lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <53A243B8.4010501@cn.fujitsu.com>
Date:	Thu, 19 Jun 2014 09:58:16 +0800
From:	Lai Jiangshan <laijs@...fujitsu.com>
To:	Tejun Heo <tj@...nel.org>
CC:	<cl@...ux-foundation.org>, <kmo@...erainc.com>,
	<linux-kernel@...r.kernel.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH 6/6] percpu-refcount: implement percpu_ref_reinit() and
 percpu_ref_is_zero()

On 06/18/2014 11:32 PM, Tejun Heo wrote:
> On Wed, Jun 18, 2014 at 11:37:35AM +0800, Lai Jiangshan wrote:
>>> @@ -97,7 +98,10 @@ static inline void percpu_ref_kill(struct percpu_ref *ref)
>>>  static inline bool __pcpu_ref_alive(struct percpu_ref *ref,
>>>  				    unsigned __percpu **pcpu_countp)
>>>  {
>>> -	unsigned long pcpu_ptr = ACCESS_ONCE(ref->pcpu_count_ptr);
>>> +	unsigned long pcpu_ptr;
>>> +
>>> +	/* paired with smp_store_release() in percpu_ref_reinit() */
>>> +	pcpu_ptr = smp_load_acquire(&ref->pcpu_count_ptr);
>>
>>
>> Does "smp_load_acquire()" hurts the performance of percpu_ref_get/put()
>> in non-x86 system?
> 
> It's equivalent to data dependency barrier.  The only arch which needs
> something more than barrier() is alpha.  It isn't an issue.
> 

But I searched from the source, smp_load_acquire() is just barrier() in
x86, arm64, ia64, s390, sparc, but it includes memory barrier 
instruction in other archs.

CC Paul. If smp_load_acquire() is sufficient lightweight, I would update
the SRCU.

Thanks,
Lai
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ