pthread_kill: signals remain pending after target thread exits
Fri Oct 23 14:30:00 GMT 2015
On Oct 22 02:08, John Carey wrote:
> > From: Corinna Vinschen [firstname.lastname@example.org]
> > Sent: Wednesday, October 21, 2015 4:48 AM
> > Subject: Re: pthread_kill: signals remain pending after target thread exits
> > > On Sep 11 18:11, John Carey wrote:
> > > There seems to be a problem with pthread_kill: a pending signal
> > > targeting a particular thread prevents other threads from receiving
> > > signals sharing the same signal number--even after the original target
> > > thread exits and is joined.
> > The important thing here is to get rid of the pending signal.
> Yes, I agree that is the most important thing.
> > > In my view it would be desirable if:
> > >
> > > - Pending signals targeting a particular thread would not outlast
> > > that thread.
> > Since you looked into the code anyway, do you have an idea how to
> > implement that? For a start, do you have a simple testcase, only
> > the bare code needed to reproduce the issue?
> I've attached a test case that I *think* gets into the right spot, at
> least for 64-bit Cygwin 2.0.4. That is, it hangs trying to receive
> the signal, instead of terminating. (This test passes (terminates) in
> 32-bit Cygwin 1.7.9 and 64-bit Ubuntu 14.04.3 LTS.)
Thanks for the testcase. I applied a patch which hopefully works as
desired, at least to fix the immediate problem of the remaining pending
signal when a thread exits. I uploaded a new developer snapshot to
https://cygwin.com/snapshots. Please give it a try.
Note that the today's snapshot does *NOT* contain the changes concerning
the new ACL handling, so people testing that stuff should skip this
> > > - Multiple pending signals targeting different threads could
> > > coexist, even if they shared the same signal number. This happens
> > > on Linux (Ubuntu 14.04.3), where I can generate two signals for two
> > > different threads, then sleep for a bit in each target thread, and
> > > finally have each thread receive its signal with sigwait()--neither
> > > signal is lost during the sleeping period.
> > That requires to extend the handling for pending signals. That's
> > a rather bigger task...
> Yeah. It's nice if threads don't interfere with each other, but this
> part would indeed be harder to change.
I added that to my neverending TODO list. Maybe I get around to it at
Corinna Vinschen Please, send mails regarding Cygwin to
Cygwin Maintainer cygwin AT cygwin DOT com
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