[v2,2/4] nptl: pthread_kill, pthread_cancel should fail after exit (bug 19193)
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dj/TryBot-apply_patch |
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Patch applied to master at the time it was sent
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Commit Message
This closes one remaining race condition related to bug 12889: if
the thread already exited on the kernel side, returning ESRCH
is not correct because that error is reserved for the thread IDs
(pthread_t values) whose lifetime has ended. In case of a
kernel-side exit and a valid thread ID, no signal needs to be sent
and cancellation does not have an effect, so just return 0.
sysdeps/pthread/tst-kill4.c triggers undefined behavior and is
removed with this commit.
---
v2: Actually unchanged.
nptl/pthread_cancel.c | 9 ++--
nptl/pthread_kill.c | 7 +++-
sysdeps/pthread/Makefile | 5 ++-
sysdeps/pthread/tst-pthread_cancel-exited.c | 45 ++++++++++++++++++++
sysdeps/pthread/tst-pthread_kill-exited.c | 46 +++++++++++++++++++++
5 files changed, 106 insertions(+), 6 deletions(-)
create mode 100644 sysdeps/pthread/tst-pthread_cancel-exited.c
create mode 100644 sysdeps/pthread/tst-pthread_kill-exited.c
@@ -62,10 +62,11 @@ __pthread_cancel (pthread_t th)
{
volatile struct pthread *pd = (volatile struct pthread *) th;
- /* Make sure the descriptor is valid. */
- if (INVALID_TD_P (pd))
- /* Not a valid thread handle. */
- return ESRCH;
+ if (pd->tid == 0)
+ /* The thread has already exited on the kernel side. Its outcome
+ (regular exit, other cancelation) has already been
+ determined. */
+ return 0;
static int init_sigcancel = 0;
if (atomic_load_relaxed (&init_sigcancel) == 0)
@@ -46,7 +46,12 @@ __pthread_kill_internal (pthread_t threadid, int signo)
? INTERNAL_SYSCALL_ERRNO (val) : 0);
}
else
- val = ESRCH;
+ /* The kernel reports that the thread has exited. POSIX specifies
+ the ESRCH error only for the case when the lifetime of a thread
+ ID has ended, but calling pthread_kill on such a thread ID is
+ undefined in glibc. Therefore, do not treat kernel thread exit
+ as an error. */
+ val = 0;
return val;
}
@@ -89,7 +89,7 @@ tests += tst-cnd-basic tst-mtx-trylock tst-cnd-broadcast \
tst-join8 tst-join9 tst-join10 tst-join11 tst-join12 tst-join13 \
tst-join14 tst-join15 \
tst-key1 tst-key2 tst-key3 tst-key4 \
- tst-kill1 tst-kill2 tst-kill3 tst-kill4 tst-kill5 tst-kill6 \
+ tst-kill1 tst-kill2 tst-kill3 tst-kill5 tst-kill6 \
tst-locale1 tst-locale2 \
tst-memstream \
tst-mutex-errorcheck tst-mutex1 tst-mutex2 tst-mutex3 tst-mutex4 \
@@ -118,6 +118,9 @@ tests += tst-cnd-basic tst-mtx-trylock tst-cnd-broadcast \
tst-unload \
tst-unwind-thread \
tst-pt-vfork1 tst-pt-vfork2 tst-vfork1x tst-vfork2x \
+ tst-pthread_cancel-exited \
+ tst-pthread_kill-exited \
+ # tests
tests-time64 := \
tst-abstime-time64 \
new file mode 100644
@@ -0,0 +1,45 @@
+/* Test that pthread_kill succeeds for an exited thread.
+ Copyright (C) 2021 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+/* This test verifies that pthread_kill returns 0 (and not ESRCH) for
+ a thread that has exited on the kernel side. */
+
+#include <stddef.h>
+#include <support/support.h>
+#include <support/xthread.h>
+
+static void *
+noop_thread (void *closure)
+{
+ return NULL;
+}
+
+static int
+do_test (void)
+{
+ pthread_t thr = xpthread_create (NULL, noop_thread, NULL);
+
+ support_wait_for_thread_exit ();
+
+ xpthread_cancel (thr);
+ xpthread_join (thr);
+
+ return 0;
+}
+
+#include <support/test-driver.c>
new file mode 100644
@@ -0,0 +1,46 @@
+/* Test that pthread_kill succeeds for an exited thread.
+ Copyright (C) 2021 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+/* This test verifies that pthread_kill returns 0 (and not ESRCH) for
+ a thread that has exited on the kernel side. */
+
+#include <signal.h>
+#include <stddef.h>
+#include <support/support.h>
+#include <support/xthread.h>
+
+static void *
+noop_thread (void *closure)
+{
+ return NULL;
+}
+
+static int
+do_test (void)
+{
+ pthread_t thr = xpthread_create (NULL, noop_thread, NULL);
+
+ support_wait_for_thread_exit ();
+
+ xpthread_kill (thr, SIGUSR1);
+ xpthread_join (thr);
+
+ return 0;
+}
+
+#include <support/test-driver.c>