From: Paolo Bonzini <pbonzini@redhat.com>
To: Fam Zheng <famz@redhat.com>
Cc: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH v2 4/4] dma-helpers: Move reschedule_dma BH to blk's AioContext
Date: Fri, 13 Mar 2015 11:48:20 +0100 [thread overview]
Message-ID: <5502C074.2060807@redhat.com> (raw)
In-Reply-To: <20150313085847.GC3527@ad.nay.redhat.com>
On 13/03/2015 09:58, Fam Zheng wrote:
>> >
>> > This looks good. However, I wonder if dma_aio_cancel should also call
>> > cpu_unregister_map_client. In this case, it's much better to just use a
>> > lock for the list (though you can still use atomics for the in-use flag).
> The other possibility is grab a reference for the cpu_register_map_client call,
> and release it in reschedule_dma. This way the atomics can keep, but we'll need
> a "finished" flag in DMAAIOCB to avoid double completion.
Considering this is a slow path, a lock seems preferrable.
It's not that your patch were bad, it's that a pre-existing bug got in
your way, and broke the assumptions you made.
Paolo
next prev parent reply other threads:[~2015-03-13 10:48 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-13 1:38 [Qemu-devel] [PATCH v2 0/4] exec: Make bounce buffer thread safe Fam Zheng
2015-03-13 1:38 ` [Qemu-devel] [PATCH v2 1/4] exec: Atomic access to bounce buffer Fam Zheng
2015-03-13 8:09 ` Paolo Bonzini
2015-03-13 8:16 ` Fam Zheng
2015-03-13 8:32 ` Paolo Bonzini
2015-03-13 8:38 ` Fam Zheng
2015-03-13 8:41 ` Paolo Bonzini
2015-03-13 1:38 ` [Qemu-devel] [PATCH v2 2/4] exec: Atomic access to map_client_list Fam Zheng
2015-03-13 8:11 ` Paolo Bonzini
2015-03-13 1:38 ` [Qemu-devel] [PATCH v2 3/4] exec: Notify cpu_register_map_client caller if the bounce buffer is available Fam Zheng
2015-03-13 8:12 ` Paolo Bonzini
2015-03-13 1:38 ` [Qemu-devel] [PATCH v2 4/4] dma-helpers: Move reschedule_dma BH to blk's AioContext Fam Zheng
2015-03-13 8:13 ` Paolo Bonzini
2015-03-13 8:58 ` Fam Zheng
2015-03-13 10:48 ` Paolo Bonzini [this message]
2015-03-13 12:33 ` Paolo Bonzini
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