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From: Sepherosa Ziehau <sephe@FreeBSD.org>
Date: Fri, 25 Nov 2016 06:12:18 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r309132 - head/sys/dev/hyperv/vmbus
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Author: sephe
Date: Fri Nov 25 06:12:18 2016
New Revision: 309132
URL: https://svnweb.freebsd.org/changeset/base/309132

Log:
  hyperv/vmbus: Don't close unopened channels.
  
  MFC after:	1 week
  Sponsored by:	Microsoft
  Differential Revision:	https://reviews.freebsd.org/D8566

Modified:
  head/sys/dev/hyperv/vmbus/vmbus_chan.c

Modified: head/sys/dev/hyperv/vmbus/vmbus_chan.c
==============================================================================
--- head/sys/dev/hyperv/vmbus/vmbus_chan.c	Fri Nov 25 06:01:45 2016	(r309131)
+++ head/sys/dev/hyperv/vmbus/vmbus_chan.c	Fri Nov 25 06:12:18 2016	(r309132)
@@ -688,10 +688,28 @@ vmbus_chan_close_internal(struct vmbus_c
 	struct vmbus_softc *sc = chan->ch_vmbus;
 	struct vmbus_msghc *mh;
 	struct vmbus_chanmsg_chclose *req;
+	uint32_t old_stflags;
 	int error;
 
-	/* TODO: stringent check */
-	atomic_clear_int(&chan->ch_stflags, VMBUS_CHAN_ST_OPENED);
+	/*
+	 * NOTE:
+	 * Sub-channels are closed upon their primary channel closing,
+	 * so they can be closed even before they are opened.
+	 */
+	for (;;) {
+		old_stflags = chan->ch_stflags;
+		if (atomic_cmpset_int(&chan->ch_stflags, old_stflags,
+		    old_stflags & ~VMBUS_CHAN_ST_OPENED))
+			break;
+	}
+	if ((old_stflags & VMBUS_CHAN_ST_OPENED) == 0) {
+		/* Not opened yet; done */
+		if (bootverbose) {
+			vmbus_chan_printf(chan, "chan%u not opened\n",
+			    chan->ch_id);
+		}
+		return;
+	}
 
 	/*
 	 * Free this channel's sysctl tree attached to its device's