linux-kernel - Re: [PATCH V3 1/1] percpu-refcount: fix reference leak during percpu-atomic transition

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Message-ID: <20170128125251.GA5797@mtj.duckdns.org>
Date:   Sat, 28 Jan 2017 07:52:51 -0500
From:   Tejun Heo <tj@...nel.org>
To:     Douglas Miller <dougmill@...ux.vnet.ibm.com>
Cc:     linux-kernel@...r.kernel.org, Christoph Lameter <cl@...ux.com>,
        linux-block@...r.kernel.org, stable@...r.kernel.org,
        Guilherme Piccoli <gpiccoli@...ibm.com>
Subject: Re: [PATCH V3 1/1] percpu-refcount: fix reference leak during
 percpu-atomic transition

On Sat, Jan 28, 2017 at 06:42:20AM -0600, Douglas Miller wrote:
> percpu_ref_tryget() and percpu_ref_tryget_live() should return
> "true" IFF they acquire a reference. But the return value from
> atomic_long_inc_not_zero() is a long and may have high bits set,
> e.g. PERCPU_COUNT_BIAS, and the return value of the tryget routines
> is bool so the reference may actually be acquired but the routines
> return "false" which results in a reference leak since the caller
> assumes it does not need to do a corresponding percpu_ref_put().

Applied to percpu/for-4.10-fixes w/ stable cc'd.

Thanks!

-- 
tejun