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[103.229.16.4]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-29bce416f00sm148351595ad.4.2025.12.02.01.48.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 02 Dec 2025 01:48:24 -0800 (PST) Message-ID: Date: Tue, 2 Dec 2025 17:48:21 +0800 Precedence: bulk X-Mailing-List: linux-kernel@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: SNuPS5qnGXU8A-X3DXzhrhaFSo8KyN8p X-Authority-Analysis: v=2.4 cv=GMsF0+NK c=1 sm=1 tr=0 ts=692eb5ea 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=GTZyfoVqD6E8GamsXEIA:9 a=QEXdDO2ut3YA:10 a=324X-CrmTo6CU4MGRt3R:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMjAyMDA3OCBTYWx0ZWRfX6nn34I6QYMdp M4Wc0b27uIoB0/CpQdGvxoqTLi2lGj9Gb/sZCJWCdYQFUj7oPuK6YkgmdpeQa3nl557bFMAmp9X fDVumyqi+wZ2GjGRzLBJwhDqtC1P2/KyE1HJO0vDmc0Lq1m7LtfvM9aIci2AQhxDE7iFp6jAB8y JFzRQyoWFF2b2aOKL0gfodFtP/fc9+HUV7lOJAZd6Ds/qPOdTixRkO9Z1m9l3rt8iNtMXGUoQQy Y9/9gyRZmbVDECoJpqDZN9ogYlHcC1AAgLq0kn5AIl9DyrhumVMVxorJ/lCz8sRz/NDxMEQCDOJ NVr+bFcS+4v9wpql+Sv1J3Az+f7r+5luI27q1CUBSnHxPBUhuh8Plb4T0JR1W2ElICa6RxaPvty hqv9cHH0PSGxZ54Mo+WSnmp/bKKNnA== X-Proofpoint-ORIG-GUID: SNuPS5qnGXU8A-X3DXzhrhaFSo8KyN8p 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 priorityscore=1501 lowpriorityscore=0 bulkscore=0 malwarescore=0 impostorscore=0 suspectscore=0 clxscore=1015 adultscore=0 phishscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2510240001 definitions=main-2512020078 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, > Ming >