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From: Greg KH on 6 Aug 2010 15:10
2.6.32-stable review patch. If anyone has any objections, please let us know.

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

From: Stanislaw Gruszka <sgruszka(a)redhat.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(a)redhat.com>
Signed-off-by: John W. Linville <linville(a)tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh(a)suse.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
@@ -497,11 +497,10 @@ 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);
@@ -797,12 +796,11 @@ 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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