diff mbox series

[07/24] mac80211: document RCU requirements for ieee80211_tx_dequeue()

Message ID 20181215090325.31604-8-luca@coelho.fi (mailing list archive)
State Accepted
Delegated to: Johannes Berg
Headers show
Series cfg80211/mac80211 patches from our internal tree 2018-12-15 | expand

Commit Message

Luca Coelho Dec. 15, 2018, 9:03 a.m. UTC 
From: Johannes Berg <johannes.berg@intel.com>

In the iwlwifi conversion, we sometimes call this from outside
of the wake_tx_queue() method, and in those cases must be in an
RCU critical section. Document this requirement.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
---
 include/net/mac80211.h | 8 ++++++++
 1 file changed, 8 insertions(+)
diff mbox series

Patch

diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 1553152b77e0..40ad390f0f6a 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -6106,6 +6106,14 @@  void ieee80211_unreserve_tid(struct ieee80211_sta *sta, u8 tid);
  * @txq: pointer obtained from station or virtual interface
  *
  * Returns the skb if successful, %NULL if no frame was available.
+ *
+ * Note that this must be called in an rcu_read_lock() critical section,
+ * which can only be released after the SKB was handled. Some pointers in
+ * skb->cb, e.g. the key pointer, are protected by by RCU and thus the
+ * critical section must persist not just for the duration of this call
+ * but for the duration of the frame handling.
+ * However, also note that while in the wake_tx_queue() method,
+ * rcu_read_lock() is already held.
  */
 struct sk_buff *ieee80211_tx_dequeue(struct ieee80211_hw *hw,
 				     struct ieee80211_txq *txq);