>Hi Wang Yong,>>To make the discussion easier, please try to fix your email >client to:>>1) set In-Reply-To: header when replying>2) use plain text instead >of html>3) use monospace fonts to view and compose a reply>4) avoid attaching >the original email in the end, just reply inline>5) maybe, use "Re:" in the >subject for reply, avoid "答复:">6) include not only email addresses in >From:To:/Cc: headers, but also> the names of recipients, in the form of>> > Some Body <some.b...@example.com>, Another One <another....@example.com>,> > ...>Or maybe just switch to a functional email client.
Hi Fam,I am very sorry that our company's mail client does not support the part. >> I think it's ok, I don't know whether I understand it correctly or >> not?>>Your sequence is ok. But remember this is multi-threaded and the >> execution order>between two threads are non-deterministic. The sequence I >> pointed out is also>"possible" and will cause use-after-free due to TOCTOU >> race condition [1].>>[1]: >> https://en.wikipedia.org/wiki/Time_of_check_to_time_of_use Thanks,When iothread_stop is called two times concurrently,this BUG may be triggered. I will submit the patch v5. WangYong 原始邮件 发件人： <f...@redhat.com> 收件人：王勇10170530 抄送人： <pbonz...@redhat.com> <stefa...@redhat.com> <jasow...@redhat.com> <zhangchen.f...@cn.fujitsu.com> <zhang.zhanghaili...@huawei.com>王广10165992 <lizhij...@cn.fujitsu.com> <qemu-devel@nongnu.org> 日 期 ：2017年08月23日 16:43 主 题 ：Re: 答复: Re: [PATCHv4 01/03] qemu-iothread: IOThread supports theGMainContext event loop Hi Wang Yong, To make the discussion easier, please try to fix your email client to: 1) set In-Reply-To: header when replying 2) use plain text instead of html 3) use monospace fonts to view and compose a reply 4) avoid attaching the original email in the end, just reply inline 5) maybe, use "Re:" in the subject for reply, avoid "答复:" 6) include not only email addresses in From:To:/Cc: headers, but also the names of recipients, in the form of Some Body <some.b...@example.com>, Another One <another....@example.com>, ... Or maybe just switch to a functional email client. On Wed, 08/23 15:58, wang.yong...@zte.com.cn wrote: > >> diff --git a/iothread.c b/iothread.c>> index beeb870..fb1c55b 100644>> --- > >> a/iothread.c>> +++ b/iothread.c>> @@ -57,6 +57,20 @@ static void > >> *iothread_run(void *opaque)>> >> while > >> (!atomic_read(&iothread->stopping)) {>> aio_poll(iothread->ctx, > >> true)>> +>> + if (atomic_read(&iothread->worker_context)) {>> + > >> g_main_context_push_thread_default(iothread->worker_context)>> + > >> iothread->main_loop =>> + > >> g_main_loop_new(iothread->worker_context, TRUE)>> + > >> g_main_loop_run(iothread->main_loop)>> +>> + > >> g_main_loop_unref(iothread->main_loop)>> + iothread->main_loop > >> = NULL> > > >You should clear iothread->main_loop first before calling > >g_main_loop_unref(),>to avoid TOCTOU race with iothread_stop():> > > > iothread_run (in IOThread) iothread_stop (in main thread)> > > ========================================================================> > > if (atomic_read(&iothread->main_loop)) {> > > /* frees iothread->main_loop */> g_main_loop_unref(...)> > > /* Accesses freed memory */> > > g_main_loop_quit(iothread->main_loop)> > > }> iothread->main_loop = NULL > > When the g_main_loop_quit function is called, the g_main_loop_run function > can exit? > > > > > iothread_run (in IOThread) > iothread_stop (in main thread) > > ======================================================================== > > > /*step1: set loop->is_running = FALSE*/ > > > g_main_loop_quit(iothread->main_loop) > > /*step2: main loop exit */ > > > > g_main_loop_run() > > /*step3:frees iothread->main_loop memory*/ > > g_main_loop_unref(...) > > iothread->main_loop = NULL > > > > > I think it's ok, I don't know whether I understand it correctly or not? Your sequence is ok. But remember this is multi-threaded and the execution order between two threads are non-deterministic. The sequence I pointed out is also "possible" and will cause use-after-free due to TOCTOU race condition [1]. [1]: https://en.wikipedia.org/wiki/Time_of_check_to_time_of_use Fam
