sigwait return 4
slw at zxy.spb.ru
Wed Aug 24 20:04:46 UTC 2011
On Wed, Aug 24, 2011 at 10:50:35PM +0300, Kostik Belousov wrote:
> On Wed, Aug 24, 2011 at 11:42:29PM +0400, Slawa Olhovchenkov wrote:
> > On Wed, Aug 24, 2011 at 10:32:02PM +0300, Kostik Belousov wrote:
> > > > > What should the system do for a delivered signal not present in the set ?
> > > > > I guess this is the case of your ktrace.
> > > > >
> > > > > Looking at the SUSv4, I see no mention of the situation, but in Oracle
> > > > > SunOS 5.10 man page for sigwait(2), it is said explicitely
> > > > > EINTR The wait was interrupted by an unblocked, caught signal.
> > > >
> > > > I don't think you right in this case.
> > > > This is kas-milter and in this thread (this is multi-thread
> > > > application) kas-milter wait for USR2 for reload config.
> > > >
> > > > System return from sigwait only on USR2, but not each return w/
> > > > non-zero return code.
> > > >
> > > > On freebsd7 this application don't complain about sigwait's return value.
> > >
> > > Could it be that some other thread has the signal unblocked ?
> > > (You can verify this with procstat -j).
> > >
> > > Can you write the self-contained test case that demonstrates the behaviour ?
> > This is closed-source software.
> How is this statement related to the creation of the standalone test case ?
I don't know what testing.
> > # procstat -j
> > PID TID COMM SIG FLAGS
> > 1395 100199 kas-milter USR2 --
> > 1395 100232 kas-milter USR2 --
> Both threads have the signal not blocked. This is not definitive,
> since signal must be blocked during the call to sigwait(2). Note that
> the SUSv4 says that "The signals defined by set shall have been
> blocked at the time of the call to sigwait(); otherwise, the behavior is
This is not suitable to return '4'.
And where root of this '4'?
In /sys/kern/kern_sig.c:sigwait we call
error = kern_sigtimedwait(td, set, &ksi, NULL); --- no timeout.
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