Another pipe-related problem?
Takashi Yano
takashi.yano@nifty.ne.jp
Wed Nov 10 00:37:41 GMT 2021
On Wed, 10 Nov 2021 09:16:13 +0900
Takashi Yano wrote:
> On Wed, 10 Nov 2021 08:48:22 +0900
> Takashi Yano wrote:
> > On Wed, 10 Nov 2021 08:29:32 +0900
> > Takashi Yano wrote:
> > > On Wed, 10 Nov 2021 08:22:45 +0900
> > > Takashi Yano wrote:
> > > > On Tue, 9 Nov 2021 09:11:28 -0500
> > > > Ken Brown wrote:
> > > > > I'll have to reproduce the hang myself in order to test this (or maybe you could
> > > > > test it), but I now have a new guess: If the read call above keeps failing with
> > > > > EINTR, then we're in an infinite loop. This could happen because of the
> > > > > following code in fhandler_pipe::raw_read:
> > > > >
> > > > > DWORD waitret = cygwait (read_mtx, timeout);
> > > > > switch (waitret)
> > > > > {
> > > > > case WAIT_OBJECT_0:
> > > > > break;
> > > > > case WAIT_TIMEOUT:
> > > > > set_errno (EAGAIN);
> > > > > len = (size_t) -1;
> > > > > return;
> > > > > default:
> > > > > set_errno (EINTR);
> > > > > len = (size_t) -1;
> > > > > return;
> > > > > }
> > > > >
> > > > > Takashi, is EINTR really the appropriate errno in the default case? Isn't
> > > > > cygwait supposed to handle signals?
> > > >
> > > > I assume cygwait() returns WAIT_SIGNALED when signalled
> > > > by SIGINT, SIGTERM, SIGTSTP, etc... In this case, EINTR
> > > > should return I think.
> > > >
> > > > Is it wrong?
> > >
> > > Ah, if SA_RESTART is set, we should continue to read even
> > > if signalled...
[...]
> No, we don't have to do that because cygwait() do the same
> internally. cygwain() returns WAIT_SIGNALED when signalled
> only if SA_RESTART is not set. So, the current code LGTM.
Ah, however, should we handle WAIT_CANCELED here and call
pthread::static_cancel_self() as following?
DWORD waitret = cygwait (read_mtx, timeout);
switch (waitret)
{
case WAIT_OBJECT_0:
break;
case WAIT_TIMEOUT:
set_errno (EAGAIN);
len = (size_t) -1;
return;
WAIT_SIGNALED:
set_errno (EINTR);
len = (size_t) -1;
return;
WAIT_CANCELED:
pthread::static_cancel_self ();
/* NOTREACHED */
default:
/* Should not reach here. */
__seterrno ();
len = (slze_t) -1;
return;
}
--
Takashi Yano <takashi.yano@nifty.ne.jp>
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