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Date: Fri, 3 Aug 2018 14:36:18 +0800
From: Fam Zheng <famz@redhat.com>
Message-ID: <20180803063618.GD16395@lemon.usersys.redhat.com>
References: <20180803024217.GC16395@lemon.usersys.redhat.com>
	<2b1415a5-9553-386b-6cb5-8da000ac71da@redhat.com>
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Subject: Re: [Qemu-devel] Node deletion in aio_set_fd_handler
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-devel@nongnu.org

On Fri, 08/03 08:13, Paolo Bonzini wrote:
> On 03/08/2018 04:42, Fam Zheng wrote:
> > Paolo, is this else branch dead code (or bug?):
> > 
> >         /* If the lock is held, just mark the node as deleted */
> >         if (qemu_lockcnt_count(&ctx->list_lock)) {
> >             node->deleted = 1;
> >             node->pfd.revents = 0;
> >         } else {
> >             /* Otherwise, delete it for real.  We can't just mark it as
> >              * deleted because deleted nodes are only cleaned up while
> >              * no one is walking the handlers list.
> >              */
> >             QLIST_REMOVE(node, node);
> >             deleted = true;
> >         }
> > 
> > Since we are in a qemu_lockcnt_lock/unlock section?
> 
> No, qemu_lockcnt_count returns the number of nested qemu_lockcnt_inc/dec
> (read-side) sections.  lock/unlock is for the write side.
> 
> The comment should be improved (e.g. "if a read is in progress, just
> mark the node as deleted").

Yeah, that explains! Agree about the comment, I'll send a patch then. Thanks.

Fam