PM code has a watchdog to trigger a BUG when suspend callback
is not returning in several seconds. Some WLAN hardware has
longer timeouts for non-interruptible configuration-related
operations, leading to the watchdog timeout while
ieee80211_scan_cancel is waiting on a mutex.
The patch checks if interface mutex is already held and rejects
suspend if there is a possibility of locking.
---
net/mac80211/pm.c | 19 +++++++++++++++++++
1 files changed, 19 insertions(+), 0 deletions(-)
diff --git a/net/mac80211/pm.c b/net/mac80211/pm.c
index 9ee7164..468d2e5 100644
--- a/net/mac80211/pm.c
+++ b/net/mac80211/pm.c
@@ -37,6 +37,25 @@ int __ieee80211_suspend(struct ieee80211_hw *hw,
struct cfg80211_wowlan *wowlan)
if (!local->open_count)
goto suspend;
+ /* PM code has a watchdog to trigger a BUG when
+ * suspend callback is not returning in several seconds.
+ * Some WLAN hardware has longer timeouts for non-interruptible
+ * configuration-related operations, leading to the watchdog
+ * timeout while ieee80211_scan_cancel is waiting on the mutex.
+ *
+ * The code below checks if interface mutex is already held
+ * and rejects suspend if there is a possibility of locking.
+ *
+ * It's a bit racy, but handles most of cases.
+ */
+ if (mutex_trylock(&local->mtx))
+ mutex_unlock(&local->mtx);
+ else {
+ wiphy_warn(hw->wiphy, "Suspend when operation "
+ "is in progress. Suspend aborted.\n");
+ return -EBUSY;
+ }
+
ieee80211_scan_cancel(local);
if (hw->flags & IEEE80211_HW_AMPDU_AGGREGATION) {
--
1.7.1
--
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