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Date:      Wed, 30 Nov 2016 21:59:52 +0000 (UTC)
From:      "Conrad E. Meyer" <cem@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r309338 - head/sys/dev/ioat
Message-ID:  <201611302159.uAULxqBP057526@repo.freebsd.org>
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Author: cem
Date: Wed Nov 30 21:59:52 2016
New Revision: 309338
URL: https://svnweb.freebsd.org/changeset/base/309338

Log:
  ioat(4): Fix 'bogus completion_pending' KASSERT
  
  Fix ioat_release to only set is_completion_pending if DMAs were actually
  queued.  Otherwise, the spurious flag could trigger an assert in the
  reset path on INVARIANTS kernels.
  
  Reviewed by:	bdrewery, Suraj Raju @ Isilon
  Sponsored by:	Dell EMC Isilon

Modified:
  head/sys/dev/ioat/ioat.c
  head/sys/dev/ioat/ioat_internal.h

Modified: head/sys/dev/ioat/ioat.c
==============================================================================
--- head/sys/dev/ioat/ioat.c	Wed Nov 30 21:53:06 2016	(r309337)
+++ head/sys/dev/ioat/ioat.c	Wed Nov 30 21:59:52 2016	(r309338)
@@ -947,6 +947,7 @@ ioat_acquire(bus_dmaengine_t dmaengine)
 	ioat = to_ioat_softc(dmaengine);
 	mtx_lock(&ioat->submit_lock);
 	CTR2(KTR_IOAT, "%s channel=%u", __func__, ioat->chan_idx);
+	ioat->acq_head = ioat->head;
 }
 
 int
@@ -976,12 +977,15 @@ ioat_release(bus_dmaengine_t dmaengine)
 	CTR4(KTR_IOAT, "%s channel=%u dispatch2 hw_head=%u head=%u", __func__,
 	    ioat->chan_idx, ioat->hw_head & UINT16_MAX, ioat->head);
 
-	ioat_write_2(ioat, IOAT_DMACOUNT_OFFSET, (uint16_t)ioat->hw_head);
-
-	if (!ioat->is_completion_pending) {
-		ioat->is_completion_pending = TRUE;
-		callout_reset(&ioat->poll_timer, 1, ioat_poll_timer_callback,
-		    ioat);
+	if (ioat->acq_head != ioat->head) {
+		ioat_write_2(ioat, IOAT_DMACOUNT_OFFSET,
+		    (uint16_t)ioat->hw_head);
+
+		if (!ioat->is_completion_pending) {
+			ioat->is_completion_pending = TRUE;
+			callout_reset(&ioat->poll_timer, 1,
+			    ioat_poll_timer_callback, ioat);
+		}
 	}
 	mtx_unlock(&ioat->submit_lock);
 }

Modified: head/sys/dev/ioat/ioat_internal.h
==============================================================================
--- head/sys/dev/ioat/ioat_internal.h	Wed Nov 30 21:53:06 2016	(r309337)
+++ head/sys/dev/ioat/ioat_internal.h	Wed Nov 30 21:59:52 2016	(r309338)
@@ -483,6 +483,7 @@ struct ioat_softc {
 	boolean_t		resetting_cleanup;	/* cleanup_lock */
 
 	uint32_t		head;
+	uint32_t		acq_head;
 	uint32_t		tail;
 	uint32_t		hw_head;
 	uint32_t		ring_size_order;

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