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From: Florian Weimer <fw@sourceware.org> To: glibc-cvs@sourceware.org Subject: [glibc/release/2.34/master] nptl: Add one more barrier to nptl/tst-create1 Date: Fri, 10 Dec 2021 10:56:39 +0000 (GMT) [thread overview] Message-ID: <20211210105639.5DEC63858D35@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=e9f81c261a2ca74d31d07ff9c8e780ac8a25993c commit e9f81c261a2ca74d31d07ff9c8e780ac8a25993c Author: Florian Weimer <fweimer@redhat.com> Date: Fri Dec 10 05:14:24 2021 +0100 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> (cherry picked from commit 5cc338565479a620244c2f8ff35956629c4dbf81) Diff: --- NEWS | 1 + sysdeps/pthread/tst-create1.c | 4 ++++ 2 files changed, 5 insertions(+) diff --git a/NEWS b/NEWS index 8c68273929..698964bb9e 100644 --- a/NEWS +++ b/NEWS @@ -21,6 +21,7 @@ The following bugs are resolved with this release: [28524] Conversion from ISO-2022-JP-3 with iconv may emit spurious NULs [28607] Masked signals are delivered on thread exit [28532] powerpc64[le]: CFI for assembly templated syscalls is incorrect + [28678] nptl/tst-create1 hangs sporadically \f Version 2.34 diff --git a/sysdeps/pthread/tst-create1.c b/sysdeps/pthread/tst-create1.c index 932586c309..763ded8d79 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);
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