From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: virtio-dev@lists.oasis-open.org, Joern Engel <joern@logfs.org>,
Anatol Pomozov <anatol.pomozov@gmail.com>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org, qinchuanyu@huawei.com,
davem@davemloft.net
Subject: Re: [PATCH net 1/3] kref: add kref_sub_return
Date: Wed, 12 Feb 2014 08:56:30 -0800 [thread overview]
Message-ID: <20140212165630.GA22991@kroah.com> (raw)
In-Reply-To: <1392222846-26699-2-git-send-email-mst@redhat.com>
On Wed, Feb 12, 2014 at 06:38:21PM +0200, Michael S. Tsirkin wrote:
> It is sometimes useful to get the value of the reference count after
> decrement.
> For example, vhost wants to execute some periodic cleanup operations
> once number of references drops below a specific value, before it
> reaches zero (for efficiency).
You should never care about what the value of the kref is, if you are
using it correctly :)
So I really don't want to add this function, as I'm sure people will use
it incorrectly. You should only care if the reference drops to 0, if
not, then your usage doesn't really fit into the "kref" model, and so,
just use an atomic variable.
I really want to know why it matters for "efficiency" that you know this
number. How does that help anything, as the number could then go up
later on, and the work you did at a "lower" number is obsolete, right?
thanks,
greg k-h
next prev parent reply other threads:[~2014-02-12 16:56 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-12 16:37 [PATCH net 0/3] vhost fixes for 3.14, -stable Michael S. Tsirkin
2014-02-12 16:36 ` [PATCH net 3/3] vhost: fix a theoretical race in device cleanup Michael S. Tsirkin
2014-02-12 16:38 ` [PATCH net 2/3] vhost: fix ref cnt checking deadlock Michael S. Tsirkin
2014-02-12 16:38 ` [PATCH net 1/3] kref: add kref_sub_return Michael S. Tsirkin
2014-02-12 16:56 ` Greg Kroah-Hartman [this message]
2014-02-12 17:35 ` Michael S. Tsirkin
2014-02-12 18:37 ` Greg Kroah-Hartman
2014-02-12 18:39 ` Anatol Pomozov
2014-02-13 0:06 ` David Miller
2014-02-13 1:25 ` Jörn Engel
2014-02-13 1:39 ` Greg KH
2014-02-13 4:05 ` David Miller
2014-02-13 4:09 ` David Miller
2014-02-14 0:03 ` Greg KH
2014-02-14 5:10 ` David Miller
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