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Sat, 21 Dec 2024 12:31:21 +0000 (GMT) Message-ID: Date: Sat, 21 Dec 2024 18:01:20 +0530 Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] block: Revert "block: Fix potential deadlock while freezing queue and acquiring sysfs_lock" To: Ming Lei , Jens Axboe Cc: linux-block@vger.kernel.org References: <20241218101617.3275704-1-ming.lei@redhat.com> <20241218101617.3275704-2-ming.lei@redhat.com> <23c3e917-9dd3-4a0f-8bf4-0a6f421aae0e@linux.ibm.com> Content-Language: en-US From: Nilay Shroff In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: 5tbQW9p5x36DmPVScVAKskAIEBP1qAU_ X-Proofpoint-ORIG-GUID: 5tbQW9p5x36DmPVScVAKskAIEBP1qAU_ X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1051,Hydra:6.0.680,FMLib:17.12.62.30 definitions=2024-10-15_01,2024-10-11_01,2024-09-30_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 mlxscore=0 lowpriorityscore=0 clxscore=1015 mlxlogscore=999 priorityscore=1501 adultscore=0 malwarescore=0 bulkscore=0 spamscore=0 phishscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2411120000 definitions=main-2412210110 On 12/20/24 20:54, Ming Lei wrote: > On Fri, Dec 20, 2024 at 11:10 PM Jens Axboe wrote: >> >> On 12/20/24 3:23 AM, Nilay Shroff wrote: >>> On 12/18/24 15:46, Ming Lei wrote: >>>> This reverts commit be26ba96421ab0a8fa2055ccf7db7832a13c44d2. >>>> >>>> Commit be26ba96421a ("block: Fix potential deadlock while freezing queue and >>>> acquiring sysfs_loc") actually reverts commit 22465bbac53c ("blk-mq: move cpuhp >>>> callback registering out of q->sysfs_lock"), and causes the original resctrl >>>> lockdep warning. >>>> >>>> So revert it and we need to fix the issue in another way. >>>> >>> Hi Ming, >>> >>> Can we wait here for some more time before we revert this as this is >>> currently being discussed[1] and we don't know yet how we may fix it? >>> >>> [1]https://lore.kernel.org/all/20241219061514.GA19575@lst.de/ >> >> It's already queued up and will go out today. Doesn't exclude people >> working on solving this for real. > > IMO, it is correct to cut the dependency between q->sysfs_lock and > global cpu hotplug lock, otherwise more subsystems can be involved, > so let's revert it first. > Yeah agreed, we may want to in that case just remove lockdep aseert of q->sysfs_lock from blk_mq_realloc_hw_ctxs() and also remove q->sysfs_lock from blk_mq_init_allocated_queue(). But that's ok. Lets see how we'd pursue further and solve other limits-lock and queue-freeze issue. > Christoph is also working on q->sysfs_lock warning, and we can try to > figure out other solutions given the involved(or most of) locks should be > from block layer internal. > > https://lore.kernel.org/linux-block/20241219061514.GA19575@lst.de/ > Thanks, --Nilay