traverseda
/
cpython
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

[2.7] bpo-30765: Avoid blocking when PyThread_acquire_lock() is asked not to (GH-2403) (#2420) 

* [2.7] bpo-30765: Avoid blocking when PyThread_acquire_lock() is asked not to (GH-2403)

* bpo-30765: Avoid blocking when PyThread_acquire_lock() is asked not to lock

This is especially important if PyThread_acquire_lock() is called reentrantly
(for example from a signal handler).

* Update 2017-06-26-14-29-50.bpo-30765.Q5iBmf.rst

* Avoid core logic when taking the mutex failed.
(cherry picked from commit f84ac420c2)

* Remove test undef
This commit is contained in:
Antoine Pitrou 2017-06-26 22:13:39 +02:00 committed by GitHub
parent 787826c931
commit 828488393c
2 changed files with 31 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
Misc/NEWS.d/next/Core and Builtins/2017-06-26-14-29-50.bpo-30765.Q5iBmf.rst Normal file
View File

@ -0,0 +1,2 @@
Avoid blocking in pthread_mutex_lock() when PyThread_acquire_lock() is asked
not to block.

48
Python/thread_pthread.h
View File

@ -410,31 +410,41 @@ PyThread_free_lock(PyThread_type_lock lock)
int
PyThread_acquire_lock(PyThread_type_lock lock, int waitflag)
{
int success;
int success = 0;
pthread_lock *thelock = (pthread_lock *)lock;
int status, error = 0;
dprintf(("PyThread_acquire_lock(%p, %d) called\n", lock, waitflag));
status = pthread_mutex_lock( &thelock->mut );
CHECK_STATUS("pthread_mutex_lock[1]");
success = thelock->locked == 0;
if ( !success && waitflag ) {
/* continue trying until we get the lock */
/* mut must be locked by me -- part of the condition
* protocol */
while ( thelock->locked ) {
status = pthread_cond_wait(&thelock->lock_released,
&thelock->mut);
CHECK_STATUS("pthread_cond_wait");
}
success = 1;
if (waitflag) {
status = pthread_mutex_lock( &thelock->mut );
CHECK_STATUS("pthread_mutex_lock[1]");
}
else {
status = pthread_mutex_trylock( &thelock->mut );
if (status != EBUSY)
CHECK_STATUS("pthread_mutex_trylock[1]");
}
if (status == 0) {
success = thelock->locked == 0;
if ( !success && waitflag ) {
/* continue trying until we get the lock */
/* mut must be locked by me -- part of the condition
* protocol */
while ( thelock->locked ) {
status = pthread_cond_wait(&thelock->lock_released,
&thelock->mut);
CHECK_STATUS("pthread_cond_wait");
}
success = 1;
}
if (success) thelock->locked = 1;
status = pthread_mutex_unlock( &thelock->mut );
CHECK_STATUS("pthread_mutex_unlock[1]");
}
if (success) thelock->locked = 1;
status = pthread_mutex_unlock( &thelock->mut );
CHECK_STATUS("pthread_mutex_unlock[1]");
if (error) success = 0;
dprintf(("PyThread_acquire_lock(%p, %d) -> %d\n", lock, waitflag, success));