Re: [Qemu-devel] [Bug 955379] Re: cmake hangs with qemu-arm-static

[Peter Maydell]

On 4 December 2012 11:21, Janne Karhunen <address@hidden> wrote:
> And what would break if we make poll timeout instantly in case there are
> signals pending and restart the given syscall after handlers run?

If there are signals pending in the host kernel poll will *already*
return immediately. If there is a signal pending in the QEMU signal
queue (because the host kernel just delivered it to us) then there
will always be a window between the point where you say "ok, queue
is empty" and actually doing the host syscall, where a signal could
be delivered and put in the queue. You cannot fix this bug in the way
you are trying to: you must handle this case by longjumping out of
the signal handler. I've already sketched the correct design for
fixing this.

[to anybody in the peanut gallery who is thinking about pselect()
now: yes, you could perhaps hack something up with that, but it would
still be a big patch with a bunch of corner cases to review, and
it would only fix this bug for this particular syscall, not in
general.]

-- PMM