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[Qemu-devel] [PULL 02/46] qemu-thread: fix races on threads that exit ve
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PULL 02/46] qemu-thread: fix races on threads that exit very quickly |
Date: |
Wed, 20 Dec 2017 18:14:14 +0100 |
From: linzhecheng <address@hidden>
If we create a thread with QEMU_THREAD_DETACHED mode, QEMU may get a segfault
with low probability.
The backtrace is:
#0 0x00007f46c60291d7 in __GI_raise (address@hidden) at
../nptl/sysdeps/unix/sysv/linux/raise.c:56
#1 0x00007f46c602a8c8 in __GI_abort () at abort.c:90
#2 0x00000000008543c9 in PAT_abort ()
#3 0x000000000085140d in patchIllInsHandler ()
#4 <signal handler called>
#5 pthread_detach (th=139933037614848) at pthread_detach.c:50
#6 0x0000000000829759 in qemu_thread_create (address@hidden, address@hidden
"io-task-worker", address@hidden <qio_task_thread_worker>,
address@hidden, address@hidden) at util/qemu_thread_posix.c:512
#7 0x00000000007ebc96 in qio_task_run_in_thread (task=0x31db2c0,
address@hidden <qio_channel_socket_connect_worker>, opaque=0xcd23380,
destroy=0x7f1180 <qapi_free_SocketAddress>)
at io/task.c:141
#8 0x00000000007e7f33 in qio_channel_socket_connect_async (address@hidden,
addr=<optimized out>, address@hidden <qemu_chr_socket_connected>,
address@hidden,
address@hidden) at io/channel_socket.c:194
#9 0x000000000055bdd1 in socket_reconnect_timeout (opaque=0x42862c0) at
qemu_char.c:4744
#10 0x00007f46c72483b3 in g_timeout_dispatch () from
/usr/lib64/libglib-2.0.so.0
#11 0x00007f46c724799a in g_main_context_dispatch () from
/usr/lib64/libglib-2.0.so.0
#12 0x000000000076c646 in glib_pollfds_poll () at main_loop.c:228
#13 0x000000000076c6eb in os_host_main_loop_wait (timeout=348000000) at
main_loop.c:273
#14 0x000000000076c815 in main_loop_wait (address@hidden) at main_loop.c:521
#15 0x000000000056a511 in main_loop () at vl.c:2076
#16 0x0000000000420705 in main (argc=<optimized out>, argv=<optimized out>,
envp=<optimized out>) at vl.c:4940
The cause of this problem is a glibc bug; for more information, see
https://sourceware.org/bugzilla/show_bug.cgi?id=19951.
The solution for this bug is to use pthread_attr_setdetachstate.
There is a similar issue with pthread_setname_np, which is moved
from creating thread to created thread.
Signed-off-by: linzhecheng <address@hidden>
Message-Id: <address@hidden>
Reviewed-by: Fam Zheng <address@hidden>
[Simplify the code by removing qemu_thread_set_name, and free the arguments
before invoking the start routine. - Paolo]
Signed-off-by: Paolo Bonzini <address@hidden>
---
util/qemu-thread-posix.c | 59 ++++++++++++++++++++++++++++++++++--------------
1 file changed, 42 insertions(+), 17 deletions(-)
diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
index 7306475..fcd369b 100644
--- a/util/qemu-thread-posix.c
+++ b/util/qemu-thread-posix.c
@@ -479,15 +479,29 @@ static void __attribute__((constructor))
qemu_thread_atexit_init(void)
}
-/* Attempt to set the threads name; note that this is for debug, so
- * we're not going to fail if we can't set it.
- */
-static void qemu_thread_set_name(QemuThread *thread, const char *name)
-{
#ifdef CONFIG_PTHREAD_SETNAME_NP
- pthread_setname_np(thread->thread, name);
-#endif
+typedef struct {
+ void *(*start_routine)(void *);
+ void *arg;
+ char *name;
+} QemuThreadArgs;
+
+static void *qemu_thread_start(void *args)
+{
+ QemuThreadArgs *qemu_thread_args = args;
+ void *(*start_routine)(void *) = qemu_thread_args->start_routine;
+ void *arg = qemu_thread_args->arg;
+
+ /* Attempt to set the threads name; note that this is for debug, so
+ * we're not going to fail if we can't set it.
+ */
+ pthread_setname_np(pthread_self(), qemu_thread_args->name);
+ g_free(qemu_thread_args->name);
+ g_free(qemu_thread_args);
+ return start_routine(arg);
}
+#endif
+
void qemu_thread_create(QemuThread *thread, const char *name,
void *(*start_routine)(void*),
@@ -496,29 +510,40 @@ void qemu_thread_create(QemuThread *thread, const char
*name,
sigset_t set, oldset;
int err;
pthread_attr_t attr;
+ QemuThreadArgs *qemu_thread_args;
err = pthread_attr_init(&attr);
if (err) {
error_exit(err, __func__);
}
+ if (mode == QEMU_THREAD_DETACHED) {
+ pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
+ }
+
/* Leave signal handling to the iothread. */
sigfillset(&set);
pthread_sigmask(SIG_SETMASK, &set, &oldset);
- err = pthread_create(&thread->thread, &attr, start_routine, arg);
- if (err)
- error_exit(err, __func__);
+#ifdef CONFIG_PTHREAD_SETNAME_NP
if (name_threads) {
- qemu_thread_set_name(thread, name);
+ qemu_thread_args = g_new0(QemuThreadArgs, 1);
+ qemu_thread_args->name = g_strdup(name);
+ qemu_thread_args->start_routine = start_routine;
+ qemu_thread_args->arg = arg;
+
+ err = pthread_create(&thread->thread, &attr,
+ qemu_thread_start, qemu_thread_args);
+ } else
+#endif
+ {
+ err = pthread_create(&thread->thread, &attr,
+ start_routine, arg);
}
- if (mode == QEMU_THREAD_DETACHED) {
- err = pthread_detach(thread->thread);
- if (err) {
- error_exit(err, __func__);
- }
- }
+ if (err)
+ error_exit(err, __func__);
+
pthread_sigmask(SIG_SETMASK, &oldset, NULL);
pthread_attr_destroy(&attr);
--
1.8.3.1
- [Qemu-devel] [PULL 00/46] First batch of misc patches for QEMU 2.12, Paolo Bonzini, 2017/12/20
- [Qemu-devel] [PULL 01/46] memfd: fix configure test, Paolo Bonzini, 2017/12/20
- [Qemu-devel] [PULL 02/46] qemu-thread: fix races on threads that exit very quickly,
Paolo Bonzini <=
- [Qemu-devel] [PULL 03/46] qemu-pr-helper: miscellaneous fixes, Paolo Bonzini, 2017/12/20
- [Qemu-devel] [PULL 04/46] contrib: add systemd unit files, Paolo Bonzini, 2017/12/20
- [Qemu-devel] [PULL 06/46] scsi-block: Add share-rw option, Paolo Bonzini, 2017/12/20
- [Qemu-devel] [PULL 05/46] Revert "docker: Enable features explicitly in test-full", Paolo Bonzini, 2017/12/20
- [Qemu-devel] [PULL 07/46] MAITAINERS: List Fam Zheng as reviewer for SCSI patches, Paolo Bonzini, 2017/12/20
- [Qemu-devel] [PULL 09/46] hyperv: set partition-wide MSRs only on first vcpu, Paolo Bonzini, 2017/12/20
- [Qemu-devel] [PULL 10/46] hyperv: ensure SINTx msrs are reset properly, Paolo Bonzini, 2017/12/20
- [Qemu-devel] [PULL 08/46] x86/cpu: Enable new SSE/AVX/AVX512 cpu features, Paolo Bonzini, 2017/12/20
- [Qemu-devel] [PULL 12/46] cpus: make pause_all_cpus() play with SMP on single threaded TCG, Paolo Bonzini, 2017/12/20
- [Qemu-devel] [PULL 13/46] cpu-exec: fix missed CPU kick during interrupt injection, Paolo Bonzini, 2017/12/20