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authorAdhemerval Zanella <adhemerval.zanella@linaro.org>2022-06-07 11:11:03 -0300
committerAdhemerval Zanella <adhemerval.zanella@linaro.org>2022-06-24 17:45:58 -0300
commitbaf2a265c71113a91f6971313ef191be9e77ef6a (patch)
treead894e8766707e8c10e98b6e4c857ab315fa0276 /nptl
parent5b41b2659d35b72636ab50a28d6815cad9c22a66 (diff)
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misc: Optimize internal usage of __libc_single_threaded
By adding an internal alias to avoid the GOT indirection.
On some architecture, __libc_single_thread may be accessed through
copy relocations and thus it requires to update also the copies
default copy.

This is done by adding a new internal macro,
libc_hidden_data_{proto,def}, which has an addition argument that
specifies the alias name (instead of default __GI_ one).

Checked on x86_64-linux-gnu and i686-linux-gnu.

Reviewed-by: Fangrui Song <maskray@google.com>
Diffstat (limited to 'nptl')
-rw-r--r--nptl/pthread_create.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/nptl/pthread_create.c b/nptl/pthread_create.c
index e7a099acb7..a06d611e32 100644
--- a/nptl/pthread_create.c
+++ b/nptl/pthread_create.c
@@ -624,9 +624,12 @@ __pthread_create_2_1 (pthread_t *newthread, const pthread_attr_t *attr,
 
   /* Avoid a data race in the multi-threaded case, and call the
      deferred initialization only once.  */
-  if (__libc_single_threaded)
+  if (__libc_single_threaded_internal)
     {
       late_init ();
+      __libc_single_threaded_internal = 0;
+      /* __libc_single_threaded can be accessed through copy relocations, so
+	 it requires to update the external copy.  */
       __libc_single_threaded = 0;
     }