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Message-ID: <29495f1d0511071144t1c917ae1v93cf72da11ad45c7@mail.gmail.com>
Date: Mon, 7 Nov 2005 11:44:17 -0800
From: Nish Aravamudan <nish.aravamudan@gmail.com>
To: Ram Gupta <ram.gupta5@gmail.com>
Subject: Re: negative timeout can be set up by setsockopt system call
Cc: linux-kernel@vger.kernel.org
In-Reply-To: <436FAB32.20807@gmail.com>
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On 11/7/05, Ram Gupta <ram.gupta5@gmail.com> wrote:
>
> On 11/7/05, Ram Gupta <ram.gupta5@gmail.com> wrote:
>  > On 11/4/05, Nish Aravamudan <nish.aravamudan@gmail.com>
>  >  >
>  >  > In Ram's specific case, I think, the call path is sys_setsockopt() ->
>  >  > sock_setsockopt() -> sock_set_timeout, which has a definition of:
>  >  >
>  >  > static int sock_set_timeout(long *timeo_p, char __user *optval, int
>  > optlen)
>  >
>  >  >> Exactly right.
>
> Ok.
>
>  >  > Ram, what is the expected behavior of negative values in the timeval?
>  >  > And what are you seeing happen right now?
>  >  >
>  >  > As of 2.6.14, looks like we convert any non-zero values into jiffies
>  >  > and store them in sk->sk_{rcv,snd}timeo...
>  >  >
>  >  I don't see any problem from the kernel side but the application
>  > times out immediately causing certain failures as the schedule_timeout
>  > returns immediately in case of negative values. Shouldn't there be a
>  > check for negative values and return error to the application so that
>  > it can handle it.
>
> I mean more along the lines of what does a man-page say the kernel
> should be doing if you request a negative timeout? More explicitly,
> what made you think negative timeouts should have a specific effect?
>
>  > The man page is silent about the timeout behaviour in case of its
> > being negative.  I believe that negative timeout is a mistake on behalf
> > of an application and hence should be treated as such (i.e should be
> > notified accordingly)

Well, the problem is that there is no defined behavior for specifying
a negative timeout (unlike poll(), for instance). So I'm not sure what
the best approach is (beyond complaining to the application developers
that their app is busted).

> When you say schedule_timeout() returns immediately, I assume your
> logs are filling up with "schedule_timeout: wrong timeout ..." ? (You
> may need to bump your loglevel). If not, then schedule_timeout() isn't
> getting a negative value.
>
>  >> Yes  I am getting the "schedule_timeout: wrong timeout ..."
> messages so I am sure the timeout has negative value.

Ok, maybe bring this up with the networking folks, as they may have a
better idea of what to do.

Thanks,
Nish
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