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pthread_cond_broadcast: Fix waiters-after-spinning case [BZ #23538] 

(cherry picked from commit 99ea93ca31)
This commit is contained in:
Martin Kuchta 2018-08-27 18:54:46 +02:00 committed by Florian Weimer
parent c87b5bab24
commit aa8a3e4cde
3 changed files with 15 additions and 2 deletions
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8
ChangeLog
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@ -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.
2018-08-03 DJ Delorie <dj@redhat.com>
* sysdeps/riscv/rvf/math_private.h (libc_feholdexcept_setround_riscv):

1
NEWS
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@ -11,6 +11,7 @@ The following bugs are resolved with this release:
[23497] readdir64@GLIBC_2.1 cannot parse the kernel directory stream
[23521] nss_files aliases database file stream leak
[23538] pthread_cond_broadcast: Fix waiters-after-spinning case
Version 2.28

8
nptl/pthread_cond_common.c
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@ -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);