On 13.12.2016 11:41, Felix Fietkau wrote:
On 2016-12-12 19:50, Tobias Klausmann wrote:Starting with ath9k: use ieee80211_tx_status_noskb where possible [d94a461d7a7df68991fb9663531173f60ef89c68] the driver uses rcu_read_lock() && rcu_read_unlock() yet on returning early in ath_tx_edma_tasklet() the unlock is missing leading to stalls and suspicious RCU usage: =============================== [ INFO: suspicious RCU usage. ] 4.9.0-rc8 #11 Not tainted ------------------------------- kernel/rcu/tree.c:705 Illegal idle entry in RCU read-side critical section.! other info that might help us debug this: RCU used illegally from idle CPU! rcu_scheduler_active = 1, debug_locks = 0 RCU used illegally from extended quiescent state! 1 lock held by swapper/7/0: #0: ( rcu_read_lock ){......} , at: [<ffffffffa06ed110>] ath_tx_edma_tasklet+0x0/0x450 [ath9k] stack backtrace: CPU: 7 PID: 0 Comm: swapper/7 Not tainted 4.9.0-rc8 #11 Hardware name: Acer Aspire V3-571G/VA50_HC_CR, BIOS V2.21 12/16/2013 ffff88025efc3f38 ffffffff8132b1e5 ffff88017ede4540 0000000000000001 ffff88025efc3f68 ffffffff810a25f7 ffff88025efcee60 ffff88017edebdd8 ffff88025eeb5400 0000000000000091 ffff88025efc3f88 ffffffff810c3cd4 Call Trace: <IRQ> [<ffffffff8132b1e5>] dump_stack+0x68/0x93 [<ffffffff810a25f7>] lockdep_rcu_suspicious+0xd7/0x110 [<ffffffff810c3cd4>] rcu_eqs_enter_common.constprop.85+0x154/0x200 [<ffffffff810c5a54>] rcu_irq_exit+0x44/0xa0 [<ffffffff81058631>] irq_exit+0x61/0xd0 [<ffffffff81018d25>] do_IRQ+0x65/0x110 [<ffffffff81672189>] common_interrupt+0x89/0x89 <EOI> [<ffffffff814ffe11>] ? cpuidle_enter_state+0x151/0x200 [<ffffffff814ffee2>] cpuidle_enter+0x12/0x20 [<ffffffff8109a6ae>] call_cpuidle+0x1e/0x40 [<ffffffff8109a8f6>] cpu_startup_entry+0x146/0x220 [<ffffffff810336f8>] start_secondary+0x148/0x170 Signed-off-by: Tobias Klausmann <tobias.johannes.klausmann@xxxxxxxxxx> --- drivers/net/wireless/ath/ath9k/xmit.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/net/wireless/ath/ath9k/xmit.c b/drivers/net/wireless/ath/ath9k/xmit.c index 52bfbb988611..857d5ae09a1d 100644 --- a/drivers/net/wireless/ath/ath9k/xmit.c +++ b/drivers/net/wireless/ath/ath9k/xmit.c @@ -2787,6 +2787,7 @@ void ath_tx_edma_tasklet(struct ath_softc *sc) fifo_list = &txq->txq_fifo[txq->txq_tailidx]; if (list_empty(fifo_list)) { ath_txq_unlock(sc, txq); + rcu_read_unlock();Technically this is fine as well, but I'd prefer a fix where you replace the 'return' with 'break', thus avoiding the duplication of rcu_read_unlock()
Actually if you want to avoid it, maybe skipping over the rest is better (as originally intended):
... ath_txq_unlock(sc, txq); goto unlock; } ... unlock: rcu_read_unlock(); Thanks, Tobias
Thanks, - Felix
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