From: Paolo Bonzini <pbonzini@redhat.com>
To: Fam Zheng <famz@redhat.com>
Cc: qemu-devel@nongnu.org, mst@redhat.com
Subject: Re: [Qemu-devel] [PATCH] fixup! block-migration: acquire AioContext as necessary
Date: Tue, 23 Feb 2016 10:42:55 +0100 [thread overview]
Message-ID: <56CC299F.3040509@redhat.com> (raw)
In-Reply-To: <20160223053926.GA23182@ad.usersys.redhat.com>
On 23/02/2016 06:39, Fam Zheng wrote:
> BTW, could you also explain the blk_mig_lock() question (*) I had?
>
> *: https://lists.gnu.org/archive/html/qemu-devel/2016-02/msg03317.html
Sorry, missed that:
>
>> @@ -597,21 +627,28 @@ static void block_migration_cleanup(void *opaque)
>> {
>> BlkMigDevState *bmds;
>> BlkMigBlock *blk;
>> + AioContext *ctx;
>>
>> bdrv_drain_all();
>>
>> unset_dirty_tracking();
>>
>> - blk_mig_lock();
>
> Why is it okay to skip the blk_mig_lock() for block_mig_state.bmds_list?
The bmds_list is not protected by blk_mig_lock:
/* Written during setup phase. Can be read without a lock. */
int blk_enable;
int shared_base;
QSIMPLEQ_HEAD(bmds_list, BlkMigDevState) bmds_list;
int64_t total_sector_sum;
bool zero_blocks;
block_migration_cleanup is called from qemu_savevm_state_cleanup, when
there can be no concurrency between the migration thread and the I/O
thread. In fact the call of qemu_savevm_state_cleanup might as well be
moved out of the migration thread.
Paolo
next prev parent reply other threads:[~2016-02-23 9:43 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-19 15:10 [Qemu-devel] [PATCH] fixup! block-migration: acquire AioContext as necessary Paolo Bonzini
2016-02-23 5:39 ` Fam Zheng
2016-02-23 9:42 ` Paolo Bonzini [this message]
2016-02-23 12:56 ` Fam Zheng
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