iwlwifi: do not cancel delayed work inside spin_lock_irqsave
Calling cancel_delayed_work() from inside
spin_lock_irqsave, introduces a potential deadlock.
As explained by Johannes Berg <johannes@sipsolutions.net>
A - lock
T - timer
phase CPU 1 CPU 2
---------------------------------------------
some place that calls
cancel_timer_sync()
(which is the | code)
lock-irq(A)
| "lock-irq"(T)
| "unlock"(T)
| wait(T)
unlock(A)
timer softirq
"lock"(T)
run(T)
"unlock"(T)
irq handler
lock(A)
unlock(A)
Now all that again, interleaved, leading to deadlock:
lock-irq(A)
"lock"(T)
run(T)
IRQ during or maybe
before run(T) --> lock(A)
"lock-irq"(T)
wait(T)
We fix this by moving the call to cancel_delayed_work() into workqueue.
There are cases where the work may not actually be queued or running
at the time we are trying to cancel it, but cancel_delayed_work() is
able to deal with this.
Also cleanup iwl_set_mode related to this call. This function
(iwl_set_mode) is only called when bringing interface up and there will
thus not be any scanning done. No need to try to cancel scanning.
Fixes http://bugzilla.kernel.org/show_bug.cgi?id=13224, which was also
reported at http://marc.info/?l=linux-wireless&m=124081921903223&w=2 .
Tested-by: Miles Lane <miles.lane@gmail.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Acked-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/iwlwifi/iwl-scan.c b/drivers/net/wireless/iwlwifi/iwl-scan.c
index e7c65c4..6330b91 100644
--- a/drivers/net/wireless/iwlwifi/iwl-scan.c
+++ b/drivers/net/wireless/iwlwifi/iwl-scan.c
@@ -227,9 +227,6 @@
/* The HW is no longer scanning */
clear_bit(STATUS_SCAN_HW, &priv->status);
- /* The scan completion notification came in, so kill that timer... */
- cancel_delayed_work(&priv->scan_check);
-
IWL_DEBUG_INFO(priv, "Scan pass on %sGHz took %dms\n",
(priv->scan_bands & BIT(IEEE80211_BAND_2GHZ)) ?
"2.4" : "5.2",
@@ -712,6 +709,8 @@
mutex_lock(&priv->mutex);
+ cancel_delayed_work(&priv->scan_check);
+
if (!iwl_is_ready(priv)) {
IWL_WARN(priv, "request scan called when driver not ready.\n");
goto done;
@@ -925,6 +924,8 @@
IWL_DEBUG_SCAN(priv, "SCAN complete scan\n");
+ cancel_delayed_work(&priv->scan_check);
+
ieee80211_scan_completed(priv->hw, false);
if (test_bit(STATUS_EXIT_PENDING, &priv->status))