[Resend] The QEMU crashes since invoking qemu_thread_set_name(), the backtrace is:

Commit Message

Zhanghailiang Dec. 28, 2016, 3:34 a.m. UTC

From: Caoxinhua <[e-mail]>

(gdb) bt
#0 0x00007f9a68b095d7 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
#1 0x00007f9a68b0acc8 in __GI_abort () at abort.c:90
#2 0x00007f9a69cda389 in PAT_abort () from /usr/lib64/libuvpuserhotfix.so
#3 0x00007f9a69cdda0d in patchIllInsHandler () from /usr/lib64/libuvpuserhotfix.so
#4 <signal handler called>
#5 pthread_setname_np (th=140298470549248, name=name@entry=0x8cc74a "io-task-worker") at ../nptl/sysdeps/unix/sysv/linux/pthread_setname.c:49
#6 0x00000000007f5f20 in qemu_thread_set_name (thread=thread@entry=0x7ffd2ac09680, name=name@entry=0x8cc74a "io-task-worker") at util/qemu_thread_posix.c:459
#7 0x00000000007f679e in qemu_thread_create (thread=thread@entry=0x7ffd2ac09680, name=name@entry=0x8cc74a "io-task-worker",start_routine=start_routine@entry=0x7c1300 <qio_task_thread_worker>, arg=arg@entry=0x7f99b8001720, mode=mode@entry=1) at util/qemu_thread_posix.c:498
#8 0x00000000007c15b6 in qio_task_run_in_thread (task=task@entry=0x7f99b80033d0, worker=worker@entry=0x7bd920 <qio_channel_socket_connect_worker>, opaque=0x7f99b8003370, destroy=0x7c6220 <qapi_free_SocketAddress>) at io/task.c:133
#9 0x00000000007bda04 in qio_channel_socket_connect_async (ioc=0x7f99b80014c0, addr=0x37235d0, callback=callback@entry=0x54ad00 <qemu_chr_socket_connected>, opaque=opaque@entry=0x38118b0, destroy=destroy@entry=0x0) at io/channel_socket.c:191
#10 0x00000000005487f6 in socket_reconnect_timeout (opaque=0x38118b0) at qemu_char.c:4402
#11 0x00007f9a6a1533b3 in g_timeout_dispatch () from /usr/lib64/libglib-2.0.so.0
#12 0x00007f9a6a15299a in g_main_context_dispatch () from /usr/lib64/libglib-2.0.so.0
#13 0x0000000000747386 in glib_pollfds_poll () at main_loop.c:227
#14 0x0000000000747424 in os_host_main_loop_wait (timeout=404000000) at main_loop.c:272
#15 0x0000000000747575 in main_loop_wait (nonblocking=nonblocking@entry=0) at main_loop.c:520
#16 0x0000000000557d31 in main_loop () at vl.c:2170
#17 0x000000000041c8b7 in main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at vl.c:5083

That's because the corresponding child thread has been exited before the main thread calling qemu_thread_set_name().
Let's detach the thread after calling qemu_thread_set_name().

Signed-off-by: Caoxinhua <[e-mail]>
---
 util/qemu-thread-posix.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

Comments

Stefan Hajnoczi Jan. 3, 2017, 4:06 p.m. UTC | #1

Please follow the conventions for commit messages.  QEMU commit messages
start with a prefix that identifies the affected component.

(Use git-log(1) to check what prefix other people have used for the
file(s) you touched.)

The commit message should be brief and doesn't need to be a full
sentence.

For example:

  qemu-thread: fix qemu_thread_set_name() race in qemu_thread_create()

Thanks,
Stefan

Zhanghailiang Jan. 4, 2017, 1:12 a.m. UTC | #2

Oops, I deleted the original  title carelessly, will send V2. Thanks.

On 2017/1/4 0:06, Stefan Hajnoczi wrote:
> Please follow the conventions for commit messages.  QEMU commit messages
> start with a prefix that identifies the affected component.
>
> (Use git-log(1) to check what prefix other people have used for the
> file(s) you touched.)
>
> The commit message should be brief and doesn't need to be a full
> sentence.
>
> For example:
>
>    qemu-thread: fix qemu_thread_set_name() race in qemu_thread_create()
>
> Thanks,
> Stefan

Patch

diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
index d20cdde..d31793d 100644
--- a/util/qemu-thread-posix.c
+++ b/util/qemu-thread-posix.c
@@ -481,12 +481,6 @@  void qemu_thread_create(QemuThread *thread, const char *name,
     if (err) {
         error_exit(err, __func__);
     }
-    if (mode == QEMU_THREAD_DETACHED) {
-        err = pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
-        if (err) {
-            error_exit(err, __func__);
-        }
-    }
 
     /* Leave signal handling to the iothread.  */
     sigfillset(&set);
@@ -499,6 +493,12 @@  void qemu_thread_create(QemuThread *thread, const char *name,
         qemu_thread_set_name(thread, name);
     }
 
+    if (mode == QEMU_THREAD_DETACHED) {
+        err = pthread_detach(thread->thread);
+        if (err) {
+            error_exit(err, __func__);
+        }
+    }
     pthread_sigmask(SIG_SETMASK, &oldset, NULL);
 
     pthread_attr_destroy(&attr);