering mode, a thread is canceled if cancellation request is pending and
later the thread enters a cancellation point, otherwise, a later
pthread_cancel() just causes SIGCANCEL to be sent to the target thread, and
causes target thread to abort system call, userland code in libthr then checks
cancellation state, and cancels the thread if needed. For example, the
cancellation point open(), the thread may be canceled at start,
but later, if it opened a file descriptor, it is not canceled, this avoids
file handle leak. Another example is read(), a thread may be canceled at start
of the function, but later, if it read some bytes from a socket, the thread
is not canceled, the caller then can decide if it should still enable cancelling
or disable it and continue reading data until it thinks it has read all
bytes of a packet, and keeps a protocol stream in health state, if user ignores
partly reading of a packet without disabling cancellation, then second iteration
of read loop cause the thread to be cancelled.
An exception is that the close() cancellation point always closes a file handle
despite whether the thread is cancelled or not.
The old mechanism is still kept, for a functions which is not so easily to
fix a cancellation problem, the rough mechanism is used.
Reviewed by: kib@
2010-08-20 05:15:39 +00:00
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_thr_testcancel(curthread);
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2005-10-04 06:15:25 +00:00
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if (abstime != NULL) {
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clock_gettime(CLOCK_REALTIME, &ts);
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TIMESPEC_SUB(&ts2, abstime, &ts);
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if (ts2.tv_sec < 0) {
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ret = ETIMEDOUT;
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break;
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}
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tsp = &ts2;
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} else
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tsp = NULL;
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2005-10-26 07:11:43 +00:00
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ret = _thr_umtx_wait(&pthread->tid, tid, tsp);
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2005-10-04 06:15:25 +00:00
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if (ret == ETIMEDOUT)
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break;
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2005-04-02 01:20:00 +00:00
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}
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2003-04-01 03:46:29 +00:00
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Add signal handler wrapper, the reason to add it becauses there are
some cases we want to improve:
1) if a thread signal got a signal while in cancellation point,
it is possible the TDP_WAKEUP may be eaten by signal handler
if the handler called some interruptibly system calls.
2) In signal handler, we want to disable cancellation.
3) When thread holding some low level locks, it is better to
disable signal, those code need not to worry reentrancy,
sigprocmask system call is avoided because it is a bit expensive.
The signal handler wrapper works in this way:
1) libthr installs its signal handler if user code invokes sigaction
to install its handler, the user handler is recorded in internal
array.
2) when a signal is delivered, libthr's signal handler is invoke,
libthr checks if thread holds some low level lock or is in critical
region, if it is true, the signal is buffered, and all signals are
masked, once the thread leaves critical region, correct signal
mask is restored and buffered signal is processed.
3) before user signal handler is invoked, cancellation is temporarily
disabled, after user signal handler is returned, cancellation state
is restored, and pending cancellation is rescheduled.
2010-09-01 02:18:33 +00:00
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_thr_cancel_leave(curthread, 0);
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2005-04-02 01:20:00 +00:00
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THR_CLEANUP_POP(curthread, 0);
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2003-04-01 03:46:29 +00:00
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2005-10-04 06:15:25 +00:00
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if (ret == ETIMEDOUT) {
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2010-09-13 07:03:01 +00:00
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THR_THREAD_LOCK(curthread, pthread);
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2005-10-04 06:15:25 +00:00
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pthread->joiner = NULL;
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2010-09-13 07:03:01 +00:00
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THR_THREAD_UNLOCK(curthread, pthread);
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2005-10-04 06:15:25 +00:00
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} else {
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2005-12-19 03:20:55 +00:00
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ret = 0;
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2005-10-04 06:15:25 +00:00
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tmp = pthread->ret;
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2010-09-13 07:03:01 +00:00
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THR_THREAD_LOCK(curthread, pthread);
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pthread->flags |= THR_FLAGS_DETACHED;
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2005-10-04 06:15:25 +00:00
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pthread->joiner = NULL;
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2010-09-13 07:03:01 +00:00
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_thr_try_gc(curthread, pthread); /* thread lock released */
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2003-04-01 03:46:29 +00:00
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2005-10-04 06:15:25 +00:00
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if (thread_return != NULL)
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*thread_return = tmp;
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}
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2003-04-01 03:46:29 +00:00
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return (ret);
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}
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