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[103.229.16.4]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-be508bfd8ffsm16315106a12.17.2025.12.02.19.38.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 02 Dec 2025 19:38:55 -0800 (PST) Message-ID: <5d71468a-e5c3-4a85-b985-466bae6af70e@oss.qualcomm.com> Date: Wed, 3 Dec 2025 11:38:52 +0800 Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] blk-mq: Abort suspend when wakeup events are pending To: Ming Lei Cc: Jens Axboe , Daniel Wagner , Hannes Reinecke , linux-arm-msm@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, pavan.kondeti@oss.qualcomm.com References: <20251202-blkmq_skip_waiting-v1-1-f73d8a977ce0@oss.qualcomm.com> From: Cong Zhang Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Proofpoint-GUID: n4qnhAENC7YDs7k58zTXm4NmkEO8aHzC X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMjAzMDAyNiBTYWx0ZWRfXxfTZqRxsO4SB uthdp/S/hEX9R/ETK6Q57HLu7Yerzt4XK8Fsp2QbZ1QhBkjFDzG2R8Bw4heWh3Xl40rDxvsy/iC a8NQhAnjlLnhINIiM1kBOKmFOG6DyY/yIZeY3GhTECGhLolSANGzo50AMW9qUmOZBiOkhG5Wi+S Zv8I7QXvpm0rwibAhXYN1Y1bhmgAl5XehxczOQVI83wJRqEBZQ9jUfIty7a3QJnvHMrJwyoSPjX oGDzcxQmrfnzdcGm4ZB7qv4nmA91QBjs/lPdijF6ZAKEvjKzDLy6UTBGO+ncicL04fDuNexfGlv 6QrrW82A0ZmyQuRELVj7Lj85aUfdHe63ZSPHd4JPNq3d1RtfTMpVUOy8VQTnLYAPADjcJ87km5w 9csB5AyBaHeT30Fm1IHN+pSrfCYd/Q== X-Proofpoint-ORIG-GUID: n4qnhAENC7YDs7k58zTXm4NmkEO8aHzC X-Authority-Analysis: v=2.4 cv=ApjjHe9P c=1 sm=1 tr=0 ts=692fb0d1 cx=c_pps a=JL+w9abYAAE89/QcEU+0QA==:117 a=nuhDOHQX5FNHPW3J6Bj6AA==:17 a=IkcTkHD0fZMA:10 a=wP3pNCr1ah4A:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=EUspDBNiAAAA:8 a=STW2nHLoXGP7JFEkyEgA:9 a=QEXdDO2ut3YA:10 a=324X-CrmTo6CU4MGRt3R:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-12-01_01,2025-11-27_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 lowpriorityscore=0 priorityscore=1501 impostorscore=0 adultscore=0 bulkscore=0 phishscore=0 spamscore=0 clxscore=1015 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2510240001 definitions=main-2512030026 On 12/2/2025 8:29 PM, Ming Lei wrote: > On Tue, Dec 02, 2025 at 05:48:21PM +0800, Cong Zhang wrote: >> >> >> On 12/2/2025 5:20 PM, Ming Lei wrote: >>> On Tue, Dec 02, 2025 at 11:56:12AM +0800, Cong Zhang wrote: >>>> During system suspend, wakeup capable IRQs for block device can be >>>> delayed, which can cause blk_mq_hctx_notify_offline() to hang >>>> indefinitely while waiting for pending request to complete. >>>> Skip the request waiting loop and abort suspend when wakeup events are >>>> pending to prevent the deadlock. >>>> >>>> Fixes: bf0beec0607d ("blk-mq: drain I/O when all CPUs in a hctx are offline") >>>> Signed-off-by: Cong Zhang >>>> --- >>>> The issue was found during system suspend with a no_soft_reset >>>> virtio-blk device. Here is the detailed analysis: >>>> - When system suspend starts and no_soft_reset is enabled, virtio-blk >>>> does not call its suspend callback. >>>> - Some requests are dispatched and queued. After sending the virtqueue >>>> notifier, the kernel waits for an IRQ to complete the request. >>>> - The virtio-blk IRQ is wakeup-capable. When the IRQ is triggered, it >>>> remains pending because the device is in the suspend process. >>> >>> Can you explain a bit for above point? Why does the IRQ remains pending >>> and not get handled? >>> >> >> The wakeup capable IRQ is not masked during suspend. When the IRQ is >> triggered, the kernel does not call its IRQ handler, instead kernel only >> marks the IRQ as a wakeup event in pm_system_irq_wakeup(). By checking >> pm_wakeup_pending() suspend process can abort if a wakeup event is >> detected. That means the actual IRQ handler is not called during the >> checking of blk_mq_hctx_has_requests, which cause the issue. > > Thanks for the explanation! > > Can you document it around `if (pm_wakeup_pending)`? > > Otherwise, this patch looks fine for me. > Thanks for your comments! Update in the new patchset. > > Thanks, > Ming >