From: "Jan D." <jan.h.d@swipnet.se>
To: Eli Zaretskii <eliz@gnu.org>
Cc: Lars Magne Ingebrigtsen <larsi@gnus.org>, emacs-devel@gnu.org
Subject: Re: gnutls error handling
Date: Sun, 17 Oct 2010 18:21:14 +0200 [thread overview]
Message-ID: <4CBB227A.6010004@swipnet.se> (raw)
In-Reply-To: <E1P7V42-0003gq-2Q@fencepost.gnu.org>
Eli Zaretskii skrev 2010-10-17 17:22:
>> From: Lars Magne Ingebrigtsen<larsi@gnus.org>
>> Date: Sun, 17 Oct 2010 15:55:24 +0200
>> Mail-Copies-To: never
>>
>> poll([{fd=4, events=POLLIN}, {fd=3, events=POLLIN}], 2, 0) = 0 (Timeout)
>> select(15, [3 4 8 10 13], [], NULL, {0, 15591}) = 2 (in [8 10], left {0, 15589})
>> read(3, 0xec9b94, 4096) = -1 EAGAIN (Resource temporarily unavailable)
>> poll([{fd=4, events=POLLIN}, {fd=3, events=POLLIN}], 2, 0) = 0 (Timeout)
>> select(15, [3 4 8 10 13], [], NULL, {0, 15532}) = 2 (in [8 10], left {0, 15530})
>> read(3, 0xec9b94, 4096) = -1 EAGAIN (Resource temporarily unavailable)
>>
>> There's always a gnutls socket involved in the select call -- in this
>> instance it was fd 10. lsof showed the socket to be in the CLOSE_WAIT
>> state. So my suspicion is that the we're somehow now communicating back
>> to Emacs that a gnutls socket has closed.
> Not really a useful answer, but the `select' man page has this piece
> of wisdom:
>
> Under Linux, select() may report a socket file descriptor as
> "ready for reading", while nevertheless a subsequent read
> blocks. This could for example happen when data has arrived
> but upon examination has wrong checksum and is discarded.
> There may be other circumstances in which a file descriptor is
> spuriously reported as ready. Thus it may be safer to use
> O_NONBLOCK on sockets that should not block.
>
> Of course, we already use O_NONBLOCK (AFAIK).
The question is why is Emacs reading fd 3? It is not reported as ready
by select, fd 8 and 10 are ready, but those aren't read.
Jan D.
next prev parent reply other threads:[~2010-10-17 16:21 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-17 13:55 gnutls error handling Lars Magne Ingebrigtsen
2010-10-17 15:22 ` Eli Zaretskii
2010-10-17 16:21 ` Jan D. [this message]
2010-10-17 17:05 ` Lars Magne Ingebrigtsen
2010-10-17 17:18 ` Lars Magne Ingebrigtsen
2010-10-17 18:43 ` Eli Zaretskii
2010-10-17 18:50 ` Lars Magne Ingebrigtsen
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