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Date: Mon, 3 Apr 2017 17:24:43 +0200
From: Alberto Garcia <berto@igalia.com>
Message-ID: <20170403152443.GA20459@igalia.com>
References: <13fddf65-e573-cf01-593d-6b02a3071721@redhat.com>
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Subject: Re: [Qemu-devel] help debugging throttle crash
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To: Eric Blake <eblake@redhat.com>
Cc: "Qemu-devel@nongnu.org" <Qemu-devel@nongnu.org>, qemu block <qemu-block@nongnu.org>, Kevin Wolf <kwolf@redhat.com>

On Mon, Apr 03, 2017 at 09:07:02AM -0500, Eric Blake wrote:

> At this point, it looks like no one is calling
> throttle_group_unregister_blk() as a result of the 'device_del',
> which leaves stale memory around

I see, I can also reproduce this very easily.

I wonder if it's not enough to simply disable I/O limits when a
BlockBackend is deleted?

--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -230,6 +230,9 @@ static void blk_delete(BlockBackend *blk)
     assert(!blk->refcnt);
     assert(!blk->name);
     assert(!blk->dev);
+    if (blk->public.throttle_state) {
+        blk_io_limits_disable(blk);
+    }
     if (blk->root) {
         blk_remove_bs(blk);
     }

Berto