Received-SPF: pass (google.com: domain of linux-wireless-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <1598243612-4627-1-git-send-email-wgong@codeaurora.org>
 <CABPxzYLjys+cXXRM5J680ZOs+6VrYt=_3rWv-gqkCod=-A1VrA@mail.gmail.com>
 <fd98989a87f2a50655dc95bdcd535c0d@codeaurora.org> <CABPxzYKvPwtQwxMfRcv9jT+d92ErhYGR91SKBH86T3Rd2QH9Qg@mail.gmail.com>
 <2d6362ce85956d0f7df2e596b89a7028@codeaurora.org> <CABPxzY+Fc22ke1ygRnDs0Uds0a7n=792QN8ALXciDrnx9SQuqQ@mail.gmail.com>
 <663fbb682fd8df555b2964d7d86b8eca@codeaurora.org>
In-Reply-To: <663fbb682fd8df555b2964d7d86b8eca@codeaurora.org>
From:   Krishna Chaitanya <chaitanya.mgit@gmail.com>
Date:   Tue, 25 Aug 2020 13:54:49 +0530
Message-ID: <CABPxzYJ982LdcUD3a_tyu3rrqp+iacZrmAp4zG_3HqCiDCR_2w@mail.gmail.com>
Subject: Re: [PATCH v2] ath10k: add flag to protect napi operation to avoid
 dead loop hang for SDIO
To:     Wen Gong <wgong@codeaurora.org>
Cc:     ath10k <ath10k@lists.infradead.org>,
        linux-wireless <linux-wireless@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-wireless-owner@vger.kernel.org
Precedence: bulk

On Tue, Aug 25, 2020 at 9:11 AM Wen Gong <wgong@codeaurora.org> wrote:
>
> On 2020-08-24 19:15, Krishna Chaitanya wrote:
> > On Mon, Aug 24, 2020 at 4:15 PM Wen Gong <wgong@codeaurora.org> wrote:
> >>
> >> On 2020-08-24 18:03, Krishna Chaitanya wrote:
> >> > On Mon, Aug 24, 2020 at 3:10 PM Wen Gong <wgong@codeaurora.org> wrote:
> >> >>
> >> >> On 2020-08-24 16:35, Krishna Chaitanya wrote:
> >> >> > On Mon, Aug 24, 2020 at 10:03 AM Wen Gong <wgong@codeaurora.org> wrote:
> >> >> >>
> >> >> >> It happened "Kernel panic - not syncing: hung_task: blocked tasks"
> >> >> >> when
> >> >> >> test simulate crash and ifconfig down/rmmod meanwhile.
> >> >> >>
> >> >> ...
> >> >> >>
> >> >> >>  #ifdef CONFIG_PM
> >> >> > Even though your DUT is SDIO based we should be doing this in general
> >> >> > for all, no?
> >> >> > core_restart + hif_stop is common to all.
> >> >> this patch does not have core_restart.
> >> > I was referring to the combination which is causing the issue.
> >> >
> >> >> I dit not hit the issue for others bus(PCIe,SNOC...), so I can not
> >> >> change them with a
> >> >> assumption they also have this issue.
> >> > But that doesn't make sense, the combination is being hit for others
> >> > also.
> >> > (they should also endup calling napi_disable twice?) or they are using
> >> > some other check to avoid this (doesn't appear so from a quick look at
> >> > the
> >> > code).
> >> Because I only use SDIO, I did not use others BUS, so I did not hit
> >> the
> >> issue
> >> on other BUS.
> > I understand, my point was based on the description the issue looks
> > independent
> > of the BUS type, so, the fix should also be generic. I understand that
> > your testing
> > is only focused on SDIO, but we should have a generic fix and probably
> > use
> > communities help to get it tested rather than fixing SDIO only.
> I checked the ath10k, only sdio.c, snoc.c, pci.c have used napi.
> I think it can change to move the
> napi_synchronize/napi_disable/napi_enable from
> sido.c/snoc.c/pci.c to ath10k_core.ko as below:
> void ath10k_core_napi_enable(struct ath10k *ar)
> {
>         if (!ar->napi_enabled) {
>                 napi_enable(&ar->napi);
>                 ar->napi_enabled = true;
>         }
> }
> EXPORT_SYMBOL(ath10k_core_napi_enable);
>
> void ath10k_core_napi_disable_sync(struct ath10k *ar)
> {
>         if (ar->napi_enabled) {
>                 napi_synchronize(&ar->napi);
>                 napi_disable(&ar->napi);
>                 ar->napi_enabled = false;
>         }
> }
> EXPORT_SYMBOL(ath10k_core_napi_disable_sync);
>
> is it appropriate?
> ...
Yes, this is perfect. One minor comment you can just do the
check initially and return.

if (ar->napi_enabled)
   return