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Subject: Re: [PATCH] wifi: ath12k: fix race due to setting
 ATH12K_FLAG_EXT_IRQ_ENABLED too early
From: Kalle Valo <kvalo@kernel.org>
In-Reply-To: <20240524023642.37030-1-quic_bqiang@quicinc.com>
References: <20240524023642.37030-1-quic_bqiang@quicinc.com>
To: Baochen Qiang <quic_bqiang@quicinc.com>
Cc: <ath12k@lists.infradead.org>, <linux-wireless@vger.kernel.org>,
 <quic_bqiang@quicinc.com>
User-Agent: pwcli/0.1.1-git (https://github.com/kvalo/pwcli/) Python/3.11.2
Message-ID: <171691830369.1700985.14695281653028868170.kvalo@kernel.org>
Date: Tue, 28 May 2024 17:45:05 +0000 (UTC)

Baochen Qiang <quic_bqiang@quicinc.com> wrote:

> Commit 5082b3e3027e ("wifi: ath11k: fix race due to setting
> ATH11K_FLAG_EXT_IRQ_ENABLED too early") fixes a race in ath11k
> driver. Since ath12k shares the same logic as ath11k, currently
> the race also exists in ath12k: in ath12k_pci_ext_irq_enable(),
> ATH12K_FLAG_EXT_IRQ_ENABLED is set before NAPI is enabled.
> In cases where only one MSI vector is allocated, this results
> in a race condition: after ATH12K_FLAG_EXT_IRQ_ENABLED is set
> but before NAPI enabled, CE interrupt breaks in. Since IRQ is
> shared by CE and data path, ath12k_pci_ext_interrupt_handler()
> is also called where we call disable_irq_nosync() to disable
> IRQ. Then napi_schedule() is called but it does nothing because
> NAPI is not enabled at that time, meaning that
> ath12k_pci_ext_grp_napi_poll() will never run, so we have
> no chance to call enable_irq() to enable IRQ back. Since IRQ
> is shared, all interrupts are disabled and we would finally
> get no response from target.
> 
> So port ath11k fix here, this is done by setting
> ATH12K_FLAG_EXT_IRQ_ENABLED after all NAPI and IRQ work are
> done. With the fix, we are sure that by the time
> ATH12K_FLAG_EXT_IRQ_ENABLED is set, NAPI is enabled.
> 
> Note that the fix above also introduce some side effects:
> if ath12k_pci_ext_interrupt_handler() breaks in after NAPI
> enabled but before ATH12K_FLAG_EXT_IRQ_ENABLED set, nothing
> will be done by the handler this time, the work will be
> postponed till the next time the IRQ fires.
> 
> This is found during code review.
> 
> Tested-on: WCN7850 hw2.0 PCI WLAN.HMT.1.0.c5-00481-QCAHMTSWPL_V1.0_V2.0_SILICONZ-3
> 
> Signed-off-by: Baochen Qiang <quic_bqiang@quicinc.com>
> Acked-by: Jeff Johnson <quic_jjohnson@quicinc.com>
> Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>

Patch applied to ath-next branch of ath.git, thanks.

0a993772e0f0 wifi: ath12k: fix race due to setting ATH12K_FLAG_EXT_IRQ_ENABLED too early

-- 
https://patchwork.kernel.org/project/linux-wireless/patch/20240524023642.37030-1-quic_bqiang@quicinc.com/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches