On 04/11/2012 10:31 PM, Johannes Berg wrote:
On Mon, 2012-04-09 at 22:19 -0500, Larry Finger wrote:When running kernel 3.4-rc2 from wireless testing, I got the following logged: [ 2299.344437] =============================== [ 2299.344443] [ INFO: suspicious RCU usage. ] [ 2299.344452] 3.4.0-rc2-wl+ #222 Not tainted [ 2299.344458] ------------------------------- [ 2299.344466] net/mac80211/sta_info.h:449 suspicious rcu_dereference_protected() usage! [ 2299.344472] [ 2299.344474] other info that might help us debug this: [ 2299.344477] [ 2299.344484] [ 2299.344486] rcu_scheduler_active = 1, debug_locks = 0 [ 2299.344493] 1 lock held by swapper/1/0: [ 2299.344499] #0: (&tid_tx->session_timer){+.-...}, at: [<ffffffff8104850a>] run_timer_softirq+0xfa/0x6e0 [ 2299.344533] [ 2299.344535] stack backtrace: [ 2299.344544] Pid: 0, comm: swapper/1 Not tainted 3.4.0-rc2-wl+ #222 [ 2299.344551] Call Trace: [ 2299.344557]<IRQ> [<ffffffff81092fdd>] lockdep_rcu_suspicious+0xfd/0x130 [ 2299.344651] [<ffffffffa05db673>] sta_tx_agg_session_timer_expired+0xe3/0x100 [mac80211]That's odd: static inline struct tid_ampdu_tx * rcu_dereference_protected_tid_tx(struct sta_info *sta, int tid) { return rcu_dereference_protected(sta->ampdu_mlme.tid_tx[tid], lockdep_is_held(&sta->lock) || lockdep_is_held(&sta->ampdu_mlme.mtx)); } sta_tx_agg_session_timer_expired calls ieee80211_stop_tx_ba_session which does: spin_lock_bh(&sta->lock); tid_tx = rcu_dereference_protected_tid_tx(sta, tid); So why would the message happen? Strange.
When I first saw the thread at http://lkml.indiana.edu/hypermail/linux/kernel/1204.1/01446.html, I thought it might be about the same problem, but that appears to be restricted to sparc64.
The problem does not happen every time - even more strangeness. Larry -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
