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

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Message-ID: <20170127220958.GA2476@mtj.duckdns.org>
Date:   Fri, 27 Jan 2017 17:09:58 -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,
        Guilherme Piccoli <gpiccoli@...ibm.com>
Subject: Re: [PATCH 1/1] percpu-refcount: fix reference leak during
 percpu-atomic transition

Hello, Douglas.

On Fri, Jan 27, 2017 at 02:59:08PM -0600, Douglas Miller wrote:
> @@ -212,7 +212,7 @@ static inline bool percpu_ref_tryget(struct percpu_ref *ref)
>  		this_cpu_inc(*percpu_count);
>  		ret = true;
>  	} else {
> -		ret = atomic_long_inc_not_zero(&ref->count);
> +		ret = (atomic_long_inc_not_zero(&ref->count) != 0);
>  	}
>  
>  	rcu_read_unlock_sched();
> @@ -246,7 +246,7 @@ static inline bool percpu_ref_tryget_live(struct percpu_ref *ref)
>  		this_cpu_inc(*percpu_count);
>  		ret = true;
>  	} else if (!(ref->percpu_count_ptr & __PERCPU_REF_DEAD)) {
> -		ret = atomic_long_inc_not_zero(&ref->count);
> +		ret = (atomic_long_inc_not_zero(&ref->count) != 0);

Ugh.... Damn it.  This is why we use bools instead of ints for these
things.  For some reason, we're returning bools but using an integer
variable to cache the result.  :(

Can you please convert the local variable to bool instead?

Thanks a lot for spotting this.

-- 
tejun