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| author | Martin Kuchta <martin.kuchta@netapp.com> | 2018-08-27 18:54:46 +0200 |
|---|---|---|
| committer | Florian Weimer <fweimer@redhat.com> | 2018-08-27 19:14:58 +0200 |
| commit | 174709d879a15590e00119c7f91dc2460aaf571c (patch) | |
| tree | ca4f58616dfe0300a0eb7b73f83973a2fc2ac319 | |
| parent | c9570bd2f54abb68e4e3c767aca3a54e05d2c7f6 (diff) | |
| download | glibc-174709d879a15590e00119c7f91dc2460aaf571c.tar.gz glibc-174709d879a15590e00119c7f91dc2460aaf571c.tar.xz glibc-174709d879a15590e00119c7f91dc2460aaf571c.zip | |
pthread_cond_broadcast: Fix waiters-after-spinning case [BZ #23538]
(cherry picked from commit 99ea93ca31795469d2a1f1570f17a5c39c2eb7e2)
| -rw-r--r-- | ChangeLog | 8 | ||||
| -rw-r--r-- | NEWS | 1 | ||||
| -rw-r--r-- | nptl/pthread_cond_common.c | 8 |
3 files changed, 15 insertions, 2 deletions
diff --git a/ChangeLog b/ChangeLog index 7e22bd1dfc..2b771ca994 100644 --- a/ChangeLog +++ b/ChangeLog @@ -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. + 2018-07-29 H.J. Lu <hongjiu.lu@intel.com> [BZ #23459] diff --git a/NEWS b/NEWS index 61ac02cd69..a868a652f7 100644 --- a/NEWS +++ b/NEWS @@ -146,6 +146,7 @@ The following bugs are resolved with this release: [23236] Harden function pointers in _IO_str_fields [23313] libio: Disable vtable validation in case of interposition [23349] Various glibc headers no longer compatible with <linux/time.h> + [23538] pthread_cond_broadcast: Fix waiters-after-spinning case [23363] stdio-common/tst-printf.c has non-free license [23456] Wrong index_cpu_LZCNT [23459] COMMON_CPUID_INDEX_80000001 isn't populated for Intel processors diff --git a/nptl/pthread_cond_common.c b/nptl/pthread_cond_common.c index ffbbde4106..c99435e439 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); |