| Message ID | 20230809073432.4193-1-johan+linaro@kernel.org |
|---|---|
| State | New |
| Headers | show |
| Series | Revert "Revert "wifi: ath11k: Enable threaded NAPI"" | expand |
On Thu, Aug 10, 2023 at 10:03:55AM +0530, Manikanta Pubbisetty wrote: > On 8/9/2023 2:46 PM, Johan Hovold wrote: > > On Wed, Aug 09, 2023 at 02:32:37PM +0530, Manikanta Pubbisetty wrote: > > > On 8/9/2023 1:04 PM, Johan Hovold wrote: > > > > This reverts commit d265ebe41c911314bd273c218a37088835959fa1. > > > > > > > > Disabling threaded NAPI causes the Lenovo ThinkPad X13s to hang (e.g. no > > > > more interrupts received) almost immediately during RX. > > > > > > > > Apparently something broke since commit 13aa2fb692d3 ("wifi: ath11k: > > > > Enable threaded NAPI") so that a simple revert is no longer possible. > > > What is the chip that Lenovo Thinkpad X13s is having? > > > > It's a WCN6855 (QCNFA765). > > WCN6855 & QCN9074 share the same driver code base since both being PCIe > devices. One working and another not working seems to be surprising. Do you > have a dmesg log when this problem occurred? I can't access the logs after I hit this bug (e.g. as there are no interrupts received from the keyboard) but when I trigger this from the console, there is nothing logged when the hang happens. Later, secondary errors are logged from other drivers that are no longer receiving interrupts either, and RCU detects a stall as I mentioned elsewhere. Johan
On Thu, Aug 10, 2023 at 10:16:21AM +0530, Manikanta Pubbisetty wrote: > Also it is worth to give a try with this patch here https://patchwork.kernel.org/project/linux-wireless/patch/20230601033840.2997-1-quic_bqiang@quicinc.com/ > . This seems to be fixing some known interrupt issue on WCN6855. Could you > pls give a try? That patch makes no difference as the X13s use multiple MSIs (so ath11k_pci_set_irq_affinity_hint() is a noop). Johan
Hi Kalle, On Wed, Aug 09, 2023 at 09:34:32AM +0200, Johan Hovold wrote: > Disabling threaded NAPI caused a severe regression in 6.5-rc5 by making > the X13s completely unusable (e.g. no keyboard input, I've seen an RCU > splat once). > > I'm supposed to be on holiday this week, but thanks to the rain I gave > rc5 a try and ran into this. > > I've added Bjorn, Mani and Konrad on CC who may be able to help with > debugging this further if needed while I'm out-of-office. Back from my holiday now, and this regression is still there with 6.5-rc7. Any chance we can get the offending commit reverted before 6.5 is released? I'll take a closer look at this meanwhile. Johan
Johan Hovold <johan@kernel.org> writes: > Hi Kalle, > > On Wed, Aug 09, 2023 at 09:34:32AM +0200, Johan Hovold wrote: > >> Disabling threaded NAPI caused a severe regression in 6.5-rc5 by making >> the X13s completely unusable (e.g. no keyboard input, I've seen an RCU >> splat once). >> >> I'm supposed to be on holiday this week, but thanks to the rain I gave >> rc5 a try and ran into this. >> >> I've added Bjorn, Mani and Konrad on CC who may be able to help with >> debugging this further if needed while I'm out-of-office. > > Back from my holiday now, and this regression is still there with > 6.5-rc7. I was also away but back now. > Any chance we can get the offending commit reverted before 6.5 is > released? The problem here is that would break QCN9074 again so there is no good solution. I suspect we have a fundamental issue in ath11k which we just haven't discovered yet. I would prefer to get to the bottom of this before reverting anything. > I'll take a closer look at this meanwhile. Thanks, much appreciated. Did you try enabling all kernel debug features, maybe they would give some hints?
On Tue, Aug 22, 2023 at 03:56:24PM +0300, Kalle Valo wrote: > Johan Hovold <johan@kernel.org> writes: > > On Wed, Aug 09, 2023 at 09:34:32AM +0200, Johan Hovold wrote: > > > >> Disabling threaded NAPI caused a severe regression in 6.5-rc5 by making > >> the X13s completely unusable (e.g. no keyboard input, I've seen an RCU > >> splat once). > > Any chance we can get the offending commit reverted before 6.5 is > > released? > > The problem here is that would break QCN9074 again so there is no good > solution. I suspect we have a fundamental issue in ath11k which we just > haven't discovered yet. I would prefer to get to the bottom of this > before reverting anything. Sure, ideally we can find and fix the underlying issues these next few days, but since this regression was introduced in rc5 in an attempt to address the QCN9074 issue which has been there since 6.1 I think we need to revert otherwise. > > I'll take a closer look at this meanwhile. > > Thanks, much appreciated. Did you try enabling all kernel debug > features, maybe they would give some hints? Yes, I have a bunch of those enabled. Lockdep does not complain, but the hard lockup detector triggers and it looks like CPU0 (which handles most interrupts on this machine currently) has got stuck while processing an interrupt. RCU also detects the stall on CPU0 and provides a task dump for ksoftirqd with the following call trace: __switch_to run_ksoftirqd smpboot_thread_fn kthread ret_from_fork I just tried the out-of-tree pseudo NMI series [0] to get a stack trace, but CPU0 does not respond to those either when I hit this. Note that it takes a bit of RX to trigger this, but I hit it as soon as I try to download something substantial (e.g. after a couple of MB). Johan [0] https://lore.kernel.org/lkml/20230419225604.21204-1-dianders@chromium.org/
On Tue, Aug 22, 2023 at 03:44:45PM +0200, Johan Hovold wrote: > On Tue, Aug 22, 2023 at 03:56:24PM +0300, Kalle Valo wrote: > > Johan Hovold <johan@kernel.org> writes: > > > On Wed, Aug 09, 2023 at 09:34:32AM +0200, Johan Hovold wrote: > > > > > >> Disabling threaded NAPI caused a severe regression in 6.5-rc5 by making > > >> the X13s completely unusable (e.g. no keyboard input, I've seen an RCU > > >> splat once). > > > > Any chance we can get the offending commit reverted before 6.5 is > > > released? > > > > The problem here is that would break QCN9074 again so there is no good > > solution. I suspect we have a fundamental issue in ath11k which we just > > haven't discovered yet. I would prefer to get to the bottom of this > > before reverting anything. > > Sure, ideally we can find and fix the underlying issues these next few > days, but since this regression was introduced in rc5 in an attempt to > address the QCN9074 issue which has been there since 6.1 I think we > need to revert otherwise. I've managed to track down what causes the hang on the X13s after disabling threaded NAPI. Turns out to be a severe regression in the genirq code that causes the software resend tasklet to loop indefinitely. I've just sent a fix here: https://lore.kernel.org/lkml/20230826154004.1417-1-johan+linaro@kernel.org/ I've also made some progress on the QCN9074 hang, but keeping the threaded NAPI revert for now is indeed the right thing to do. Johan
Johan Hovold <johan@kernel.org> writes: > On Tue, Aug 22, 2023 at 03:44:45PM +0200, Johan Hovold wrote: >> On Tue, Aug 22, 2023 at 03:56:24PM +0300, Kalle Valo wrote: >> > Johan Hovold <johan@kernel.org> writes: >> > > On Wed, Aug 09, 2023 at 09:34:32AM +0200, Johan Hovold wrote: >> > > >> > >> Disabling threaded NAPI caused a severe regression in 6.5-rc5 by making >> > >> the X13s completely unusable (e.g. no keyboard input, I've seen an RCU >> > >> splat once). >> >> > > Any chance we can get the offending commit reverted before 6.5 is >> > > released? >> > >> > The problem here is that would break QCN9074 again so there is no good >> > solution. I suspect we have a fundamental issue in ath11k which we just >> > haven't discovered yet. I would prefer to get to the bottom of this >> > before reverting anything. >> >> Sure, ideally we can find and fix the underlying issues these next few >> days, but since this regression was introduced in rc5 in an attempt to >> address the QCN9074 issue which has been there since 6.1 I think we >> need to revert otherwise. > > I've managed to track down what causes the hang on the X13s after > disabling threaded NAPI. Turns out to be a severe regression in the > genirq code that causes the software resend tasklet to loop > indefinitely. > > I've just sent a fix here: > > https://lore.kernel.org/lkml/20230826154004.1417-1-johan+linaro@kernel.org/ Oh wow, that's a tricky bug :o I'm sure it was not easy to find. > I've also made some progress on the QCN9074 hang, but keeping the > threaded NAPI revert for now is indeed the right thing to do. Ok, thanks for the update and looking at also this problem. Very much appreciated! I'm sure we have a major bug lurking somewhere in ath11k, would be so good to fix that.
diff --git a/drivers/net/wireless/ath/ath11k/ahb.c b/drivers/net/wireless/ath/ath11k/ahb.c index 139da578831a..1cebba7889d7 100644 --- a/drivers/net/wireless/ath/ath11k/ahb.c +++ b/drivers/net/wireless/ath/ath11k/ahb.c @@ -376,6 +376,7 @@ static void ath11k_ahb_ext_irq_enable(struct ath11k_base *ab) struct ath11k_ext_irq_grp *irq_grp = &ab->ext_irq_grp[i]; if (!irq_grp->napi_enabled) { + dev_set_threaded(&irq_grp->napi_ndev, true); napi_enable(&irq_grp->napi); irq_grp->napi_enabled = true; } diff --git a/drivers/net/wireless/ath/ath11k/pcic.c b/drivers/net/wireless/ath/ath11k/pcic.c index c63083633b37..c899616fbee4 100644 --- a/drivers/net/wireless/ath/ath11k/pcic.c +++ b/drivers/net/wireless/ath/ath11k/pcic.c @@ -466,6 +466,7 @@ void ath11k_pcic_ext_irq_enable(struct ath11k_base *ab) struct ath11k_ext_irq_grp *irq_grp = &ab->ext_irq_grp[i]; if (!irq_grp->napi_enabled) { + dev_set_threaded(&irq_grp->napi_ndev, true); napi_enable(&irq_grp->napi); irq_grp->napi_enabled = true; }
This reverts commit d265ebe41c911314bd273c218a37088835959fa1. Disabling threaded NAPI causes the Lenovo ThinkPad X13s to hang (e.g. no more interrupts received) almost immediately during RX. Apparently something broke since commit 13aa2fb692d3 ("wifi: ath11k: Enable threaded NAPI") so that a simple revert is no longer possible. As commit d265ebe41c91 ("Revert "wifi: ath11k: Enable threaded NAPI"") does not address the underlying issue reported with QCN9074, it seems we need to reenable threaded NAPI before fixing both bugs properly. Fixes: d265ebe41c91 ("Revert "wifi: ath11k: Enable threaded NAPI"") Signed-off-by: Johan Hovold <johan+linaro@kernel.org> --- Hi Kalle, Disabling threaded NAPI caused a severe regression in 6.5-rc5 by making the X13s completely unusable (e.g. no keyboard input, I've seen an RCU splat once). I'm supposed to be on holiday this week, but thanks to the rain I gave rc5 a try and ran into this. I've added Bjorn, Mani and Konrad on CC who may be able to help with debugging this further if needed while I'm out-of-office. Johan drivers/net/wireless/ath/ath11k/ahb.c | 1 + drivers/net/wireless/ath/ath11k/pcic.c | 1 + 2 files changed, 2 insertions(+)