From aa8a3e4cdef20c50cb20f008864fff05cbfbdf29 Mon Sep 17 00:00:00 2001 From: Martin Kuchta Date: Mon, 27 Aug 2018 18:54:46 +0200 Subject: pthread_cond_broadcast: Fix waiters-after-spinning case [BZ #23538] (cherry picked from commit 99ea93ca31795469d2a1f1570f17a5c39c2eb7e2) --- ChangeLog | 8 ++++++++ NEWS | 1 + nptl/pthread_cond_common.c | 8 ++++++-- 3 files changed, 15 insertions(+), 2 deletions(-) diff --git a/ChangeLog b/ChangeLog index b9e732a192..ef83777833 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,11 @@ +2018-08-27 Martin Kuchta + Torvald Riegel + + [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 * sysdeps/riscv/rvf/math_private.h (libc_feholdexcept_setround_riscv): diff --git a/NEWS b/NEWS index 873cf8f64f..3073712cba 100644 --- a/NEWS +++ b/NEWS @@ -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 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); -- cgit v1.2.1