From 1324858a3fd3d0291f9dec45f771881ba7209150 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 6b5cfbab55..7349a33b11 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. + 2018-01-19 Tulio Magno Quites Machado Filho [BZ #22685] diff --git a/NEWS b/NEWS index dafec5d82d..abe90d1422 100644 --- a/NEWS +++ b/NEWS @@ -84,6 +84,7 @@ The following bugs are resolved with this release: [22685] powerpc: Fix syscalls during early process initialization [22715] x86-64: Properly align La_x86_64_retval to VEC_SIZE [22774] malloc: Integer overflow in malloc (CVE-2018-6551) + [23538] pthread_cond_broadcast: Fix waiters-after-spinning case Version 2.25 diff --git a/nptl/pthread_cond_common.c b/nptl/pthread_cond_common.c index 7c63ef9b89..886f0abcb3 100644 --- a/nptl/pthread_cond_common.c +++ b/nptl/pthread_cond_common.c @@ -406,8 +406,12 @@ __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 1.4.1