Re: sigtimedwait with a zero timeout

From: Henrik Nordstrom (hno@hem.passagen.se)
Date: Mon Oct 02 2000 - 01:31:49 EST

You are not late. In fact you are the first who have responded to my
linux-kernel messages at all.

Yes, I am well aware of sigwaitinfo.

sigwaitinfo blocks infinitely if there is no queued signals and is the
opposite of sigtimedwait with a zero timeout.

sigwaitinfo is implemented as sigtimedwait with a NULL timeout which is
read as a timeout of MAX_SCHEDULE_TIMEOUT.

sigtimedwait with a zero timeout are meant to be used by applications
needing to poll signal queues while doing other processing. Having
sigtimedwait always block for at least 10 ms can have a quite negative
impact on such applications.

Pleae note that the first version of my patch was quite broken. A
corrected version was posted a few days later.

Thanks for your interest. 

--
Henrik Nordstrom

James Antill wrote:
> 
> Henrik Nordstrom <hno@hem.passagen.se> writes:
> 
> > Hi.
> >
> > While playing with signal queues it was discovered that sigtimedwait
> > with a zero timeout apparently does block somewhat even if it should
> > not.
> >
> > Why:
> >
> > It forces a schedule()
> 
>  This is a bit late (catching up with mail). But you know about
> sigwaitinfo() yeh ?
> 
> --
> James Antill -- james@and.org
> "If we can't keep this sort of thing out of the kernel, we might as well
> pack it up and go run Solaris." -- Larry McVoy.

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