mac80211: document ieee80211_rx() context requirement

ieee80211_rx() must be called with softirqs disabled since the networking stack requires this for netif_rx() and some code in mac80211 can assume that it can not be processing its own tasklet and this call at the same time. It may be possible to remove this requirement after a careful audit of mac80211 and doing any needed locking improvements in it along with disabling softirqs around netif_rx(). An alternative might be to push all packet processing to process context in mac80211, instead of to the tasklet, and add other synchronisation. Signed-off-by: Johannes Berg <johannes@sipsolutions.net> Signed-off-by: John W. Linville <linville@tuxdriver.com>

mac80211: document ieee80211_rx() context requirement
ieee80211_rx() must be called with softirqs disabled since the networking stack requires this for netif_rx() and some code in mac80211 can assume that it can not be processing its own tasklet and this call at the same time. It may be possible to remove this requirement after a careful audit of mac80211 and doing any needed locking improvements in it along with disabling softirqs around netif_rx(). An alternative might be to push all packet processing to process context in mac80211, instead of to the tasklet, and add other synchronisation. Signed-off-by: Johannes Berg <johannes@sipsolutions.net> Signed-off-by: John W. Linville <linville@tuxdriver.com>
Johannes Berg · John W. Linville · Eric Lee · Eric Lee · Eric Lee · Eric Lee
1 parent edbfdcceb4
Showing 2 changed files with 4 additions and 0 deletions Side-by-side Diff
include/net/mac80211.h
net/mac80211/rx.c
@@ -1669,6 +1669,8 @@
  * to this function and ieee80211_rx_irqsafe() may not be mixed for a
  * single hardware.
  *
+ * Note that right now, this function must be called with softirqs disabled.
+ *
  * @hw: the hardware this frame came in on
  * @skb: the buffer to receive, owned by mac80211 after this call
  */
@@ -2453,6 +2453,8 @@
 	struct ieee80211_supported_band *sband;
 	struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
  
+	WARN_ON_ONCE(softirq_count() == 0);
+
 	if (WARN_ON(status->band < 0 ||
 		    status->band >= IEEE80211_NUM_BANDS))
 		goto drop;
...	...	@@ -1669,6 +1669,8 @@
1669	1669	* to this function and ieee80211_rx_irqsafe() may not be mixed for a
1670	1670	* single hardware.
1671	1671	*
	1672	+ * Note that right now, this function must be called with softirqs disabled.
	1673	+ *
1672	1674	* @hw: the hardware this frame came in on
1673	1675	* @skb: the buffer to receive, owned by mac80211 after this call
1674	1676	*/
...	...	@@ -2453,6 +2453,8 @@
2453	2453	struct ieee80211_supported_band *sband;
2454	2454	struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
2455	2455
	2456	+ WARN_ON_ONCE(softirq_count() == 0);
	2457	+
2456	2458	if (WARN_ON(status->band < 0 \|\|
2457	2459	status->band >= IEEE80211_NUM_BANDS))
2458	2460	goto drop;