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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: linux-mm@kvack.org, tglx@linutronix.de,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 2/3] mm: workingset: make shadow_lru_isolate() use locking suffix
Date: Tue, 26 Jun 2018 23:25:34 +0200	[thread overview]
Message-ID: <20180626212534.sp4p76gcvldcai57@linutronix.de> (raw)
In-Reply-To: <20180624195753.2e277k5xhujypwre@esperanza>

On 2018-06-24 22:57:53 [+0300], Vladimir Davydov wrote:
> On Fri, Jun 22, 2018 at 05:12:20PM +0200, Sebastian Andrzej Siewior wrote:
> > shadow_lru_isolate() disables interrupts and acquires a lock. It could
> > use spin_lock_irq() instead. It also uses local_irq_enable() while it
> > could use spin_unlock_irq()/xa_unlock_irq().
> > 
> > Use proper suffix for lock/unlock in order to enable/disable interrupts
> > during release/acquire of a lock.
> > 
> > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> 
> I don't like when a spin lock is locked with local_irq_disabled +
> spin_lock and unlocked with spin_unlock_irq - it looks asymmetric.
> IMHO the code is pretty easy to follow as it is - local_irq_disable in
> scan_shadow_nodes matches local_irq_enable in shadow_lru_isolate.

it is not asymmetric because a later patch makes it use spin_lock_irq(),
too. If you use local_irq_disable() and a spin_lock() (like you suggest
in 3/3 as well) then you separate the locking instruction. It works as
expected on vanilla but break other locking implementations like those
on RT. Also if the locking changes then the local_irq_disable() part
will be forgotten like you saw in 1/3 of this series.

Sebastian

  reply	other threads:[~2018-06-26 21:25 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-22 15:12 [PATCH 0/3] mm: use irq locking suffix instead local_irq_disable() Sebastian Andrzej Siewior
2018-06-22 15:12 ` [PATCH 1/3] mm: workingset: remove local_irq_disable() from count_shadow_nodes() Sebastian Andrzej Siewior
2018-06-24 19:51   ` Vladimir Davydov
2018-06-25 10:36   ` Kirill Tkhai
2018-06-22 15:12 ` [PATCH 2/3] mm: workingset: make shadow_lru_isolate() use locking suffix Sebastian Andrzej Siewior
2018-06-24 19:57   ` Vladimir Davydov
2018-06-26 21:25     ` Sebastian Andrzej Siewior [this message]
2018-06-27  8:50       ` Vladimir Davydov
2018-06-27  9:20         ` Sebastian Andrzej Siewior
2018-06-28  9:30           ` Vladimir Davydov
2018-07-02 22:38             ` Sebastian Andrzej Siewior
2018-06-22 15:12 ` [PATCH 3/3] mm: list_lru: Add lock_irq member to __list_lru_init() Sebastian Andrzej Siewior
2018-06-24 20:09   ` Vladimir Davydov
2018-07-03 14:52     ` Sebastian Andrzej Siewior
2018-07-03 14:52       ` [PATCH 1/4] mm/list_lru: use list_lru_walk_one() in list_lru_walk_node() Sebastian Andrzej Siewior
2018-07-03 14:52       ` [PATCH 2/4] mm/list_lru: Move locking from __list_lru_walk_one() to its caller Sebastian Andrzej Siewior
2018-07-03 14:52       ` [PATCH 3/4] mm/list_lru: Pass struct list_lru_node as an argument __list_lru_walk_one() Sebastian Andrzej Siewior
2018-07-03 14:52       ` [PATCH 4/4] mm/list_lru: Introduce list_lru_shrink_walk_irq() Sebastian Andrzej Siewior
2018-07-03 21:14       ` Andrew Morton
2018-07-03 21:44         ` Re: Sebastian Andrzej Siewior
2018-07-04 14:44           ` Re: Vladimir Davydov
2018-06-22 21:39 ` [PATCH 0/3] mm: use irq locking suffix instead local_irq_disable() Andrew Morton
2018-06-24 20:10   ` Vladimir Davydov

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