commit 31e72bc3289acdd85b0b745fbf64c5949ca33432
author Jack Ren <jack.ren@intel.com> Mon Aug 01 18:44:55 2011 +0800
committer Jean-Baptiste Queru <jbq@google.com> Tue Nov 29 17:09:15 2011 -0800
tree e67e3743e9ceeeb8afdfe25121fbe62dc1608bce
parent 897815a1feff230be3ea42655a77dcbb9a8dcca9

bionic: fix __get_tls( ) crash issue

When running the stress test of pthread create/destroy, a crash may
oocur in __get_tls(). That is caused by the race condition with __set_tls( ):

Author: Jack Ren <jack.ren@intel.com>
Signed-off-by: Bruce Beare <bruce.j.beare@intel.com>

libc/arch-x86/bionic/__set_tls.c

diff --git a/libc/arch-x86/bionic/__set_tls.c b/libc/arch-x86/bionic/__set_tls.c
index 48b55f0..e5e43b5 100755
--- a/libc/arch-x86/bionic/__set_tls.c
+++ b/libc/arch-x86/bionic/__set_tls.c
@@ -60,6 +60,8 @@
     0
 };
 
+static pthread_mutex_t  _tls_desc_lock = PTHREAD_MUTEX_INITIALIZER;
+
 struct _thread_area_head {
     void *self;
 };
@@ -71,6 +73,7 @@
 {
     int   rc, segment;
 
+    pthread_mutex_lock(&_tls_desc_lock);
     _tls_desc.base_addr = (unsigned long)ptr;
 
     /* We also need to write the location of the tls to ptr[0] */
@@ -88,6 +91,8 @@
     asm __volatile__ (
         "   movw %w0, %%gs" :: "q"(segment)
     );
+    pthread_mutex_unlock(&_tls_desc_lock);
+
     return 0;
 }