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From: Bart Van Assche <bvanassche@acm.org>
To: Ming Lei <ming.lei@redhat.com>
Cc: "Martin K . Petersen" <martin.petersen@oracle.com>,
	linux-scsi@vger.kernel.org
Subject: Re: [PATCH 0/4] Revert "Call blk_mq_free_tag_set() earlier"
Date: Mon, 29 Aug 2022 05:14:09 -0700	[thread overview]
Message-ID: <a4dedbb9-8a7f-2576-11a5-322aedd6e9fe@acm.org> (raw)
In-Reply-To: <CAFj5m9Ka4-Ee9E7Wo4R7+FrscYZ+GU4EThoweFNRMOR6rPMxJA@mail.gmail.com>

On 8/29/22 02:14, Ming Lei wrote:
> On Mon, Aug 22, 2022 at 6:05 AM Bart Van Assche <bvanassche@acm.org> wrote:
>> Since a device, target or host reference may be held when scsi_remove_host()
>> or scsi_remove_target() is called and since te patch series "Call
>> blk_mq_free_tag_set() earlier" makes these functions wait until all references
>> are gone, that patch series may trigger a deadlock. Hence this request to
>> revert the patch series "Call blk_mq_free_tag_set() earlier".
> 
> Care to share the deadlock details? Such as dmesg log or theory behind.

Hi Ming,

Details of two different deadlock scenarios are available here:
* [syzbot] INFO: task hung in scsi_remove_host 
(https://lore.kernel.org/all/000000000000b5187d05e6c08086@google.com/).
* https://lore.kernel.org/all/Yv%2FMKymRC9O04Nqu@google.com/. The link 
[2] in this email includes a call trace and instructions for reproducing 
this issue. My root cause analysis of this deadlock is available here: 
https://lore.kernel.org/all/27d0dde8-344c-1dd0-cc26-0e10c4e1f296@acm.org/.

Thanks,

Bart.

  reply	other threads:[~2022-08-29 12:31 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-08-21 22:04 [PATCH 0/4] Revert "Call blk_mq_free_tag_set() earlier" Bart Van Assche
2022-08-21 22:04 ` [PATCH 1/4] scsi: core: " Bart Van Assche
2022-08-21 22:05 ` [PATCH 2/4] scsi: core: Revert "Simplify LLD module reference counting" Bart Van Assche
2022-08-21 22:05 ` [PATCH 3/4] scsi: core: Revert "Make sure that hosts outlive targets" Bart Van Assche
2022-08-21 22:05 ` [PATCH 4/4] scsi: core: Revert "Make sure that targets outlive devices" Bart Van Assche
2022-08-29  9:14 ` [PATCH 0/4] Revert "Call blk_mq_free_tag_set() earlier" Ming Lei
2022-08-29 12:14   ` Bart Van Assche [this message]
2022-09-01  5:12 ` Martin K. Petersen

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