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From: Julien Grall <julien.grall@arm.com>
To: Boris Ostrovsky <boris.ostrovsky@oracle.com>, xen-devel@lists.xen.org
Cc: sstabellini@kernel.org, wei.liu2@citrix.com,
	George.Dunlap@eu.citrix.com, andrew.cooper3@citrix.com,
	ian.jackson@eu.citrix.com, tim@xen.org, jbeulich@suse.com
Subject: Re: [PATCH v7 6/9] spinlock: Introduce spin_lock_cb()
Date: Mon, 14 Aug 2017 15:42:32 +0100	[thread overview]
Message-ID: <85a9edf7-7d6d-3257-874c-8b18b38b9158@arm.com> (raw)
In-Reply-To: <77fcdcda-b0fa-cdda-2fee-24eace93c011@oracle.com>



On 14/08/17 15:39, Boris Ostrovsky wrote:
>
>>>
>>> +#define spin_lock_kick(l)                       \
>>> +({                                              \to understand why
>>> you need a stronger one here
>>> +    smp_mb();                                   \
>>
>> arch_lock_signal() has already a barrier for ARM. So we have a double
>> barrier now.
>>
>> However, the barrier is slightly weaker (smp_wmb()). I am not sure why
>> you need to use a stronger barrier here. What you care is the write to
>> be done before signaling, read does not much matter. Did I miss anything?
>
> Yes, smp_wmb() should be sufficient.
>
> Should I then add arch_lock_signal_wmb() --- defined as
> arch_lock_signal() for ARM and smp_wmb() for x86?

I am not an x86 expert. Do you know why the barrier is not in 
arch_lock_signal() today?

>
>
> -boris
>
>>
>> Cheers,
>>
>>> +    arch_lock_signal();                         \
>>> +})
>>> +
>>>  /* Ensure a lock is quiescent between two critical operations. */
>>>  #define spin_barrier(l)               _spin_barrier(l)
>>>
>>>
>>
>

-- 
Julien Grall

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  reply	other threads:[~2017-08-14 14:42 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-08 21:44 [PATCH v7 0/9] Memory scrubbing from idle loop Boris Ostrovsky
2017-08-08 21:44 ` [PATCH v7 1/9] mm: Clean up free_heap_pages() Boris Ostrovsky
2017-08-10 12:21   ` Wei Liu
2017-08-14 10:30   ` Jan Beulich
2017-08-08 21:45 ` [PATCH v7 2/9] mm: Place unscrubbed pages at the end of pagelist Boris Ostrovsky
2017-08-14 10:37   ` Jan Beulich
2017-08-14 14:29     ` Boris Ostrovsky
2017-08-15  8:18       ` Jan Beulich
2017-08-15 14:41         ` Boris Ostrovsky
2017-08-15 14:51           ` Jan Beulich
2017-08-15 14:52             ` Julien Grall
2017-08-15 15:03               ` Boris Ostrovsky
2017-08-15 15:08                 ` Jan Beulich
2017-08-14 11:16   ` Julien Grall
2017-08-08 21:45 ` [PATCH v7 3/9] mm: Extract allocation loop from alloc_heap_pages() Boris Ostrovsky
2017-08-08 21:45 ` [PATCH v7 4/9] mm: Scrub pages in alloc_heap_pages() if needed Boris Ostrovsky
2017-08-08 21:45 ` [PATCH v7 5/9] mm: Scrub memory from idle loop Boris Ostrovsky
2017-08-08 21:45 ` [PATCH v7 6/9] spinlock: Introduce spin_lock_cb() Boris Ostrovsky
2017-08-14 11:22   ` Julien Grall
2017-08-14 14:39     ` Boris Ostrovsky
2017-08-14 14:42       ` Julien Grall [this message]
2017-08-14 14:57         ` Boris Ostrovsky
2017-08-08 21:45 ` [PATCH v7 7/9] mm: Keep heap accessible to others while scrubbing Boris Ostrovsky
2017-08-14 10:38   ` Jan Beulich
2017-08-08 21:45 ` [PATCH v7 8/9] mm: Print number of unscrubbed pages in 'H' debug handler Boris Ostrovsky
2017-08-08 21:45 ` [PATCH v7 9/9] mm: Make sure pages are scrubbed Boris Ostrovsky

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