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GNU C Library master sources branch release/2.25/master updated. glibc-2.25-128-g1324858


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      from  71616d59ec97fe798b69f749e7fb424bd6d2432b (commit)

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- Log -----------------------------------------------------------------
http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=1324858a3fd3d0291f9dec45f771881ba7209150

commit 1324858a3fd3d0291f9dec45f771881ba7209150
Author: Martin Kuchta <martin.kuchta@netapp.com>
Date:   Mon Aug 27 18:54:46 2018 +0200

    pthread_cond_broadcast: Fix waiters-after-spinning case [BZ #23538]
    
    (cherry picked from commit 99ea93ca31795469d2a1f1570f17a5c39c2eb7e2)

diff --git a/ChangeLog b/ChangeLog
index 6b5cfba..7349a33 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.
+
 2018-01-19  Tulio Magno Quites Machado Filho  <tuliom@linux.vnet.ibm.com>
 
 	[BZ #22685]
diff --git a/NEWS b/NEWS
index dafec5d..abe90d1 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 7c63ef9..886f0ab 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);

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog                  |    8 ++++++++
 NEWS                       |    1 +
 nptl/pthread_cond_common.c |    8 ++++++--
 3 files changed, 15 insertions(+), 2 deletions(-)


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