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cpus: use broadcast on qemu_pause_cond

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Jiri saw a hang on pause_all_vcpus called from postcopy_start,
where the cpus are all apparently stopped ('stopped' flag set)
but pause_all_vcpus is still stuck on a cond_wait on qemu_paused_cond.
We suspect this is happening if a qmp_stop is called at about the
same time as the postcopy code calls that pause_all_vcpus;
although they both should have the main lock held, Paolo spotted
the cond_wait unlocks the global lock so perhaps they both
could end up waiting at the same time?

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reported-by: Jiri Denemark <jdenemar@redhat.com>
Message-Id: <1453716498-27238-1-git-send-email-dgilbert@redhat.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Dr. David Alan Gilbert 2016-01-25 10:08:18 +00:00 committed by Paolo Bonzini
parent a013bd2f7b
commit 96bce6831b
1 changed files with 2 additions and 2 deletions
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4
cpus.c
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@ -986,7 +986,7 @@ static void qemu_wait_io_event_common(CPUState *cpu)
if (cpu->stop) {
cpu->stop = false;
cpu->stopped = true;
qemu_cond_signal(&qemu_pause_cond);
qemu_cond_broadcast(&qemu_pause_cond);
}
flush_queued_work(cpu);
cpu->thread_kicked = false;
@ -1387,7 +1387,7 @@ void cpu_stop_current(void)
current_cpu->stop = false;
current_cpu->stopped = true;
cpu_exit(current_cpu);
qemu_cond_signal(&qemu_pause_cond);
qemu_cond_broadcast(&qemu_pause_cond);
}
}