Hi Thomas, Thanks for your response. On Fri, Sep 3, 2021 at 5:07 AM Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote: > Looked once more at the trace output. It seems to be incomplete. The > last recording of softirq raise was at 379568us ~= 0.38s post boot, but > the splat comes about 20 seconds post boot. Did your kernel trigger a > WARN_ON before that splat? If so, that might have disabled tracing. You are right. The WARN_ON only happens after hostapd runs, which is at a much later stage. > As you are triggering this manually by invoking hostapd and the machine > should be still functional afterwards, can you please replace Paul's > debug patch with the one below? Please remove the command line option > and do the following: > > # echo 1 >/sys/kernel/debug/tracing/events/irq/softirq_raise/enable > # echo 1 >/sys/kernel/debug/tracing/events/irq/softirq_entry/enable > # echo 1 > /proc/sys/kernel/stack_tracer_enabled > # hostapd ... > > Once the warning triggered do: > > # cat /sys/kernel/debug/tracing/trace >trace.txt > > That should give us the full trace data and hopefully a better > understanding of the problem. I did as suggested and here is trace.txt: https://pastebin.com/VUfLRJ8a Also, while investigating this problem I saw a commit that fixed a similar issue: e63052a5dd3c ("mlx5e: add add missing BH locking around napi_schdule()"). I then tried the same approach on the ath10k sdio driver: diff --git a/drivers/net/wireless/ath/ath10k/sdio.c b/drivers/net/wireless/ath/ath10k/sdio.c index b746052737e0..eb705214f3f0 100644 --- a/drivers/net/wireless/ath/ath10k/sdio.c +++ b/drivers/net/wireless/ath/ath10k/sdio.c @@ -1363,8 +1363,11 @@ static void ath10k_rx_indication_async_work(struct work_struct *work) ep->ep_ops.ep_rx_complete(ar, skb); } - if (test_bit(ATH10K_FLAG_CORE_REGISTERED, &ar->dev_flags)) + if (test_bit(ATH10K_FLAG_CORE_REGISTERED, &ar->dev_flags)) { + local_bh_disable(); napi_schedule(&ar->napi); + local_bh_enable(); + } } and no longer get the "NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!!" error messages after launching hostapd. Is this a proper fix? Thanks, Fabio Estevam
