Author: cem
Date: Fri Nov 11 20:09:54 2016
New Revision: 308553
URL: https://svnweb.freebsd.org/changeset/base/308553
Log:
ioat(4): Fix race between process_events and reset_hw
In the case where a hardware error is detected during
ioat_process_events, hardware may advance (by one descriptor, probably)
and a subsequent ioat_process_events may race the intended ioat_reset_hw
followup. In that case, the second process_events would observe a
completion update that does not match the software "last_seen" status,
and attempt to successfully complete already-failed descriptors.
Guard against this race with the resetting_cleanup flag.
Reviewed by: bdrewery, markj
Sponsored by: Dell EMC Isilon
Modified:
head/sys/dev/ioat/ioat.c
Modified: head/sys/dev/ioat/ioat.c
==============================================================================
--- head/sys/dev/ioat/ioat.c Fri Nov 11 20:08:45 2016 (r308552)
+++ head/sys/dev/ioat/ioat.c Fri Nov 11 20:09:54 2016 (r308553)
@@ -765,6 +765,15 @@ out:
mtx_lock(&ioat->submit_lock);
mtx_lock(&ioat->cleanup_lock);
ioat->quiescing = TRUE;
+ /*
+ * This is safe to do here because we have both locks and the submit
+ * queue is quiesced. We know that we will drain all outstanding
+ * events, so ioat_reset_hw can't deadlock. It is necessary to
+ * protect other ioat_process_event threads from racing ioat_reset_hw,
+ * reading an indeterminate hw state, and attempting to continue
+ * issuing completions.
+ */
+ ioat->resetting_cleanup = TRUE;
chanerr = ioat_read_4(ioat, IOAT_CHANERR_OFFSET);
if (1 <= g_ioat_debug_level)
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