diff options
| author | Torvald Riegel <triegel@redhat.com> | 2015-04-28 23:24:36 +0200 |
|---|---|---|
| committer | Torvald Riegel <triegel@redhat.com> | 2015-06-04 15:34:30 +0200 |
| commit | b634486d57a14b53f1cfcf739e41ddf826e51977 (patch) | |
| tree | 65ad6788da14adc8effdd9d1b4236ac24af710d7 /nptl/pthread_rwlock_tryrdlock.c | |
| parent | 3c9c61febede148b79d8509e16588152d99b3774 (diff) | |
Fix missing wake-ups in pthread_rwlock_rdlock.
This adds wake-ups that would be missing if assuming that for a
non-writer-preferring rwlock, if one thread has acquired a rdlock and
does not release it, another thread will eventually acquire a rdlock too
despite concurrent write lock acquisition attempts. BZ 14958 is about
supporting this assumption. Strictly speaking, this isn't a valid
test case, but nonetheless worth supporting (see comment 7 of BZ 14958).
Diffstat (limited to 'nptl/pthread_rwlock_tryrdlock.c')
| -rw-r--r-- | nptl/pthread_rwlock_tryrdlock.c | 18 |
1 files changed, 17 insertions, 1 deletions
diff --git a/nptl/pthread_rwlock_tryrdlock.c b/nptl/pthread_rwlock_tryrdlock.c index d51d9aa930..cde123fd5d 100644 --- a/nptl/pthread_rwlock_tryrdlock.c +++ b/nptl/pthread_rwlock_tryrdlock.c @@ -20,12 +20,14 @@ #include "pthreadP.h" #include <lowlevellock.h> #include <elide.h> +#include <stdbool.h> int __pthread_rwlock_tryrdlock (pthread_rwlock_t *rwlock) { int result = EBUSY; + bool wake = false; if (ELIDE_TRYLOCK (rwlock->__data.__rwelision, rwlock->__data.__lock == 0 @@ -45,11 +47,25 @@ __pthread_rwlock_tryrdlock (pthread_rwlock_t *rwlock) result = EAGAIN; } else - result = 0; + { + result = 0; + /* See pthread_rwlock_rdlock. */ + if (rwlock->__data.__nr_readers == 1 + && rwlock->__data.__nr_readers_queued > 0 + && rwlock->__data.__nr_writers_queued > 0) + { + ++rwlock->__data.__readers_wakeup; + wake = true; + } + } } lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared); + if (wake) + lll_futex_wake (&rwlock->__data.__readers_wakeup, INT_MAX, + rwlock->__data.__shared); + return result; } strong_alias (__pthread_rwlock_tryrdlock, pthread_rwlock_tryrdlock) |