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_timedrdlock.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_timedrdlock.c')
| -rw-r--r-- | nptl/pthread_rwlock_timedrdlock.c | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/nptl/pthread_rwlock_timedrdlock.c b/nptl/pthread_rwlock_timedrdlock.c index 0212b49adb..63fb313762 100644 --- a/nptl/pthread_rwlock_timedrdlock.c +++ b/nptl/pthread_rwlock_timedrdlock.c @@ -23,6 +23,7 @@ #include <pthreadP.h> #include <sys/time.h> #include <kernel-features.h> +#include <stdbool.h> /* Try to acquire read lock for RWLOCK or return after specfied time. */ @@ -32,6 +33,7 @@ pthread_rwlock_timedrdlock (rwlock, abstime) const struct timespec *abstime; { int result = 0; + bool wake = false; /* Make sure we are alone. */ lll_lock(rwlock->__data.__lock, rwlock->__data.__shared); @@ -53,6 +55,17 @@ pthread_rwlock_timedrdlock (rwlock, abstime) --rwlock->__data.__nr_readers; result = EAGAIN; } + else + { + /* 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; + } + } break; } @@ -153,5 +166,9 @@ pthread_rwlock_timedrdlock (rwlock, abstime) /* We are done, free the lock. */ lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared); + if (wake) + lll_futex_wake (&rwlock->__data.__readers_wakeup, INT_MAX, + rwlock->__data.__shared); + return result; } |