linux-kernel - [20/36] iwlwifi: fix scan abort

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Date:	Fri, 06 Aug 2010 12:20:01 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Stanislaw Gruszka <sgruszka@...hat.com>,
	"John W. Linville" <linville@...driver.com>
Subject: [20/36] iwlwifi: fix scan abort

2.6.34-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Stanislaw Gruszka <sgruszka@...hat.com>

commit d28232b461b8d54b09e59325dbac8b0913ce2049 upstream.

Fix possible double priv->mutex lock introduced by commit
a69b03e941abae00380fc6bc1877fb797a1b31e6
"iwlwifi: cancel scan watchdog in iwl_bg_abort_scan" .
We can not call cancel_delayed_work_sync(&priv->scan_check) with
priv->mutex locked because workqueue function iwl_bg_scan_check()
take that lock internally.

We do not need to synchronize when canceling priv->scan_check work.
We can avoid races (sending double abort command or send no
command at all) using STATUS_SCAN_ABORT bit. Moreover
current iwl_bg_scan_check() code seems to be broken, as
we should not send abort commands when currently aborting.

Signed-off-by: Stanislaw Gruszka <sgruszka@...hat.com>
Signed-off-by: John W. Linville <linville@...driver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 drivers/net/wireless/iwlwifi/iwl-scan.c |   18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

--- a/drivers/net/wireless/iwlwifi/iwl-scan.c
+++ b/drivers/net/wireless/iwlwifi/iwl-scan.c
@@ -607,11 +607,10 @@ void iwl_bg_scan_check(struct work_struc
 		return;
 
 	mutex_lock(&priv->mutex);
-	if (test_bit(STATUS_SCANNING, &priv->status) ||
-	    test_bit(STATUS_SCAN_ABORTING, &priv->status)) {
-		IWL_DEBUG_SCAN(priv, "Scan completion watchdog resetting "
-			"adapter (%dms)\n",
-			jiffies_to_msecs(IWL_SCAN_CHECK_WATCHDOG));
+	if (test_bit(STATUS_SCANNING, &priv->status) &&
+	    !test_bit(STATUS_SCAN_ABORTING, &priv->status)) {
+		IWL_DEBUG_SCAN(priv, "Scan completion watchdog (%dms)\n",
+			       jiffies_to_msecs(IWL_SCAN_CHECK_WATCHDOG));
 
 		if (!test_bit(STATUS_EXIT_PENDING, &priv->status))
 			iwl_send_scan_abort(priv);
@@ -950,12 +949,11 @@ void iwl_bg_abort_scan(struct work_struc
 	    !test_bit(STATUS_GEO_CONFIGURED, &priv->status))
 		return;
 
-	mutex_lock(&priv->mutex);
-
-	cancel_delayed_work_sync(&priv->scan_check);
-	set_bit(STATUS_SCAN_ABORTING, &priv->status);
-	iwl_send_scan_abort(priv);
+	cancel_delayed_work(&priv->scan_check);
 
+	mutex_lock(&priv->mutex);
+	if (test_bit(STATUS_SCAN_ABORTING, &priv->status))
+		iwl_send_scan_abort(priv);
 	mutex_unlock(&priv->mutex);
 }
 EXPORT_SYMBOL(iwl_bg_abort_scan);


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