From: Corinna Vinschen <corinna-cygwin@cygwin.com>
To: Takashi Yano <takashi.yano@nifty.ne.jp>
Cc: cygwin@cygwin.com
Subject: Re: Memory Barriers at pthread using CYGWIN
Date: Thu, 22 Jun 2023 13:48:53 +0200 [thread overview]
Message-ID: <ZJQ1JYyz9Wu+x5XA@calimero.vinschen.de> (raw)
In-Reply-To: <20230622191959.a8ff48a0e1f1221c6de52a87@nifty.ne.jp>
On Jun 22 19:19, Takashi Yano via Cygwin wrote:
> Any suggestions?
>
> On Tue, 20 Jun 2023 21:53:00 +0900
> Takashi Yano wrote:
> > I looked into this problem, and I think this is a problem regarding
> > _my_tls initialization order, so far. This seems to happen in LDAP
> > environment.
> >
> > My assumption is:
> >
> > If the program is the first program which load cygwin1.dll, ldap
> > connection seems to be made before pthread::init_mainthread().
> > In cyg_ldap.cc, cyg_ldap::connect(), cyg_ldap::search() or
> > cyg_ldap::next_page() calls cygwait() in which pthread::self()
> > is called.
> >
> > Then, _my_tls.tid is initialized with null_pthread, therefore,
> > _my_tls.tid is not set in pthread::init_mainthread().
> >
> > This causes pthread_join() failure at:
> > winsup/cygwin/thread.cc: line 2196
> > if (!is_good_object (&joiner))
> > return EINVAL;
> >
> >
> > The first idea to fix this issue is remove set_tls_self_pointer()
> > call from pthread::self().
> >
> > diff --git a/winsup/cygwin/thread.cc b/winsup/cygwin/thread.cc
> > index 5c1284a93..a0f2d5546 100644
> > --- a/winsup/cygwin/thread.cc
> > +++ b/winsup/cygwin/thread.cc
> > @@ -392,10 +392,7 @@ pthread::self ()
> > {
> > pthread *thread = _my_tls.tid;
> > if (!thread)
> > - {
> > - thread = pthread_null::get_null_pthread ();
> > - thread->set_tls_self_pointer ();
> > - }
> > + thread = pthread_null::get_null_pthread ();
> > return thread;
> > }
> >
> >
> > The secnd approach is to re-initialize _my_tls.tid in
> > pthread::init_mainthread() if _my_tls.tid is null_pthread.
> >
> > diff --git a/winsup/cygwin/thread.cc b/winsup/cygwin/thread.cc
> > index 5c1284a93..f614e01c4 100644
> > --- a/winsup/cygwin/thread.cc
> > +++ b/winsup/cygwin/thread.cc
> > @@ -364,7 +364,7 @@ void
> > pthread::init_mainthread ()
> > {
> > pthread *thread = _my_tls.tid;
> > - if (!thread)
> > + if (!thread || thread == pthread_null::get_null_pthread ())
> > {
> > thread = new pthread ();
> > if (!thread)
> >
> >
> > Which is the better approach, do you think?
> > Or any other idea?
The second approach looks good to me. There was a reason to call
set_tls_self_pointer from pthread::self, I guess. Resetting in
init_mainthread should have the least potential for side-effects.
Thanks,
Corinna
next prev parent reply other threads:[~2023-06-22 11:48 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAPxKPA6bRfF19pXrYT04TqbxettyYf=ypgfdySysqAJyB9BfxA@mail.gmail.com>
[not found] ` <CAPxKPA48sKPqwGc-jU7UQvQhsbT0N6A9LJXCAZeaa1rjeRtuNg@mail.gmail.com>
[not found] ` <96718c68-af84-45a5-9332-337ec4b2f04a@email.android.com>
2023-06-09 12:25 ` Takashi Yano
[not found] ` <64831a27.170a0220.1f805.81bfSMTPIN_ADDED_BROKEN@mx.google.com>
2023-06-10 4:08 ` Takashi Yano
2023-06-20 12:53 ` Takashi Yano
2023-06-22 10:19 ` Takashi Yano
2023-06-22 11:48 ` Corinna Vinschen [this message]
2023-06-22 23:49 ` Takashi Yano
2023-06-08 14:29 Mümin A.
2023-06-08 14:37 ` [EXTERNAL] " Lavrentiev, Anton (NIH/NLM/NCBI) [C]
2023-06-08 22:58 ` Mümin A.
2023-06-09 0:22 ` Takashi Yano
2023-06-09 1:44 ` Duncan Roe
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