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From: Paolo Bonzini <pbonzini@redhat.com>
To: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>,
	Emanuele Giuseppe Esposito <eesposit@redhat.com>,
	qemu-block@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>, John Snow <jsnow@redhat.com>,
	qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>,
	Max Reitz <mreitz@redhat.com>
Subject: Re: [PATCH v4 6/6] block-copy: atomic .cancelled and .finished fields in BlockCopyCallState
Date: Tue, 22 Jun 2021 12:20:03 +0200	[thread overview]
Message-ID: <c8b4e9b9-15a6-3ae4-cb8f-5289a221dcbe@redhat.com> (raw)
In-Reply-To: <28d4cd1c-2495-b30d-3c9f-2d8d0d3e897b@virtuozzo.com>

On 22/06/21 11:36, Vladimir Sementsov-Ogievskiy wrote:
>> It does.  If it returns true, you still want the load of finished to 
>> happen before the reads that follow.
> 
> Hmm.. The worst case if we use just qatomic_read is that assertion will 
> not crash when it actually should. That doesn't break the logic. But 
> that's not good anyway.
> 
> OK, I agree, let's keep it.

You can also have a finished job, but get a stale value for 
error_is_read or ret.  The issue is not in getting the stale value per 
se, but in block_copy_call_status's caller not expecting it.

(I understand you agree, but I guess it can be interesting to learn 
about this too).

Paolo



  reply	other threads:[~2021-06-22 10:34 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-14  7:33 [PATCH v4 0/6] block-copy: protect block-copy internal structures Emanuele Giuseppe Esposito
2021-06-14  7:33 ` [PATCH v4 1/6] block-copy: small refactor in block_copy_task_entry and block_copy_common Emanuele Giuseppe Esposito
2021-06-19 14:33   ` Vladimir Sementsov-Ogievskiy
2021-06-14  7:33 ` [PATCH v4 2/6] block-copy: streamline choice of copy_range vs. read/write Emanuele Giuseppe Esposito
2021-06-19 15:05   ` Vladimir Sementsov-Ogievskiy
2021-06-19 18:23   ` Vladimir Sementsov-Ogievskiy
2021-06-14  7:33 ` [PATCH v4 3/6] block-copy: improve comments of BlockCopyTask and BlockCopyState types and functions Emanuele Giuseppe Esposito
2021-06-19 15:23   ` Vladimir Sementsov-Ogievskiy
2021-06-19 18:31     ` Vladimir Sementsov-Ogievskiy
2021-06-21  8:13       ` Emanuele Giuseppe Esposito
2021-06-22  9:20         ` Vladimir Sementsov-Ogievskiy
2021-06-21  7:59     ` Emanuele Giuseppe Esposito
2021-06-22  9:16       ` Vladimir Sementsov-Ogievskiy
2021-06-19 17:27   ` Vladimir Sementsov-Ogievskiy
2021-06-21  8:21     ` Emanuele Giuseppe Esposito
2021-06-19 18:53   ` Vladimir Sementsov-Ogievskiy
2021-06-21  8:28     ` Emanuele Giuseppe Esposito
2021-06-14  7:33 ` [PATCH v4 4/6] block-copy: move progress_set_remaining in block_copy_task_end Emanuele Giuseppe Esposito
2021-06-14  7:33 ` [PATCH v4 5/6] block-copy: add a CoMutex Emanuele Giuseppe Esposito
2021-06-19 19:34   ` Vladimir Sementsov-Ogievskiy
2021-06-14  7:33 ` [PATCH v4 6/6] block-copy: atomic .cancelled and .finished fields in BlockCopyCallState Emanuele Giuseppe Esposito
2021-06-19 20:06   ` Vladimir Sementsov-Ogievskiy
2021-06-21  9:30     ` Emanuele Giuseppe Esposito
2021-06-22  9:56       ` Vladimir Sementsov-Ogievskiy
2021-06-22  8:15     ` Paolo Bonzini
2021-06-22  9:36       ` Vladimir Sementsov-Ogievskiy
2021-06-22 10:20         ` Paolo Bonzini [this message]
2021-06-22 10:39           ` Vladimir Sementsov-Ogievskiy
2021-06-22 20:57             ` Emanuele Giuseppe Esposito
2021-06-23 10:06             ` Paolo Bonzini

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