From: Paolo Bonzini <pbonzini@redhat.com>
To: Peter Xu <peterx@redhat.com>
Cc: drjones@redhat.com, lersek@redhat.com, armbru@redhat.com,
qemu-devel@nongnu.org, famz@redhat.com, lcapitulino@redhat.com
Subject: Re: [Qemu-devel] [PATCH v3 10/12] Dump: add qmp command "query-dump"
Date: Tue, 1 Dec 2015 10:54:48 +0100 [thread overview]
Message-ID: <565D6E68.1060303@redhat.com> (raw)
In-Reply-To: <20151201035755.GI21032@pxdev.xzpeter.org>
On 01/12/2015 04:57, Peter Xu wrote:
>> > You need a mutex around the reads of ->status and ->written_size.
> Could I avoid using mutex here? Let me try to explain what I
> thought.
>
> The concurrency of this should only happen when:
>
> - detached dump thread is working (dump thread)
> - user queries dump status (main thread)
>
> What the dump thread is doing should be something like:
>
> - [start dumping]
> - inc written_size
> - inc written_size
> - ...
> - inc written_size
> - set ->status to COMPLETED|FAILED
> - [end dumping]
Yes, it's possible but you need to use atomic_mb_read/atomic_mb_set to
write ->status. Otherwise a CPU can see the write to ->status before
some of the final writes to ->written_size.
Paolo
next prev parent reply other threads:[~2015-12-01 9:55 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-30 11:32 [Qemu-devel] [PATCH v3 00/12] Add basic "detach" support for dump-guest-memory Peter Xu
2015-11-30 11:32 ` [Qemu-devel] [PATCH v3 01/12] dump-guest-memory: cleanup: removing dump_{error|cleanup}() Peter Xu
2015-11-30 11:32 ` [Qemu-devel] [PATCH v3 02/12] dump-guest-memory: add "detach" flag for QMP/HMP interfaces Peter Xu
2015-11-30 22:05 ` Eric Blake
2015-12-01 2:18 ` Peter Xu
2015-12-01 15:09 ` Paolo Bonzini
2015-12-02 2:31 ` Peter Xu
2015-11-30 11:32 ` [Qemu-devel] [PATCH v3 03/12] dump-guest-memory: using static DumpState, add DumpStatus Peter Xu
2015-11-30 13:00 ` Paolo Bonzini
2015-12-01 2:57 ` Peter Xu
2015-11-30 22:08 ` Eric Blake
2015-12-01 3:04 ` Peter Xu
2015-11-30 11:32 ` [Qemu-devel] [PATCH v3 04/12] dump-guest-memory: add dump_in_progress() helper function Peter Xu
2015-11-30 11:32 ` [Qemu-devel] [PATCH v3 05/12] dump-guest-memory: introduce dump_process() " Peter Xu
2015-11-30 12:55 ` Paolo Bonzini
2015-12-01 3:12 ` Peter Xu
2015-11-30 11:32 ` [Qemu-devel] [PATCH v3 06/12] dump-guest-memory: disable dump when in INMIGRATE state Peter Xu
2015-11-30 11:32 ` [Qemu-devel] [PATCH v3 07/12] dump-guest-memory: add "detach" support Peter Xu
2015-11-30 11:32 ` [Qemu-devel] [PATCH v3 08/12] dump-guest-memory: add qmp event DUMP_COMPLETED Peter Xu
2015-11-30 22:12 ` Eric Blake
2015-12-01 3:27 ` Peter Xu
2015-11-30 11:32 ` [Qemu-devel] [PATCH v3 09/12] DumpState: adding total_size and written_size fields Peter Xu
2015-11-30 11:32 ` [Qemu-devel] [PATCH v3 10/12] Dump: add qmp command "query-dump" Peter Xu
2015-11-30 12:56 ` Paolo Bonzini
2015-12-01 3:57 ` Peter Xu
2015-12-01 9:54 ` Paolo Bonzini [this message]
2015-12-01 12:32 ` Peter Xu
2015-12-01 12:37 ` Paolo Bonzini
2015-12-01 12:45 ` Peter Xu
2015-12-01 12:47 ` Paolo Bonzini
2015-12-01 13:03 ` Peter Xu
2015-11-30 22:17 ` Eric Blake
2015-12-01 4:40 ` Peter Xu
2015-12-01 13:43 ` Eric Blake
2015-11-30 11:32 ` [Qemu-devel] [PATCH v3 11/12] Dump: add hmp command "info dump" Peter Xu
2015-11-30 11:32 ` [Qemu-devel] [PATCH v3 12/12] Dump: enhance the documentations Peter Xu
2015-11-30 22:22 ` Eric Blake
2015-12-01 4:21 ` Peter Xu
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