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From: Paolo Bonzini <pbonzini@redhat.com>
To: Fiona Ebner <f.ebner@proxmox.com>,
	QEMU Developers <qemu-devel@nongnu.org>
Cc: Kevin Wolf <kwolf@redhat.com>, Hanna Reitz <hreitz@redhat.com>,
	John Snow <jsnow@redhat.com>,
	Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>,
	"open list:Network Block Dev..." <qemu-block@nongnu.org>,
	Thomas Lamprecht <t.lamprecht@proxmox.com>
Subject: Re: deadlock when using iothread during backup_clean()
Date: Tue, 5 Sep 2023 13:42:32 +0200	[thread overview]
Message-ID: <dd12f39d-a364-b186-2ad7-04343ea85e3f@redhat.com> (raw)
In-Reply-To: <bcbd48da-e4cc-f9c9-000c-6a9f98ca156f@proxmox.com>

On 9/5/23 12:01, Fiona Ebner wrote:
> Can we assume block_job_remove_all_bdrv() to always hold the job's
> AioContext?

I think so, see job_unref_locked(), job_prepare_locked() and 
job_finalize_single_locked().  These call the callbacks that ultimately 
get to block_job_remove_all_bdrv().
	
> And if yes, can we just tell bdrv_graph_wrlock() that it
> needs to release that before polling to fix the deadlock?

No, but I think it should be released and re-acquired in 
block_job_remove_all_bdrv() itself.

mirror_exit_common() however holds _two_ AioContext locks at the time it 
calls block_job_remove_all_bdrv(), qemu_get_aio_context() has to be 
released and reacquired in mirror_exit_common() itself.

Paolo



  parent reply	other threads:[~2023-09-05 11:43 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-09-05 10:01 deadlock when using iothread during backup_clean() Fiona Ebner
2023-09-05 11:25 ` Fiona Ebner
2023-10-04 16:51   ` Vladimir Sementsov-Ogievskiy
2023-09-05 11:42 ` Paolo Bonzini [this message]
2023-09-28  8:06   ` Fiona Ebner
2023-10-04 17:08     ` Vladimir Sementsov-Ogievskiy
2023-10-06 12:18       ` Fiona Ebner
2023-10-17 10:18         ` Fiona Ebner
2023-10-17 12:12           ` Kevin Wolf
2023-10-17 13:37             ` Fiona Ebner
2023-10-17 14:20               ` Kevin Wolf
2023-10-18  9:42                 ` Fiona Ebner
2023-10-19 12:14                   ` Kevin Wolf
2023-10-19 13:53                     ` Fiona Ebner
2023-10-20 13:52                       ` Fiona Ebner
2023-11-03 13:20                         ` Fiona Ebner

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