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From 5cc338565479a620244c2f8ff35956629c4dbf81 Mon Sep 17 00:00:00 2001
From: Florian Weimer <fweimer@redhat.com>
Date: Fri, 10 Dec 2021 05:14:24 +0100
Subject: [PATCH] nptl: Add one more barrier to nptl/tst-create1
Without the bar_ctor_finish barrier, it was possible that thread2
re-locked user_lock before ctor had a chance to lock it. ctor then
blocked in its locking operation, xdlopen from the main thread
did not return, and thread2 was stuck waiting in bar_dtor:
thread 1: started.
thread 2: started.
thread 2: locked user_lock.
constructor started: 0.
thread 1: in ctor: started.
thread 3: started.
thread 3: done.
thread 2: unlocked user_lock.
thread 2: locked user_lock.
Fixes the test in commit 83b5323261bb72313bffcf37476c1b8f0847c736
("elf: Avoid deadlock between pthread_create and ctors [BZ #28357]").
Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
---
sysdeps/pthread/tst-create1.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/sysdeps/pthread/tst-create1.c b/sysdeps/pthread/tst-create1.c
index 932586c..763ded8 100644
--- a/sysdeps/pthread/tst-create1.c
+++ b/sysdeps/pthread/tst-create1.c
@@ -33,6 +33,7 @@ thread 2: lock(user_lock) -> pthread_create
*/
static pthread_barrier_t bar_ctor;
+static pthread_barrier_t bar_ctor_finish;
static pthread_barrier_t bar_dtor;
static pthread_mutex_t user_lock = PTHREAD_MUTEX_INITIALIZER;
@@ -46,6 +47,7 @@ ctor (void)
xpthread_mutex_unlock (&user_lock);
dprintf (1, "thread 1: in ctor: unlocked user_lock.\n");
dprintf (1, "thread 1: in ctor: done.\n");
+ xpthread_barrier_wait (&bar_ctor_finish);
}
void
@@ -81,6 +83,7 @@ thread2 (void *a)
xpthread_mutex_unlock (&user_lock);
dprintf (1, "thread 2: unlocked user_lock.\n");
xpthread_join (t3);
+ xpthread_barrier_wait (&bar_ctor_finish);
xpthread_mutex_lock (&user_lock);
dprintf (1, "thread 2: locked user_lock.\n");
@@ -99,6 +102,7 @@ thread1 (void)
{
dprintf (1, "thread 1: started.\n");
xpthread_barrier_init (&bar_ctor, NULL, 2);
+ xpthread_barrier_init (&bar_ctor_finish, NULL, 2);
xpthread_barrier_init (&bar_dtor, NULL, 2);
pthread_t t2 = xpthread_create (0, thread2, 0);
void *p = xdlopen ("tst-create1mod.so", RTLD_NOW | RTLD_GLOBAL);
--
1.8.3.1
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