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authorFlorian Weimer <fweimer@redhat.com>2019-02-08 12:46:19 +0100
committerFlorian Weimer <fweimer@redhat.com>2019-02-08 12:46:19 +0100
commit669ff911e2571f74a2668493e326ac9a505776bd (patch)
tree7cfe768081bfec3d9f9a10cbdd50364ed9ddb1fb /sysdeps/nptl/fork.c
parentd0bd87d4c0c11b93f79d1c3531ffb13b4b538190 (diff)
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nptl: Avoid fork handler lock for async-signal-safe fork [BZ #24161]
Commit 27761a1042daf01987e7d79636d0c41511c6df3c ("Refactor atfork handlers") introduced a lock, atfork_lock, around fork handler list accesses. It turns out that this lock occasionally results in self-deadlocks in malloc/tst-mallocfork2: (gdb) bt #0 __lll_lock_wait_private () at ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:63 #1 0x00007f160c6f927a in __run_fork_handlers (who=(unknown: 209394016), who@entry=atfork_run_prepare) at register-atfork.c:116 #2 0x00007f160c6b7897 in __libc_fork () at ../sysdeps/nptl/fork.c:58 #3 0x00000000004027d6 in sigusr1_handler (signo=<optimized out>) at tst-mallocfork2.c:80 #4 sigusr1_handler (signo=<optimized out>) at tst-mallocfork2.c:64 #5 <signal handler called> #6 0x00007f160c6f92e4 in __run_fork_handlers (who=who@entry=atfork_run_parent) at register-atfork.c:136 #7 0x00007f160c6b79a2 in __libc_fork () at ../sysdeps/nptl/fork.c:152 #8 0x0000000000402567 in do_test () at tst-mallocfork2.c:156 #9 0x0000000000402dd2 in support_test_main (argc=1, argv=0x7ffc81ef1ab0, config=config@entry=0x7ffc81ef1970) at support_test_main.c:350 #10 0x0000000000402362 in main (argc=<optimized out>, argv=<optimized out>) at ../support/test-driver.c:168 If no locking happens in the single-threaded case (where fork is expected to be async-signal-safe), this deadlock is avoided. (pthread_atfork is not required to be async-signal-safe, so a fork call from a signal handler interrupting pthread_atfork is not a problem.)
Diffstat (limited to 'sysdeps/nptl/fork.c')
-rw-r--r--sysdeps/nptl/fork.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/sysdeps/nptl/fork.c b/sysdeps/nptl/fork.c
index bd68f18b45..14b69a6f89 100644
--- a/sysdeps/nptl/fork.c
+++ b/sysdeps/nptl/fork.c
@@ -55,7 +55,7 @@ __libc_fork (void)
but our current fork implementation is not. */
bool multiple_threads = THREAD_GETMEM (THREAD_SELF, header.multiple_threads);
- __run_fork_handlers (atfork_run_prepare);
+ __run_fork_handlers (atfork_run_prepare, multiple_threads);
/* If we are not running multiple threads, we do not have to
preserve lock state. If fork runs from a signal handler, only
@@ -134,7 +134,7 @@ __libc_fork (void)
__rtld_lock_initialize (GL(dl_load_lock));
/* Run the handlers registered for the child. */
- __run_fork_handlers (atfork_run_child);
+ __run_fork_handlers (atfork_run_child, multiple_threads);
}
else
{
@@ -149,7 +149,7 @@ __libc_fork (void)
}
/* Run the handlers registered for the parent. */
- __run_fork_handlers (atfork_run_parent);
+ __run_fork_handlers (atfork_run_parent, multiple_threads);
}
return pid;