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| author | Martin Kuchta <martin.kuchta@netapp.com> | 2018-08-27 17:03:35 +0200 |
|---|---|---|
| committer | Florian Weimer <fweimer@redhat.com> | 2018-08-27 17:03:35 +0200 |
| commit | 99ea93ca31795469d2a1f1570f17a5c39c2eb7e2 (patch) | |
| tree | 3a2888b3caad0299c4c4137ccf9b5f5f035d2b37 | |
| parent | 4061791fccec50dfcd13b72ccb926dedc58b9680 (diff) | |
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pthread_cond_broadcast: Fix waiters-after-spinning case [BZ #23538]
| -rw-r--r-- | ChangeLog | 8 | ||||
| -rw-r--r-- | nptl/pthread_cond_common.c | 8 |
2 files changed, 14 insertions, 2 deletions
@@ -1,3 +1,11 @@ +2018-08-27 Martin Kuchta <martin.kuchta@netapp.com> + Torvald Riegel <triegel@redhat.com> + + [BZ #23538] + * nptl/pthread_cond_common.c (__condvar_quiesce_and_switch_g1): + Update r to include the set wake-request flag if waiters are + remaining after spinning. + 2018-08-27 Joseph Myers <joseph@codesourcery.com> * sysdeps/gnu/netinet/udp.h (UDP_SEGMENT): New macro. diff --git a/nptl/pthread_cond_common.c b/nptl/pthread_cond_common.c index 8e425eb01e..479e54febb 100644 --- a/nptl/pthread_cond_common.c +++ b/nptl/pthread_cond_common.c @@ -405,8 +405,12 @@ __condvar_quiesce_and_switch_g1 (pthread_cond_t *cond, uint64_t wseq, { /* There is still a waiter after spinning. Set the wake-request flag and block. Relaxed MO is fine because this is just about - this futex word. */ - r = atomic_fetch_or_relaxed (cond->__data.__g_refs + g1, 1); + this futex word. + + Update r to include the set wake-request flag so that the upcoming + futex_wait only blocks if the flag is still set (otherwise, we'd + violate the basic client-side futex protocol). */ + r = atomic_fetch_or_relaxed (cond->__data.__g_refs + g1, 1) | 1; if ((r >> 1) > 0) futex_wait_simple (cond->__data.__g_refs + g1, r, private); |