cfg80211: make cfg80211_sched_scan_results() work from atomic context

Arend Van Spriel · jmberg-intel · commit 1b57b6210f4e · 2017-05-23T14:36:46.000+02:00
Drivers should be able to call cfg80211_sched_scan_results() from atomic context. However, with the introduction of multiple scheduled scan feature this requirement was not taken into account resulting in regression shown below. [ 119.021594] BUG: scheduling while atomic: irq/47-iwlwifi/517/0x00000200 [ 119.021604] Modules linked in: [...] [ 119.021759] CPU: 1 PID: 517 Comm: irq/47-iwlwifi Not tainted 4.12.0-rc2-t440s-20170522+ #1 [ 119.021763] Hardware name: LENOVO 20AQS03H00/20AQS03H00, BIOS GJET91WW (2.41 ) 09/21/2016 [ 119.021766] Call Trace: [ 119.021778] ? dump_stack+0x5c/0x84 [ 119.021784] ? __schedule_bug+0x4c/0x70 [ 119.021792] ? __schedule+0x496/0x5c0 [ 119.021798] ? schedule+0x2d/0x80 [ 119.021804] ? schedule_preempt_disabled+0x5/0x10 [ 119.021810] ? __mutex_lock.isra.0+0x18e/0x4c0 [ 119.021817] ? __wake_up+0x2f/0x50 [ 119.021833] ? cfg80211_sched_scan_results+0x19/0x60 [cfg80211] [ 119.021844] ? cfg80211_sched_scan_results+0x19/0x60 [cfg80211] [ 119.021859] ? iwl_mvm_rx_lmac_scan_iter_complete_notif+0x17/0x30 [iwlmvm] [ 119.021869] ? iwl_pcie_rx_handle+0x2a9/0x7e0 [iwlwifi] [ 119.021878] ? iwl_pcie_irq_handler+0x17c/0x730 [iwlwifi] [ 119.021884] ? irq_forced_thread_fn+0x60/0x60 [ 119.021887] ? irq_thread_fn+0x16/0x40 [ 119.021892] ? irq_thread+0x109/0x180 [ 119.021896] ? wake_threads_waitq+0x30/0x30 [ 119.021901] ? kthread+0xf2/0x130 [ 119.021905] ? irq_thread_dtor+0x90/0x90 [ 119.021910] ? kthread_create_on_node+0x40/0x40 [ 119.021915] ? ret_from_fork+0x26/0x40 Fixes: b34939b ("cfg80211: add request id to cfg80211_sched_scan_*() api") Reported-by: Sander Eikelenboom <linux@eikelenboom.it> Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com> Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/wireless/scan.c b/net/wireless/scan.c
@@ -322,9 +322,9 @@ cfg80211_find_sched_scan_req(struct cfg80211_registered_device *rdev, u64 reqid)
 {
 	struct cfg80211_sched_scan_request *pos;
 
-	ASSERT_RTNL();
+	WARN_ON_ONCE(!rcu_read_lock_held() && !lockdep_rtnl_is_held());
 
-	list_for_each_entry(pos, &rdev->sched_scan_req_list, list) {
+	list_for_each_entry_rcu(pos, &rdev->sched_scan_req_list, list) {
 		if (pos->reqid == reqid)
 			return pos;
 	}
@@ -398,13 +398,13 @@ void cfg80211_sched_scan_results(struct wiphy *wiphy, u64 reqid)
 	trace_cfg80211_sched_scan_results(wiphy, reqid);
 	/* ignore if we're not scanning */
 
-	rtnl_lock();
+	rcu_read_lock();
 	request = cfg80211_find_sched_scan_req(rdev, reqid);
 	if (request) {
 		request->report_results = true;
 		queue_work(cfg80211_wq, &rdev->sched_scan_res_wk);
 	}
-	rtnl_unlock();
+	rcu_read_unlock();
 }
 EXPORT_SYMBOL(cfg80211_sched_scan_results);
 

Original file line number	Diff line number	Diff line change
`@@ -322,9 +322,9 @@ cfg80211_find_sched_scan_req(struct cfg80211_registered_device *rdev, u64 reqid)`
`322`	`322`	`{`
`323`	`323`	`struct cfg80211_sched_scan_request *pos;`
`324`	`324`
`325`		`- ASSERT_RTNL();`
	`325`	`+ WARN_ON_ONCE(!rcu_read_lock_held() && !lockdep_rtnl_is_held());`
`326`	`326`
`327`		`- list_for_each_entry(pos, &rdev->sched_scan_req_list, list) {`
	`327`	`+ list_for_each_entry_rcu(pos, &rdev->sched_scan_req_list, list) {`
`328`	`328`	`if (pos->reqid == reqid)`
`329`	`329`	`return pos;`
`330`	`330`	`}`
`@@ -398,13 +398,13 @@ void cfg80211_sched_scan_results(struct wiphy *wiphy, u64 reqid)`
`398`	`398`	`trace_cfg80211_sched_scan_results(wiphy, reqid);`
`399`	`399`	`/* ignore if we're not scanning */`
`400`	`400`
`401`		`- rtnl_lock();`
	`401`	`+ rcu_read_lock();`
`402`	`402`	`request = cfg80211_find_sched_scan_req(rdev, reqid);`
`403`	`403`	`if (request) {`
`404`	`404`	`request->report_results = true;`
`405`	`405`	`queue_work(cfg80211_wq, &rdev->sched_scan_res_wk);`
`406`	`406`	`}`
`407`		`- rtnl_unlock();`
	`407`	`+ rcu_read_unlock();`
`408`	`408`	`}`
`409`	`409`	`EXPORT_SYMBOL(cfg80211_sched_scan_results);`
`410`	`410`