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From: zhoucm1 <david1.zhou@amd.com>
To: "Nicolai Hähnle" <nhaehnle@gmail.com>, linux-kernel@vger.kernel.org
Cc: "Peter Zijlstra" <peterz@infradead.org>,
	"Maarten Lankhorst" <dev@mblankhorst.nl>,
	"Ingo Molnar" <mingo@redhat.com>,
	dri-devel@lists.freedesktop.org,
	"Nicolai Hähnle" <Nicolai.Haehnle@amd.com>
Subject: Re: [PATCH v3 03/12] locking/ww_mutex: Extract stamp comparison to __ww_mutex_stamp_after
Date: Thu, 22 Dec 2016 09:58:30 +0800	[thread overview]
Message-ID: <585B3346.2020001@amd.com> (raw)
In-Reply-To: <1482346000-9927-4-git-send-email-nhaehnle@gmail.com>



On 2016年12月22日 02:46, Nicolai Hähnle wrote:
> +static inline bool __sched
> +__ww_ctx_stamp_after(struct ww_acquire_ctx *a, struct ww_acquire_ctx *b)
> +{
> +	return a->stamp - b->stamp <= LONG_MAX &&
> +	       (a->stamp != b->stamp || a > b);
I want to ask a stupid question, why a can compare with b? They are 
pointers of structure. Isn't stamp enough for compare?

Thanks,
David Zhou
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dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

WARNING: multiple messages have this Message-ID (diff)
From: zhoucm1 <david1.zhou@amd.com>
To: "Nicolai Hähnle" <nhaehnle@gmail.com>, linux-kernel@vger.kernel.org
Cc: "Maarten Lankhorst" <dev@mblankhorst.nl>,
	"Nicolai Hähnle" <Nicolai.Haehnle@amd.com>,
	"Peter Zijlstra" <peterz@infradead.org>,
	dri-devel@lists.freedesktop.org, "Ingo Molnar" <mingo@redhat.com>
Subject: Re: [PATCH v3 03/12] locking/ww_mutex: Extract stamp comparison to __ww_mutex_stamp_after
Date: Thu, 22 Dec 2016 09:58:30 +0800	[thread overview]
Message-ID: <585B3346.2020001@amd.com> (raw)
In-Reply-To: <1482346000-9927-4-git-send-email-nhaehnle@gmail.com>



On 2016年12月22日 02:46, Nicolai Hähnle wrote:
> +static inline bool __sched
> +__ww_ctx_stamp_after(struct ww_acquire_ctx *a, struct ww_acquire_ctx *b)
> +{
> +	return a->stamp - b->stamp <= LONG_MAX &&
> +	       (a->stamp != b->stamp || a > b);
I want to ask a stupid question, why a can compare with b? They are 
pointers of structure. Isn't stamp enough for compare?

Thanks,
David Zhou

  reply	other threads:[~2016-12-22  2:15 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-21 18:46 [PATCH v3 00/12] locking/ww_mutex: Keep sorted wait list to avoid stampedes Nicolai Hähnle
2016-12-21 18:46 ` [PATCH v3 01/12] drm/vgem: Use ww_mutex_(un)lock even with a NULL context Nicolai Hähnle
2016-12-21 18:46   ` Nicolai Hähnle
2016-12-21 18:46 ` [PATCH v3 02/12] locking/mutex: Fix a race with handoffs and interruptible waits Nicolai Hähnle
2016-12-21 18:46 ` [PATCH v3 03/12] locking/ww_mutex: Extract stamp comparison to __ww_mutex_stamp_after Nicolai Hähnle
2016-12-21 18:46   ` Nicolai Hähnle
2016-12-22  1:58   ` zhoucm1 [this message]
2016-12-22  1:58     ` zhoucm1
2016-12-22  8:43     ` Nicolai Hähnle
2016-12-22  8:43       ` Nicolai Hähnle
2016-12-21 18:46 ` [PATCH v3 04/12] locking/ww_mutex: Set use_ww_ctx even when locking without a context Nicolai Hähnle
2016-12-21 18:46   ` Nicolai Hähnle
2016-12-21 18:46 ` [PATCH v3 05/12] locking/ww_mutex: Remove the __ww_mutex_lock inline wrappers Nicolai Hähnle
2016-12-23 10:48   ` Peter Zijlstra
2016-12-23 10:48     ` Peter Zijlstra
2016-12-23 11:16     ` Nicolai Hähnle
2016-12-23 12:13       ` Peter Zijlstra
2016-12-23 12:13         ` Peter Zijlstra
2016-12-21 18:46 ` [PATCH v3 06/12] locking/ww_mutex: Add waiters in stamp order Nicolai Hähnle
2016-12-21 18:46   ` Nicolai Hähnle
2016-12-21 18:46 ` [PATCH v3 07/12] locking/ww_mutex: Notify waiters that have to back off while adding tasks to wait list Nicolai Hähnle
2016-12-21 18:46 ` [PATCH v3 08/12] locking/ww_mutex: Wake at most one waiter for back off when acquiring the lock Nicolai Hähnle
2016-12-21 18:46 ` [PATCH v3 09/12] locking/ww_mutex: Re-check ww->ctx in the inner optimistic spin loop Nicolai Hähnle
2016-12-21 18:46 ` [PATCH v3 10/12] locking/ww_mutex: Yield to other waiters from optimistic spin Nicolai Hähnle
2016-12-21 18:46   ` Nicolai Hähnle
2017-01-05 17:47   ` Peter Zijlstra
2017-01-05 17:47     ` Peter Zijlstra
2016-12-21 18:46 ` [PATCH v3 11/12] locking/mutex: Initialize mutex_waiter::ww_ctx with poison when debugging Nicolai Hähnle
2016-12-21 18:46 ` [PATCH v3 12/12] Documentation/locking/ww_mutex: Update the design document Nicolai Hähnle

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