package/kernel/mac80211/patches/329-ath9k-unlock-rcu-read-when-returning-early.patch

   1 From: Tobias Klausmann <tobias.johannes.klausmann@mni.thm.de>
   2 Date: Mon, 12 Dec 2016 19:50:01 +0100
   3 Subject: [PATCH] ath9k: unlock rcu read when returning early
   4
   5 Starting with ath9k: use ieee80211_tx_status_noskb where possible
   6 [d94a461d7a7df68991fb9663531173f60ef89c68] the driver uses rcu_read_lock() &&
   7 rcu_read_unlock() yet on returning early in ath_tx_edma_tasklet() the unlock is
   8 missing leading to stalls and suspicious RCU usage:
   9
  10  ===============================
  11  [ INFO: suspicious RCU usage. ]
  12  4.9.0-rc8 #11 Not tainted
  13  -------------------------------
  14  kernel/rcu/tree.c:705 Illegal idle entry in RCU read-side critical section.!
  15
  16  other info that might help us debug this:
  17
  18  RCU used illegally from idle CPU!
  19  rcu_scheduler_active = 1, debug_locks = 0
  20  RCU used illegally from extended quiescent state!
  21  1 lock held by swapper/7/0:
  22  #0:
  23   (
  24  rcu_read_lock
  25  ){......}
  26  , at:
  27  [<ffffffffa06ed110>] ath_tx_edma_tasklet+0x0/0x450 [ath9k]
  28
  29  stack backtrace:
  30  CPU: 7 PID: 0 Comm: swapper/7 Not tainted 4.9.0-rc8 #11
  31  Hardware name: Acer Aspire V3-571G/VA50_HC_CR, BIOS V2.21 12/16/2013
  32   ffff88025efc3f38 ffffffff8132b1e5 ffff88017ede4540 0000000000000001
  33   ffff88025efc3f68 ffffffff810a25f7 ffff88025efcee60 ffff88017edebdd8
  34   ffff88025eeb5400 0000000000000091 ffff88025efc3f88 ffffffff810c3cd4
  35  Call Trace:
  36   <IRQ>
  37   [<ffffffff8132b1e5>] dump_stack+0x68/0x93
  38   [<ffffffff810a25f7>] lockdep_rcu_suspicious+0xd7/0x110
  39   [<ffffffff810c3cd4>] rcu_eqs_enter_common.constprop.85+0x154/0x200
  40   [<ffffffff810c5a54>] rcu_irq_exit+0x44/0xa0
  41   [<ffffffff81058631>] irq_exit+0x61/0xd0
  42   [<ffffffff81018d25>] do_IRQ+0x65/0x110
  43   [<ffffffff81672189>] common_interrupt+0x89/0x89
  44   <EOI>
  45   [<ffffffff814ffe11>] ? cpuidle_enter_state+0x151/0x200
  46   [<ffffffff814ffee2>] cpuidle_enter+0x12/0x20
  47   [<ffffffff8109a6ae>] call_cpuidle+0x1e/0x40
  48   [<ffffffff8109a8f6>] cpu_startup_entry+0x146/0x220
  49   [<ffffffff810336f8>] start_secondary+0x148/0x170
  50
  51 Signed-off-by: Tobias Klausmann <tobias.johannes.klausmann@mni.thm.de>
  52 Signed-off-by: Felix Fietkau <nbd@nbd.name>
  53 ---
  54
  55 --- a/drivers/net/wireless/ath/ath9k/xmit.c
  56 +++ b/drivers/net/wireless/ath/ath9k/xmit.c
  57 @@ -2757,7 +2757,7 @@ void ath_tx_edma_tasklet(struct ath_soft
  58                 fifo_list = &txq->txq_fifo[txq->txq_tailidx];
  59                 if (list_empty(fifo_list)) {
  60                         ath_txq_unlock(sc, txq);
  61 -                       return;
  62 +                       break;
  63                 }
  64
  65                 bf = list_first_entry(fifo_list, struct ath_buf, list);