Hi Mikulas, On Mon, 2014-06-23 at 13:42 -0400, Mikulas Patocka wrote: > target: fix deadlock on unload > > On uniprocessor preemptible kernel, target core deadlocks on unload. The > following events happen: > * iscsit_del_np is called > * it calls send_sig(SIGINT, np->np_thread, 1); > * the scheduler switches to the np_thread > * the np_thread is woken up, it sees that kthread_should_stop() returns > false, so it doesn't terminate > * the np_thread clears signals with flush_signals(current); and goes back > to sleep in iscsit_accept_np > * the scheduler switches back to iscsit_del_np > * iscsit_del_np calls kthread_stop(np->np_thread); > * the np_thread is waiting in iscsit_accept_np and it doesn't respond to > kthread_stop > > The deadlock could be resolved if the administrator sends SIGINT signal to > the np_thread with killall -INT iscsi_np > > The reproducible deadlock was introduced in commit > db6077fd0b7dd41dc6ff18329cec979379071f87, but the thread-stopping code was > racy even before. > > This patch fixes the problem. Using kthread_should_stop to stop the > np_thread is unreliable, so we test np_thread_state instead. If > np_thread_state equals ISCSI_NP_THREAD_SHUTDOWN, the thread exits. > > Signed-off-by: Mikulas Patocka <mpato...@redhat.com> > Cc: sta...@vger.kernel.org >
Apologies for the delayed response.. Applied to target-pending/master and including in the next -rc3 PULL request. Also FYI, I've added '3.12+' to the stable tag to match how far back commit db6077fd0 has been included in stable. Thanks, --nab -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
