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stdlib: resolve a double lock init issue after fork [BZ #32994] 

The __abort_fork_reset_child (introduced in
d40ac01cbb) call resets the lock after the
fork. This causes a DRD regression in valgrind
(https://bugs.kde.org/show_bug.cgi?id=503668), as it's effectively a
double initialization, despite it being actually ok in this case. As
suggested in https://sourceware.org/bugzilla/show_bug.cgi?id=32994#c2
we replace it here with a memcpy of another initialized lock instead,
which makes valgrind happy.

Reviewed-by: Florian Weimer <fweimer@redhat.com>
This commit is contained in:
Davide Cavalca 2025-07-31 17:32:58 +02:00 committed by Florian Weimer
parent 258126bc0b
commit d9a348d092
1 changed files with 5 additions and 1 deletions
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6
stdlib/abort.c
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@ -19,6 +19,7 @@
#include <internal-signals.h> #include <internal-signals.h>
#include <libc-lock.h> #include <libc-lock.h>
#include <pthreadP.h> #include <pthreadP.h>
#include <string.h>
#include <unistd.h> #include <unistd.h>
/* Try to get a machine dependent instruction which will make the /* Try to get a machine dependent instruction which will make the
@ -42,7 +43,10 @@ __libc_rwlock_define_initialized (static, lock);
void void
__abort_fork_reset_child (void) __abort_fork_reset_child (void)
{ {
__libc_rwlock_init (lock); /* Reinitialize lock without calling pthread_rwlock_init, to
avoid a valgrind DRD false positive. */
__libc_rwlock_define_initialized (, reset_lock);
memcpy (&lock, &reset_lock, sizeof (lock));
} }
void void