Message-ID: <54DCB703.9020109@linux.vnet.ibm.com>
Date: Thu, 12 Feb 2015 19:51:55 +0530
From: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Organization: IBM
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To: Oleg Nesterov <oleg@redhat.com>
CC: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, peterz@infradead.org,
        torvalds@linux-foundation.org, konrad.wilk@oracle.com,
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Subject: Re: [PATCH V3] x86 spinlock: Fix memory corruption on completing
 completions
References: <1423741647-2156-1-git-send-email-raghavendra.kt@linux.vnet.ibm.com> <20150212133707.GA10232@redhat.com>
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On 02/12/2015 07:07 PM, Oleg Nesterov wrote:
> On 02/12, Raghavendra K T wrote:
>>
>> @@ -772,7 +773,8 @@ __visible void kvm_lock_spinning(struct arch_spinlock *lock, __ticket_t want)
>>   	 * check again make sure it didn't become free while
>>   	 * we weren't looking.
>>   	 */
>> -	if (ACCESS_ONCE(lock->tickets.head) == want) {
>> +	head = ACCESS_ONCE(lock->tickets.head);
>> +	if (__tickets_equal(head, want)) {
>>   		add_stats(TAKEN_SLOW_PICKUP, 1);
>
> While at it, perhaps it makes sense to s/ACCESS_ONCE/READ_ONCE/ but this
> is cosmetic.

yes.. will do.

>
> We also need to change another user of enter_slow_path, xen_lock_spinning()
> in arch/x86/xen/spinlock.c.
>

Had in mind but forgot before sending. will update resend.

> Other than that looks correct at first glance... but this is up to
> maintainers.
>

Thanks

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