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From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Michal Hocko <mhocko@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Chris Metcalf <chris.d.metcalf@gmail.com>,
	Rusty Russell <rusty@rustcorp.com.au>,
	linux-mm@kvack.org, Guenter Roeck <linux@roeck-us.net>
Subject: Re: [PATCH] mm/swap.c: workaround for_each_cpu() bug on UP kernel.
Date: Tue, 12 Feb 2019 19:25:46 +0900	[thread overview]
Message-ID: <82168e14-8a89-e6ac-1756-e473e9c21616@i-love.sakura.ne.jp> (raw)
In-Reply-To: <20190212101109.GB7584@dhcp22.suse.cz>

On 2019/02/12 19:11, Michal Hocko wrote:
> This patch is ugly as hell! I do agree that for_each_cpu not working on
> CONFIG_SMP=n sucks but why do we even care about lru_add_drain_all when
> there is a single cpu? Why don't we simply do
> 
> diff --git a/mm/swap.c b/mm/swap.c
> index aa483719922e..952f24b09070 100644
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -660,6 +660,7 @@ static void lru_add_drain_per_cpu(struct work_struct *dummy)
>  
>  static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work);
>  
> +#ifdef CONFIG_SMP
>  /*
>   * Doesn't need any cpu hotplug locking because we do rely on per-cpu
>   * kworkers being shut down before our page_alloc_cpu_dead callback is
> @@ -702,6 +703,10 @@ void lru_add_drain_all(void)
>  
>  	mutex_unlock(&lock);
>  }
> +#else
> +#define lru_add_drain_all() lru_add_drain()
> +
> +#endif

If there is no need to evaluate the "if" conditions, I'm fine with this shortcut.


  reply	other threads:[~2019-02-12 10:25 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-07  9:53 Tetsuo Handa
2019-02-07 14:07 ` Guenter Roeck
2019-02-07 14:18 ` William Kucharski
2019-02-12 10:11 ` Michal Hocko
2019-02-12 10:25   ` Tetsuo Handa [this message]
2019-02-12 11:21     ` Michal Hocko
2019-02-12 11:29       ` Michal Hocko
2019-02-12 11:37         ` Tetsuo Handa
2019-02-12 21:06         ` Andrew Morton
2019-02-13 12:43           ` Michal Hocko
2019-02-13 21:37             ` Andrew Morton
2019-02-12 23:19         ` [PATCH] mm: handle lru_add_drain_all for UP properly kbuild test robot
2019-02-12 23:48         ` kbuild test robot

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