From: Florian Weimer <fweimer@redhat.com>
To: libc-alpha@sourceware.org
Subject: [PATCH 2/3] nptl: pthread_kill, pthread_cancel should fail after exit (bug 19193)
Date: Tue, 17 Aug 2021 15:51:04 +0200 [thread overview]
Message-ID: <cae575bba7442ae16685b012cdca5d5e0d2d495c.1629208174.git.fweimer@redhat.com> (raw)
In-Reply-To: <cover.1629208174.git.fweimer@redhat.com>
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.
---
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
diff --git a/nptl/pthread_cancel.c b/nptl/pthread_cancel.c
index cc25ff21f3..9bac6e3b76 100644
--- a/nptl/pthread_cancel.c
+++ b/nptl/pthread_cancel.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)
diff --git a/nptl/pthread_kill.c b/nptl/pthread_kill.c
index f79a2b26fc..5d4c86f920 100644
--- a/nptl/pthread_kill.c
+++ b/nptl/pthread_kill.c
@@ -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;
}
diff --git a/sysdeps/pthread/Makefile b/sysdeps/pthread/Makefile
index 42f9fc5072..dedfa0d290 100644
--- a/sysdeps/pthread/Makefile
+++ b/sysdeps/pthread/Makefile
@@ -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 \
diff --git a/sysdeps/pthread/tst-pthread_cancel-exited.c b/sysdeps/pthread/tst-pthread_cancel-exited.c
new file mode 100644
index 0000000000..811c9bee07
--- /dev/null
+++ b/sysdeps/pthread/tst-pthread_cancel-exited.c
@@ -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>
diff --git a/sysdeps/pthread/tst-pthread_kill-exited.c b/sysdeps/pthread/tst-pthread_kill-exited.c
new file mode 100644
index 0000000000..7575fb6d58
--- /dev/null
+++ b/sysdeps/pthread/tst-pthread_kill-exited.c
@@ -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>
--
2.31.1
next prev parent reply other threads:[~2021-08-17 13:51 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-17 13:50 [PATCH 0/3] Fix ESRCH issues in pthread_cancel, pthread_kill Florian Weimer
2021-08-17 13:50 ` [PATCH 1/3] support: Add support_wait_for_thread_exit Florian Weimer
2021-08-19 16:12 ` Adhemerval Zanella
2021-08-19 16:22 ` Florian Weimer
2021-08-17 13:51 ` Florian Weimer [this message]
2021-08-17 13:51 ` [PATCH 3/3] nptl: Fix race between pthread_kill and thread exit (bug 12889) Florian Weimer
2021-08-19 16:12 ` Adhemerval Zanella
2021-08-19 16:37 ` Florian Weimer
2021-08-19 16:49 ` Adhemerval Zanella
2021-08-20 16:24 ` Florian Weimer
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