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[Qemu-devel] [PULL 20/35] qemu-thread: fix qemu_thread_set_name() race i


From: Paolo Bonzini
Subject: [Qemu-devel] [PULL 20/35] qemu-thread: fix qemu_thread_set_name() race in qemu_thread_create()
Date: Fri, 20 Jan 2017 14:31:24 +0100

From: Caoxinhua <address@hidden>

QEMU will crash with the follow backtrace if the new created thread exited 
before
we call qemu_thread_set_name() for it.

  (gdb) bt
  #0 0x00007f9a68b095d7 in __GI_raise (address@hidden) 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, address@hidden "io-task-worker") 
at ../nptl/sysdeps/unix/sysv/linux/pthread_setname.c:49
  #6 0x00000000007f5f20 in qemu_thread_set_name (address@hidden, address@hidden 
"io-task-worker") at util/qemu_thread_posix.c:459
  #7 0x00000000007f679e 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:498
  #8 0x00000000007c15b6 in qio_task_run_in_thread (address@hidden, 
address@hidden <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, address@hidden 
<qemu_chr_socket_connected>, address@hidden, address@hidden) 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 (address@hidden) 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

Let's detach the new thread after calling qemu_thread_set_name().

Signed-off-by: Caoxinhua <address@hidden>
Signed-off-by: zhanghailiang <address@hidden>
Message-Id: <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
 util/qemu-thread-posix.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

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);
-- 
2.9.3





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