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commit 5cc338565479a620244c2f8ff35956629c4dbf81
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Author: Florian Weimer <fweimer@redhat.com>
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Date: Fri Dec 10 05:14:24 2021 +0100
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nptl: Add one more barrier to nptl/tst-create1
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Without the bar_ctor_finish barrier, it was possible that thread2
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re-locked user_lock before ctor had a chance to lock it. ctor then
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blocked in its locking operation, xdlopen from the main thread
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did not return, and thread2 was stuck waiting in bar_dtor:
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thread 1: started.
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thread 2: started.
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thread 2: locked user_lock.
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constructor started: 0.
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thread 1: in ctor: started.
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thread 3: started.
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thread 3: done.
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thread 2: unlocked user_lock.
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thread 2: locked user_lock.
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Fixes the test in commit 83b5323261bb72313bffcf37476c1b8f0847c736
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("elf: Avoid deadlock between pthread_create and ctors [BZ #28357]").
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Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
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diff --git a/sysdeps/pthread/tst-create1.c b/sysdeps/pthread/tst-create1.c
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index 932586c30990d1d4..763ded8d7956f943 100644
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--- a/sysdeps/pthread/tst-create1.c
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+++ b/sysdeps/pthread/tst-create1.c
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@@ -33,6 +33,7 @@ thread 2: lock(user_lock) -> pthread_create
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*/
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static pthread_barrier_t bar_ctor;
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+static pthread_barrier_t bar_ctor_finish;
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static pthread_barrier_t bar_dtor;
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static pthread_mutex_t user_lock = PTHREAD_MUTEX_INITIALIZER;
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@@ -46,6 +47,7 @@ ctor (void)
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xpthread_mutex_unlock (&user_lock);
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dprintf (1, "thread 1: in ctor: unlocked user_lock.\n");
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dprintf (1, "thread 1: in ctor: done.\n");
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+ xpthread_barrier_wait (&bar_ctor_finish);
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}
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void
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@@ -81,6 +83,7 @@ thread2 (void *a)
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xpthread_mutex_unlock (&user_lock);
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dprintf (1, "thread 2: unlocked user_lock.\n");
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xpthread_join (t3);
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+ xpthread_barrier_wait (&bar_ctor_finish);
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xpthread_mutex_lock (&user_lock);
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dprintf (1, "thread 2: locked user_lock.\n");
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@@ -99,6 +102,7 @@ thread1 (void)
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{
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dprintf (1, "thread 1: started.\n");
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xpthread_barrier_init (&bar_ctor, NULL, 2);
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+ xpthread_barrier_init (&bar_ctor_finish, NULL, 2);
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xpthread_barrier_init (&bar_dtor, NULL, 2);
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pthread_t t2 = xpthread_create (0, thread2, 0);
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void *p = xdlopen ("tst-create1mod.so", RTLD_NOW | RTLD_GLOBAL);
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