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SubjectRe: sigtimedwait with a zero timeout
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Henrik Nordstrom <hno@hem.passagen.se> writes:

> 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.

Yes, sorry that's what I thought you wanted to do (Ie. you new some
data was there and wanted to get it quickly).

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

Ahh I didn't know that.

> 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.

If you want to return imediatley (and there might not be data) the
answer given is usually...

sigqueue( ... );
sigwaitinfo( ... );

If the above will still schedule, then Linus might be more likely to
take a patch (I'd guess that he'd look at sigtimedwait() to be like
sleep() in most other cases though).

--
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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