linux-kernel - Re: [PATCH 1/2] kref: add kref_test_and

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Date:	Tue, 04 Jan 2011 17:05:14 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Jerome Marchand <jmarchan@...hat.com>
Cc:	Vivek Goyal <vgoyal@...hat.com>, Jens Axboe <jaxboe@...ionio.com>,
	Satoru Takeuchi <takeuchi_satoru@...fujitsu.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <greg@...ah.com>
Subject: Re: [PATCH 1/2] kref: add kref_test_and_get

Le mardi 04 janvier 2011 à 16:52 +0100, Jerome Marchand a écrit :
> Add kref_test_and_get() function, which atomically add a reference only if
> refcount is not zero. This prevent to add a reference to an object that is
> already being removed.
> 
> Signed-off-by: Jerome Marchand <jmarchan@...hat.com>

> +int kref_test_and_get(struct kref *kref)
> +{
> +	int ret;
> +	smp_mb__before_atomic_inc();
> +	ret = atomic_inc_not_zero(&kref->refcount);
> +	smp_mb__after_atomic_inc();
> +	return ret;
> +}
> +
> +/**

atomic_inc_not_zero() has full memory barrier semantic already, you dont
need smp_mb__before_atomic_inc() or smp_mb__after_atomic_inc();



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