From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49828) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cP3SF-0001m7-9N for qemu-devel@nongnu.org; Thu, 05 Jan 2017 03:31:24 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cP3SE-0005LL-AV for qemu-devel@nongnu.org; Thu, 05 Jan 2017 03:31:23 -0500 References: <1483493521-9604-1-git-send-email-zhang.zhanghailiang@huawei.com> <20170104103227.GD10541@redhat.com> From: Hailiang Zhang Message-ID: <586E0426.6040701@huawei.com> Date: Thu, 5 Jan 2017 16:30:30 +0800 MIME-Version: 1.0 In-Reply-To: <20170104103227.GD10541@redhat.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2] qemu-thread: fix qemu_thread_set_name() race in qemu_thread_create() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Daniel P. Berrange" Cc: xuquan8@huawei.com, qemu-devel@nongnu.org, stefanha@gmail.com, qemu-stable@nongnu.org, Caoxinhua , arei.gonglei@huawei.com, pbonzini@redhat.com On 2017/1/4 18:32, Daniel P. Berrange wrote: > On Wed, Jan 04, 2017 at 09:32:01AM +0800, zhanghailiang wrote: >> From: Caoxinhua >> >> 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 (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 >> #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 , 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 , opaque=0x7f99b8003370, destroy=0x7c6220 ) at io/task.c:133 >> #9 0x00000000007bda04 in qio_channel_socket_connect_async (ioc=0x7f99b80014c0, addr=0x37235d0, callback=callback@entry=0x54ad00 , 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=, argv=, envp=) at vl.c:5083 >> >> Let's detach the new thread after calling qemu_thread_set_name(). >> >> Signed-off-by: Caoxinhua >> --- >> v2: >> Fix missing title >> --- >> 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__); >> + } >> + } > Is it permitted to be calling pthread_detach(), if there is a chance that > the thread has already exited ? It seems reasonable, since a non-detached Yes, there is no problem if we call pthread_detach() after the related thread has exited, we have tested it. Thanks, Hailiang > thread shouldl remain in a zombie state waiting to be join'd, but the man > page is unclear on behaviour. > > Regards, > Daniel