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Postings from April 2010
Attached is a self-contained script that reproduces the problem.
Mostly it hangs
at line 47 (before the 'Debug: not hung' message). However, it
occasionally hangs
at other places (e.g., trying to lock %SUSPEND). Frequently, the script runs to
completion, but it does hang after a few runs.
I think there is some nasty interplay between threads::shared locks and the
PERL_ASYNC_CHECK() calls. If I change the thread subroutine to change the
delete() to something else, I don't get the hangs.
On Tue, Apr 20, 2010 at 14:55, Jerry D. Hedden <jdhedden@cpan.org> wrote:
>> +Signal dispatch has been moved from the runloop into control ops. This should
>> +give a few percent speed increase, and eliminates almost all of the speed
>> +penalty caused by the introduction of "safe signals" in 5.8.0. Signals should
>> +still be dispatched within the same statement as they were previously - if
>> +this is not the case, or it is possible to create uninterruptable loops, this
>> +is a bug, and reports are encouraged of how to recreate such issues.
>
> Since the PERL_ASYNC_CHECK() changes were made to blead, my module
> Thread::Suspend has been hanging during 'make test'. I found that it
> hangs in a most peculiar spot: Right after an 'if' statement inside a
> a 'for loop'. When I put debug statements in, my code looks like this:
>
> sub threads::suspend
> {
> my ($thing, @threads) = @_;
>
> if ($thing eq 'threads') {
> if (@threads) {
> # Suspend specified list of threads
> @threads = grep { $_ }
> map { (ref($_) eq 'threads')
> ? $_
> : threads->object($_) }
> @threads;
> } else {
> # Suspend all non-detached threads
> push(@threads, threads->list(threads::running));
> }
> } else {
> # Suspend a single thread
> push(@threads, $thing);
> }
>
> # Suspend threads
> lock(%SUSPEND);
> foreach my $thr (@threads) {
> my $tid = $thr->tid();
> # Increment suspension count
> if (! $SUSPEND{$tid}++) {
> # Send suspend signal if not currently suspended
> $thr->kill($SIGNAL);
> if (! $thr->is_running()) {
> # Thread terminated before it could be suspended
> delete($SUSPEND{$tid});
> }
> print("Debug: sent signal\n");
> }
> print("Debug: not hung\n");
> }
>
> # Return list of affected threads
> return ($thing eq 'threads')
> ? grep { $_->is_running() } @threads
> : $thing;
> }
>
>
> When I run the test, I get:
>
>> perl -Ilib t/00_basic.t
> 1..57
> ok 1 - use Thread::Suspend;
> # Testing Thread::Suspend 1.19
> ok 2 - threads->can(...)
> ok 3 - Threads created
> ok 4 - No threads suspended
> ok 5 - Thread 1 not suspended
> ok 6 - Thread 1 running (line 48)
> Debug: sent signal
> Debug: not hung
> ok 7 - One thread suspended
> ok 8 - Thread 1 suspended
> ok 9 - Thread 1 suspended
> ok 10 - Thread 1 stopped (line 54)
> Debug: not hung
> ok 11 - One thread suspended
> ok 12 - Thread 1 suspended
> ok 13 - Thread 1 suspended twice
> ok 14 - Thread 1 stopped (line 60)
> ok 15 - One thread suspended
> ok 16 - Thread 1 suspended
> ok 17 - Thread 1 still suspended
> ok 18 - Thread 1 stopped (line 66)
> ok 19 - No threads suspended
> ok 20 - Thread 1 not suspended
> ok 21 - Thread 1 running (line 71)
> ok 22 - No threads suspended
> ok 23 - Thread 2 not suspended
> ok 24 - Thread 2 running (line 48)
> Debug: sent signal
>
>
> The test is now hung and I have to hit ^C. This is
> very repeatable for me.
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