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From c342834cd315ac5c7c326c022e467a876fadd70d Mon Sep 17 00:00:00 2001
From: Sasha Levin <sashal@kernel.org>
Date: Tue, 22 Dec 2020 14:34:47 +0800
Subject: ath10k: fix wmi mgmt tx queue full due to race condition
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From: Miaoqing Pan <miaoqing@codeaurora.org>
[ Upstream commit b55379e343a3472c35f4a1245906db5158cab453 ]
Failed to transmit wmi management frames:
[84977.840894] ath10k_snoc a000000.wifi: wmi mgmt tx queue is full
[84977.840913] ath10k_snoc a000000.wifi: failed to transmit packet, dropping: -28
[84977.840924] ath10k_snoc a000000.wifi: failed to submit frame: -28
[84977.840932] ath10k_snoc a000000.wifi: failed to transmit frame: -28
This issue is caused by race condition between skb_dequeue and
__skb_queue_tail. The queue of wmi_mgmt_tx_queue is protected by a
different lock: ar->data_lock vs list->lock, the result is no protection.
So when ath10k_mgmt_over_wmi_tx_work() and ath10k_mac_tx_wmi_mgmt()
running concurrently on different CPUs, there appear to be a rare corner
cases when the queue length is 1,
CPUx (skb_deuque) CPUy (__skb_queue_tail)
next=list
prev=list
struct sk_buff *skb = skb_peek(list); WRITE_ONCE(newsk->next, next);
WRITE_ONCE(list->qlen, list->qlen - 1);WRITE_ONCE(newsk->prev, prev);
next = skb->next; WRITE_ONCE(next->prev, newsk);
prev = skb->prev; WRITE_ONCE(prev->next, newsk);
skb->next = skb->prev = NULL; list->qlen++;
WRITE_ONCE(next->prev, prev);
WRITE_ONCE(prev->next, next);
If the instruction next = skb->next is executed before
WRITE_ONCE(prev->next, newsk)’, newsk will be lost, as CPUx get the
old next pointer, but the length is still added by one. The final
result is the length of the queue will reach the maximum value but
the queue is empty.
So remove ar->data_lock, and use 'skb_queue_tail' instead of
'__skb_queue_tail' to prevent the potential race condition. Also switch
to use skb_queue_len_lockless, in case we queue a few SKBs simultaneously.
Tested-on: WCN3990 hw1.0 SNOC WLAN.HL.3.1.c2-00033-QCAHLSWMTPLZ-1
Signed-off-by: Miaoqing Pan <miaoqing@codeaurora.org>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/1608618887-8857-1-git-send-email-miaoqing@codeaurora.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/wireless/ath/ath10k/mac.c | 15 ++++-----------
1 file changed, 4 insertions(+), 11 deletions(-)
diff --git a/drivers/net/wireless/ath/ath10k/mac.c b/drivers/net/wireless/ath/ath10k/mac.c
index e815aab412d7..9a56a0a5f85d 100644
--- a/drivers/net/wireless/ath/ath10k/mac.c
+++ b/drivers/net/wireless/ath/ath10k/mac.c
@@ -3763,23 +3763,16 @@ bool ath10k_mac_tx_frm_has_freq(struct ath10k *ar)
static int ath10k_mac_tx_wmi_mgmt(struct ath10k *ar, struct sk_buff *skb)
{
struct sk_buff_head *q = &ar->wmi_mgmt_tx_queue;
- int ret = 0;
-
- spin_lock_bh(&ar->data_lock);
- if (skb_queue_len(q) == ATH10K_MAX_NUM_MGMT_PENDING) {
+ if (skb_queue_len_lockless(q) >= ATH10K_MAX_NUM_MGMT_PENDING) {
ath10k_warn(ar, "wmi mgmt tx queue is full\n");
- ret = -ENOSPC;
- goto unlock;
+ return -ENOSPC;
}
- __skb_queue_tail(q, skb);
+ skb_queue_tail(q, skb);
ieee80211_queue_work(ar->hw, &ar->wmi_mgmt_tx_work);
-unlock:
- spin_unlock_bh(&ar->data_lock);
-
- return ret;
+ return 0;
}
static enum ath10k_mac_tx_path
--
2.30.1