lib/glibc
1
0
Fork 0
mirror of https://sourceware.org/git/glibc.git synced 2025-07-30 22:43:12 +03:00
Code Activity

Fix rwlock stall with PREFER_WRITER_NONRECURSIVE_NP (bug 23861)

Browse Source 
In the read lock function (__pthread_rwlock_rdlock_full) there was a
code path which would fail to reload __readers while waiting for
PTHREAD_RWLOCK_RWAITING to change. This failure to reload __readers
into a local value meant that various conditionals used the old value
of __readers and with only two threads left it could result in an
indefinite stall of one of the readers (waiting for PTHREAD_RWLOCK_RWAITING
to go to zero, but it never would).
This commit is contained in:
Andreas Schwab
2018-11-08 14:28:22 +01:00
parent 3d265911c2
commit f21e8f8ca4
4 changed files with 95 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
nptl/pthread_rwlock_common.c
View File

@ -314,7 +314,7 @@ __pthread_rwlock_rdlock_full (pthread_rwlock_t *rwlock,
harmless because the flag is just about the state of
__readers, and all threads set the flag under the same
conditions. */
while ((atomic_load_relaxed (&rwlock->__data.__readers)
while (((r = atomic_load_relaxed (&rwlock->__data.__readers))
& PTHREAD_RWLOCK_RWAITING) != 0)
{
int private = __pthread_rwlock_get_private (rwlock);