On Wed, Oct 10, 2018 at 10:40:12PM -0700, Nicholas A. Bellinger wrote: > Hey Peter & Co, > > On Wed, 2018-10-10 at 10:43 +0200, Peter Zijlstra wrote: > > On Wed, Oct 10, 2018 at 03:23:10AM +0000, Nicholas A. Bellinger wrote: > > > From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx> > > > > > > With the addition of commit 00d909a107 in v4.19-rc, it incorrectly assumes no > > > signals will be pending for task_struct executing the normal session shutdown > > > and I/O quiesce code-path. > > > > > > For example, iscsi-target and iser-target issue SIGINT to all kthreads as > > > part of session shutdown. This has been the behaviour since day one. > > > > Not knowing much context here; but does it make sense for those > > kthreads to handle signals, ever? Most kthreads should be fine with > > ignore_signals(). > > > > iscsi-target + ib-isert uses SIGINT amongst dedicated rx/tx connection > kthreads to signal connection shutdown, requiring in-flight se_cmd I/O > descriptors to be quiesced before making forward progress to release > se_session. > > By the point wait_event_lock_irq_timeout() is called in the example > here, one of the two rx/tx connection kthreads has been stopped, and the > other kthread is still processing shutdown. So while historically the > pending SIGINTs where not cleared (or ignored) during shutdown at this > point, there is no reason why they could not be ignored for iscsi-target > + ib-isert. > > That said, pre commit 00d909a107 code always used wait_for_completion() > and ignored pending signals. As-is target_wait_for_sess_cmds() is > called directly from fabric driver code and in one case also from > user-space via configfs_write_file(), so AFAICT it does need > TASK_UNINTERRUPTIBLE. > Fair enough, thanks for the background. I'm always a bit wary when kthreads need to deal with signals, but this seems OK.
