d/freebsd-dev
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity
eb9dc34d8b
freebsd-dev/lib/libc_r/uthread/uthread_fd.c
John Birrell 58a7cc5d1b [ The author's description... ] 
o Runnable threads are now maintained in priority queues.  The
    implementation requires two things:

      1.) The priority queues must be protected during insertion
          and removal of threads.  Since the kernel scheduler
          must modify the priority queues, a spinlock for
          protection cannot be used.   The functions
          _thread_kern_sched_defer() and _thread_kern_sched_undefer()
          were added to {un}defer kernel scheduler activation.

      2.) A thread (active) priority change can be performed only
          when the thread is removed from the priority queue.  The
          implementation uses a threads active priority when
          inserting it into the queue.

    A by-product is that thread switches are much faster.  A
    separate queue is used for waiting and/or blocked threads,
    and it is searched at most 2 times in the kernel scheduler
    when there are active threads.  It should be possible to
    reduce this to once by combining polling of threads waiting
    on I/O with the loop that looks for timed out threads and
    the minimum timeout value.

  o Functions to defer kernel scheduler activation were added.  These
    are _thread_kern_sched_defer() and _thread_kern_sched_undefer()
    and may be called recursively.  These routines do not block the
    scheduling signal, but latch its occurrence.  The signal handler
    will not call the kernel scheduler when the running thread has
    deferred scheduling, but it will be called when running thread
    undefers scheduling.

  o Added support for _POSIX_THREAD_PRIORITY_SCHEDULING.  All the
    POSIX routines required by this should now be implemented.
    One note, SCHED_OTHER, SCHED_FIFO, and SCHED_RR are required
    to be defined by including pthread.h.  These defines are currently
    in sched.h.  I modified pthread.h to include sched.h but don't
    know if this is the proper thing to do.

  o Added support for priority protection and inheritence mutexes.
    This allows definition of _POSIX_THREAD_PRIO_PROTECT and
    _POSIX_THREAD_PRIO_INHERIT.

  o Added additional error checks required by POSIX for mutexes and
    condition variables.

  o Provided a wrapper for sigpending which is marked as a hidden
    syscall.

  o Added a non-portable function as a debugging aid to allow an
    application to monitor thread context switches.  An application
    can install a routine that gets called everytime a thread
    (explicitly created by the application) gets context switched.
    The routine gets passed the pthread IDs of the threads that are
    being switched in and out.

Submitted by: Dan Eischen <eischen@vigrid.com>

Changes by me:

  o Added a PS_SPINBLOCK state to deal with the priority inversion
    problem most often (I think) seen by threads calling malloc/free/realloc.

  o Dispatch signals to the running thread directly rather than at a
    context switch to avoid the situation where the switch never occurs.
1999-03-23 05:07:56 +00:00

722 lines
19 KiB
C
Raw Blame History

/*
* Copyright (c) 1995-1998 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 REGENTS 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.
*
* $Id: uthread_fd.c,v 1.9 1998/09/13 15:33:42 dt Exp $
*
*/
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#ifdef _THREAD_SAFE
#include <pthread.h>
#include "pthread_private.h"
/* Static variables: */
static spinlock_t fd_table_lock = _SPINLOCK_INITIALIZER;
/*
* This function *must* return -1 and set the thread specific errno
* as a system call. This is because the error return from this
* function is propagated directly back from thread-wrapped system
* calls.
*/
int
_thread_fd_table_init(int fd)
{
int ret = 0;
struct fd_table_entry *entry;
int saved_errno;
/* Check if the file descriptor is out of range: */
if (fd < 0 || fd >= _thread_dtablesize) {
/* Return a bad file descriptor error: */
errno = EBADF;
ret = -1;
}
/*
* Check if memory has already been allocated for this file
* descriptor:
*/
else if (_thread_fd_table[fd] != NULL) {
/* Memory has already been allocated. */
/* Allocate memory for the file descriptor table entry: */
} else if ((entry = (struct fd_table_entry *)
malloc(sizeof(struct fd_table_entry))) == NULL) {
/* Return an insufficient memory error: */
errno = ENOMEM;
ret = -1;
} else {
/* Initialise the file locks: */
memset(&entry->lock, 0, sizeof(entry->lock));
entry->r_owner = NULL;
entry->w_owner = NULL;
entry->r_fname = NULL;
entry->w_fname = NULL;
entry->r_lineno = 0;;
entry->w_lineno = 0;;
entry->r_lockcount = 0;;
entry->w_lockcount = 0;;
/* Initialise the read/write queues: */
_thread_queue_init(&entry->r_queue);
_thread_queue_init(&entry->w_queue);
/* Get the flags for the file: */
if (fd >= 3 && (entry->flags =
_thread_sys_fcntl(fd, F_GETFL, 0)) == -1) {
ret = -1;
}
else {
/* Check if a stdio descriptor: */
if (fd < 3)
/*
* Use the stdio flags read by
* _pthread_init() to avoid
* mistaking the non-blocking
* flag that, when set on one
* stdio fd, is set on all stdio
* fds.
*/
entry->flags = _pthread_stdio_flags[fd];
/*
* Make the file descriptor non-blocking.
* This might fail if the device driver does
* not support non-blocking calls, or if the
* driver is naturally non-blocking.
*/
saved_errno = errno;
_thread_sys_fcntl(fd, F_SETFL,
entry->flags | O_NONBLOCK);
errno = saved_errno;
/* Lock the file descriptor table: */
_SPINLOCK(&fd_table_lock);
/*
* Check if another thread allocated the
* file descriptor entry while this thread
* was doing the same thing. The table wasn't
* kept locked during this operation because
* it has the potential to recurse.
*/
if (_thread_fd_table[fd] == NULL) {
/* This thread wins: */
_thread_fd_table[fd] = entry;
entry = NULL;
}
/* Unlock the file descriptor table: */
_SPINUNLOCK(&fd_table_lock);
}
/*
* Check if another thread initialised the table entry
* before this one could:
*/
if (entry != NULL)
/*
* Throw away the table entry that this thread
* prepared. The other thread wins.
*/
free(entry);
}
/* Return the completion status: */
return (ret);
}
void
_thread_fd_unlock(int fd, int lock_type)
{
int ret;
/*
* Check that the file descriptor table is initialised for this
* entry:
*/
if ((ret = _thread_fd_table_init(fd)) == 0) {
/*
* Lock the file descriptor table entry to prevent
* other threads for clashing with the current
* thread's accesses:
*/
_SPINLOCK(&_thread_fd_table[fd]->lock);
/* Check if the running thread owns the read lock: */
if (_thread_fd_table[fd]->r_owner == _thread_run) {
/* Check the file descriptor and lock types: */
if (lock_type == FD_READ || lock_type == FD_RDWR) {
/*
* Decrement the read lock count for the
* running thread:
*/
_thread_fd_table[fd]->r_lockcount--;
/*
* Check if the running thread still has read
* locks on this file descriptor:
*/
if (_thread_fd_table[fd]->r_lockcount != 0) {
}
/*
* Get the next thread in the queue for a
* read lock on this file descriptor:
*/
else if ((_thread_fd_table[fd]->r_owner = _thread_queue_deq(&_thread_fd_table[fd]->r_queue)) == NULL) {
} else {
/*
* Set the state of the new owner of
* the thread to running:
*/
PTHREAD_NEW_STATE(_thread_fd_table[fd]->r_owner,PS_RUNNING);
/*
* Reset the number of read locks.
* This will be incremented by the
* new owner of the lock when it sees
* that it has the lock.
*/
_thread_fd_table[fd]->r_lockcount = 0;
}
}
}
/* Check if the running thread owns the write lock: */
if (_thread_fd_table[fd]->w_owner == _thread_run) {
/* Check the file descriptor and lock types: */
if (lock_type == FD_WRITE || lock_type == FD_RDWR) {
/*
* Decrement the write lock count for the
* running thread:
*/
_thread_fd_table[fd]->w_lockcount--;
/*
* Check if the running thread still has
* write locks on this file descriptor:
*/
if (_thread_fd_table[fd]->w_lockcount != 0) {
}
/*
* Get the next thread in the queue for a
* write lock on this file descriptor:
*/
else if ((_thread_fd_table[fd]->w_owner = _thread_queue_deq(&_thread_fd_table[fd]->w_queue)) == NULL) {
} else {
/*
* Set the state of the new owner of
* the thread to running:
*/
PTHREAD_NEW_STATE(_thread_fd_table[fd]->w_owner,PS_RUNNING);
/*
* Reset the number of write locks.
* This will be incremented by the
* new owner of the lock when it
* sees that it has the lock.
*/
_thread_fd_table[fd]->w_lockcount = 0;
}
}
}
/* Unlock the file descriptor table entry: */
_SPINUNLOCK(&_thread_fd_table[fd]->lock);
}
/* Nothing to return. */
return;
}
int
_thread_fd_lock(int fd, int lock_type, struct timespec * timeout)
{
int ret;
/*
* Check that the file descriptor table is initialised for this
* entry:
*/
if ((ret = _thread_fd_table_init(fd)) == 0) {
/*
* Lock the file descriptor table entry to prevent
* other threads for clashing with the current
* thread's accesses:
*/
_SPINLOCK(&_thread_fd_table[fd]->lock);
/* Check the file descriptor and lock types: */
if (lock_type == FD_READ || lock_type == FD_RDWR) {
/*
* Enter a loop to wait for the file descriptor to be
* locked for read for the current thread:
*/
while (_thread_fd_table[fd]->r_owner != _thread_run) {
/*
* Check if the file descriptor is locked by
* another thread:
*/
if (_thread_fd_table[fd]->r_owner != NULL) {
/*
* Another thread has locked the file
* descriptor for read, so join the
* queue of threads waiting for a
* read lock on this file descriptor:
*/
_thread_queue_enq(&_thread_fd_table[fd]->r_queue, _thread_run);
/*
* Save the file descriptor details
* in the thread structure for the
* running thread:
*/
_thread_run->data.fd.fd = fd;
/* Set the timeout: */
_thread_kern_set_timeout(timeout);
/*
* Unlock the file descriptor
* table entry:
*/
_SPINUNLOCK(&_thread_fd_table[fd]->lock);
/*
* Schedule this thread to wait on
* the read lock. It will only be
* woken when it becomes the next in
* the queue and is granted access
* to the lock by the thread
* that is unlocking the file
* descriptor.
*/
_thread_kern_sched_state(PS_FDLR_WAIT, __FILE__, __LINE__);
/*
* Lock the file descriptor
* table entry again:
*/
_SPINLOCK(&_thread_fd_table[fd]->lock);
} else {
/*
* The running thread now owns the
* read lock on this file descriptor:
*/
_thread_fd_table[fd]->r_owner = _thread_run;
/*
* Reset the number of read locks for
* this file descriptor:
*/
_thread_fd_table[fd]->r_lockcount = 0;
}
}
/* Increment the read lock count: */
_thread_fd_table[fd]->r_lockcount++;
}
/* Check the file descriptor and lock types: */
if (lock_type == FD_WRITE || lock_type == FD_RDWR) {
/*
* Enter a loop to wait for the file descriptor to be
* locked for write for the current thread:
*/
while (_thread_fd_table[fd]->w_owner != _thread_run) {
/*
* Check if the file descriptor is locked by
* another thread:
*/
if (_thread_fd_table[fd]->w_owner != NULL) {
/*
* Another thread has locked the file
* descriptor for write, so join the
* queue of threads waiting for a
* write lock on this file
* descriptor:
*/
_thread_queue_enq(&_thread_fd_table[fd]->w_queue, _thread_run);
/*
* Save the file descriptor details
* in the thread structure for the
* running thread:
*/
_thread_run->data.fd.fd = fd;
/* Set the timeout: */
_thread_kern_set_timeout(timeout);
/*
* Unlock the file descriptor
* table entry:
*/
_SPINUNLOCK(&_thread_fd_table[fd]->lock);
/*
* Schedule this thread to wait on
* the write lock. It will only be
* woken when it becomes the next in
* the queue and is granted access to
* the lock by the thread that is
* unlocking the file descriptor.
*/
_thread_kern_sched_state(PS_FDLW_WAIT, __FILE__, __LINE__);
/*
* Lock the file descriptor
* table entry again:
*/
_SPINLOCK(&_thread_fd_table[fd]->lock);
} else {
/*
* The running thread now owns the
* write lock on this file
* descriptor:
*/
_thread_fd_table[fd]->w_owner = _thread_run;
/*
* Reset the number of write locks
* for this file descriptor:
*/
_thread_fd_table[fd]->w_lockcount = 0;
}
}
/* Increment the write lock count: */
_thread_fd_table[fd]->w_lockcount++;
}
/* Unlock the file descriptor table entry: */
_SPINUNLOCK(&_thread_fd_table[fd]->lock);
}
/* Return the completion status: */
return (ret);
}
void
_thread_fd_unlock_debug(int fd, int lock_type, char *fname, int lineno)
{
int ret;
/*
* Check that the file descriptor table is initialised for this
* entry:
*/
if ((ret = _thread_fd_table_init(fd)) == 0) {
/*
* Lock the file descriptor table entry to prevent
* other threads for clashing with the current
* thread's accesses:
*/
_spinlock_debug(&_thread_fd_table[fd]->lock, fname, lineno);
/* Check if the running thread owns the read lock: */
if (_thread_fd_table[fd]->r_owner == _thread_run) {
/* Check the file descriptor and lock types: */
if (lock_type == FD_READ || lock_type == FD_RDWR) {
/*
* Decrement the read lock count for the
* running thread:
*/
_thread_fd_table[fd]->r_lockcount--;
/*
* Check if the running thread still has read
* locks on this file descriptor:
*/
if (_thread_fd_table[fd]->r_lockcount != 0) {
}
/*
* Get the next thread in the queue for a
* read lock on this file descriptor:
*/
else if ((_thread_fd_table[fd]->r_owner = _thread_queue_deq(&_thread_fd_table[fd]->r_queue)) == NULL) {
} else {
/*
* Set the state of the new owner of
* the thread to running:
*/
PTHREAD_NEW_STATE(_thread_fd_table[fd]->r_owner,PS_RUNNING);
/*
* Reset the number of read locks.
* This will be incremented by the
* new owner of the lock when it sees
* that it has the lock.
*/
_thread_fd_table[fd]->r_lockcount = 0;
}
}
}
/* Check if the running thread owns the write lock: */
if (_thread_fd_table[fd]->w_owner == _thread_run) {
/* Check the file descriptor and lock types: */
if (lock_type == FD_WRITE || lock_type == FD_RDWR) {
/*
* Decrement the write lock count for the
* running thread:
*/
_thread_fd_table[fd]->w_lockcount--;
/*
* Check if the running thread still has
* write locks on this file descriptor:
*/
if (_thread_fd_table[fd]->w_lockcount != 0) {
}
/*
* Get the next thread in the queue for a
* write lock on this file descriptor:
*/
else if ((_thread_fd_table[fd]->w_owner = _thread_queue_deq(&_thread_fd_table[fd]->w_queue)) == NULL) {
} else {
/*
* Set the state of the new owner of
* the thread to running:
*/
PTHREAD_NEW_STATE(_thread_fd_table[fd]->w_owner,PS_RUNNING);
/*
* Reset the number of write locks.
* This will be incremented by the
* new owner of the lock when it
* sees that it has the lock.
*/
_thread_fd_table[fd]->w_lockcount = 0;
}
}
}
/* Unlock the file descriptor table entry: */
_SPINUNLOCK(&_thread_fd_table[fd]->lock);
}
/* Nothing to return. */
return;
}
int
_thread_fd_lock_debug(int fd, int lock_type, struct timespec * timeout,
char *fname, int lineno)
{
int ret;
/*
* Check that the file descriptor table is initialised for this
* entry:
*/
if ((ret = _thread_fd_table_init(fd)) == 0) {
/*
* Lock the file descriptor table entry to prevent
* other threads for clashing with the current
* thread's accesses:
*/
_spinlock_debug(&_thread_fd_table[fd]->lock, fname, lineno);
/* Check the file descriptor and lock types: */
if (lock_type == FD_READ || lock_type == FD_RDWR) {
/*
* Enter a loop to wait for the file descriptor to be
* locked for read for the current thread:
*/
while (_thread_fd_table[fd]->r_owner != _thread_run) {
/*
* Check if the file descriptor is locked by
* another thread:
*/
if (_thread_fd_table[fd]->r_owner != NULL) {
/*
* Another thread has locked the file
* descriptor for read, so join the
* queue of threads waiting for a
* read lock on this file descriptor:
*/
_thread_queue_enq(&_thread_fd_table[fd]->r_queue, _thread_run);
/*
* Save the file descriptor details
* in the thread structure for the
* running thread:
*/
_thread_run->data.fd.fd = fd;
_thread_run->data.fd.branch = lineno;
_thread_run->data.fd.fname = fname;
/* Set the timeout: */
_thread_kern_set_timeout(timeout);
/*
* Unlock the file descriptor
* table entry:
*/
_SPINUNLOCK(&_thread_fd_table[fd]->lock);
/*
* Schedule this thread to wait on
* the read lock. It will only be
* woken when it becomes the next in
* the queue and is granted access
* to the lock by the thread
* that is unlocking the file
* descriptor.
*/
_thread_kern_sched_state(PS_FDLR_WAIT, __FILE__, __LINE__);
/*
* Lock the file descriptor
* table entry again:
*/
_SPINLOCK(&_thread_fd_table[fd]->lock);
} else {
/*
* The running thread now owns the
* read lock on this file descriptor:
*/
_thread_fd_table[fd]->r_owner = _thread_run;
/*
* Reset the number of read locks for
* this file descriptor:
*/
_thread_fd_table[fd]->r_lockcount = 0;
/*
* Save the source file details for
* debugging:
*/
_thread_fd_table[fd]->r_fname = fname;
_thread_fd_table[fd]->r_lineno = lineno;
}
}
/* Increment the read lock count: */
_thread_fd_table[fd]->r_lockcount++;
}
/* Check the file descriptor and lock types: */
if (lock_type == FD_WRITE || lock_type == FD_RDWR) {
/*
* Enter a loop to wait for the file descriptor to be
* locked for write for the current thread:
*/
while (_thread_fd_table[fd]->w_owner != _thread_run) {
/*
* Check if the file descriptor is locked by
* another thread:
*/
if (_thread_fd_table[fd]->w_owner != NULL) {
/*
* Another thread has locked the file
* descriptor for write, so join the
* queue of threads waiting for a
* write lock on this file
* descriptor:
*/
_thread_queue_enq(&_thread_fd_table[fd]->w_queue, _thread_run);
/*
* Save the file descriptor details
* in the thread structure for the
* running thread:
*/
_thread_run->data.fd.fd = fd;
_thread_run->data.fd.branch = lineno;
_thread_run->data.fd.fname = fname;
/* Set the timeout: */
_thread_kern_set_timeout(timeout);
/*
* Unlock the file descriptor
* table entry:
*/
_SPINUNLOCK(&_thread_fd_table[fd]->lock);
/*
* Schedule this thread to wait on
* the write lock. It will only be
* woken when it becomes the next in
* the queue and is granted access to
* the lock by the thread that is
* unlocking the file descriptor.
*/
_thread_kern_sched_state(PS_FDLW_WAIT, __FILE__, __LINE__);
/*
* Lock the file descriptor
* table entry again:
*/
_SPINLOCK(&_thread_fd_table[fd]->lock);
} else {
/*
* The running thread now owns the
* write lock on this file
* descriptor:
*/
_thread_fd_table[fd]->w_owner = _thread_run;
/*
* Reset the number of write locks
* for this file descriptor:
*/
_thread_fd_table[fd]->w_lockcount = 0;
/*
* Save the source file details for
* debugging:
*/
_thread_fd_table[fd]->w_fname = fname;
_thread_fd_table[fd]->w_lineno = lineno;
}
}
/* Increment the write lock count: */
_thread_fd_table[fd]->w_lockcount++;
}
/* Unlock the file descriptor table entry: */
_SPINUNLOCK(&_thread_fd_table[fd]->lock);
}
/* Return the completion status: */
return (ret);
}
#endif
Reference in New Issue View Git Blame Copy Permalink