From d1f1c0e289e1bc46cd6873ba6dd6c627f459e7fa Mon Sep 17 00:00:00 2001 From: Tobias Klausmann Date: Tue, 13 Dec 2016 18:08:07 +0100 Subject: [PATCH] ath9k: do not return early to fix rcu unlocking Starting with commit d94a461d7a7d ("ath9k: use ieee80211_tx_status_noskb where possible") 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: [] 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: [] dump_stack+0x68/0x93 [] lockdep_rcu_suspicious+0xd7/0x110 [] rcu_eqs_enter_common.constprop.85+0x154/0x200 [] rcu_irq_exit+0x44/0xa0 [] irq_exit+0x61/0xd0 [] do_IRQ+0x65/0x110 [] common_interrupt+0x89/0x89 [] ? cpuidle_enter_state+0x151/0x200 [] cpuidle_enter+0x12/0x20 [] call_cpuidle+0x1e/0x40 [] cpu_startup_entry+0x146/0x220 [] start_secondary+0x148/0x170 Signed-off-by: Tobias Klausmann Fixes: d94a461d7a7d ("ath9k: use ieee80211_tx_status_noskb where possible") Cc: # v4.9 Acked-by: Felix Fietkau Acked-by: Paul E. McKenney Tested-by: Gabriel Craciunescu Signed-off-by: Kalle Valo --- drivers/net/wireless/ath/ath9k/xmit.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/wireless/ath/ath9k/xmit.c b/drivers/net/wireless/ath/ath9k/xmit.c index 486afa98a5b8d1..4e2f3ac266c375 100644 --- a/drivers/net/wireless/ath/ath9k/xmit.c +++ b/drivers/net/wireless/ath/ath9k/xmit.c @@ -2713,7 +2713,7 @@ 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); - return; + break; } bf = list_first_entry(fifo_list, struct ath_buf, list);