On 2016-12-13 18:08, Tobias Klausmann wrote:
> 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:
> [<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>
> Fixes: d94a461d7a7d ("ath9k: use ieee80211_tx_status_noskb where possible")
> Cc: <stable@xxxxxxxxxxxxxxx> # v4.9
Acked-by: Felix Fietkau <nbd@xxxxxxxx>
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