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From: Michael Kerrisk <mtk-manpages@gmx•net>
To: Andi Kleen <andi@firstfloor•org>
Cc: Shay Goikhman <GOIKHMAN@il•ibm.com>,
	netdev@vger•kernel.org, davem@davemloft•net
Subject: Re: Problem with semantics?
Date: Mon, 27 Aug 2007 17:46:09 +0200	[thread overview]
Message-ID: <46D2F1C1.2050606@gmx.net> (raw)
In-Reply-To: <p737inzne6i.fsf@bingen.suse.de>

Hi Andi,

Andi Kleen wrote:
> Shay Goikhman <GOIKHMAN@il•ibm.com> writes:
> 
>> Dear Linux maintainers,
>>
>>  I'm doing :
>>
>>       setsockopt(s,  SO_RCVTIMEO, t1 );                  // set time-out
>> t1 on socket while block receiving on it
>>       select(,,, &fd_set_including(s), .., &errs, t2);      // block till
>> receive or time-out  t 2 jointly on a set of sockets
>>
>> Apparently, I could no find reference on the coupled behavior of the two
>> above statements in Linux documentation.
>> As I understand the blocking semantics, I would expect  that  if t1<t2 ,
>> select should return after t1 with the descriptor 's' in 'errs' if 's' does
>> not become readable in the t1 interval.
>>
>> It is not so in life -- select ignores t1 altogether.
>>
>> Do you have some enlightening knowledge on the matter?
> 
> RCVTIMEO only applies to recvmsg et.al., similar to SNDTIMEO only
> apply to sendmsg etc. But select/poll only report events, they
> do not actually send or receive by themselves.
> 
> Michael, perhaps you can clarify that in the manpages

I added the following to sockets.7:

              Timeouts have
              effect   for  socket  I/O  calls  (read(2),  recv(2),
              recvfrom(2),    recvmsg(2),    write(2),     send(2),
              sendto(2),  sendmsg(2));  timeouts have no effect for
              select(2), poll(2), epoll_wait(2), etc.

The change will be in man-pages-2.65.

Thanks for your note.

Cheers,

Michael

-- 
Michael Kerrisk
maintainer of Linux man pages Sections 2, 3, 4, 5, and 7

Want to help with man page maintenance?  Grab the latest tarball at
http://www.kernel.org/pub/linux/docs/manpages/
read the HOWTOHELP file and grep the source files for 'FIXME'.

     prev parent reply	other threads:[~2007-08-27 15:48 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-08-13 17:07 Problem with semantics? Shay Goikhman
2007-08-14  0:38 ` Andi Kleen
2007-08-27 15:46   ` Michael Kerrisk [this message]

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