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From: Michal Hocko <mhocko@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Tejun Heo <tj@kernel.org>, Peter Zijlstra <peterz@infradead.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Mel Gorman <mgorman@suse.de>,
	linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm: drop hotplug lock from lru_add_drain_all
Date: Tue, 14 Nov 2017 15:32:00 +0100	[thread overview]
Message-ID: <20171114143200.brmgskoqxjlrhrzx@dhcp22.suse.cz> (raw)
In-Reply-To: <20171114142347.syzyd6tlnpe2afur@dhcp22.suse.cz>

On Tue 14-11-17 15:23:47, Michal Hocko wrote:
[...]
> +/*
> + * 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
> + * executed on the offlined cpu
> + */
>  void lru_add_drain_all(void)
>  {
>  	static DEFINE_MUTEX(lock);

Ble the part of the comment didn't go through

diff --git a/mm/swap.c b/mm/swap.c
index 8bfdcab9f83e..1ab8122d2d0c 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -688,6 +688,13 @@ static void lru_add_drain_per_cpu(struct work_struct *dummy)
 
 static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work);
 
+/*
+ * 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
+ * executed on the offlined cpu.
+ * Calling this function with cpu hotplug locks held can actually lead
+ * to obscure indirect dependencies via WQ context.
+ */
 void lru_add_drain_all(void)
 {
 	static DEFINE_MUTEX(lock);
-- 
Michal Hocko
SUSE Labs

WARNING: multiple messages have this Message-ID
From: Michal Hocko <mhocko@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Tejun Heo <tj@kernel.org>, Peter Zijlstra <peterz@infradead.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Mel Gorman <mgorman@suse.de>,
	linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm: drop hotplug lock from lru_add_drain_all
Date: Tue, 14 Nov 2017 15:32:00 +0100	[thread overview]
Message-ID: <20171114143200.brmgskoqxjlrhrzx@dhcp22.suse.cz> (raw)
In-Reply-To: <20171114142347.syzyd6tlnpe2afur@dhcp22.suse.cz>

On Tue 14-11-17 15:23:47, Michal Hocko wrote:
[...]
> +/*
> + * 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
> + * executed on the offlined cpu
> + */
>  void lru_add_drain_all(void)
>  {
>  	static DEFINE_MUTEX(lock);

Ble the part of the comment didn't go through

diff --git a/mm/swap.c b/mm/swap.c
index 8bfdcab9f83e..1ab8122d2d0c 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -688,6 +688,13 @@ static void lru_add_drain_per_cpu(struct work_struct *dummy)
 
 static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work);
 
+/*
+ * 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
+ * executed on the offlined cpu.
+ * Calling this function with cpu hotplug locks held can actually lead
+ * to obscure indirect dependencies via WQ context.
+ */
 void lru_add_drain_all(void)
 {
 	static DEFINE_MUTEX(lock);
-- 
Michal Hocko
SUSE Labs

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  reply	other threads:[~2017-11-14 14:32 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-11-14 13:53 Michal Hocko
2017-11-14 13:53 ` Michal Hocko
2017-11-14 14:13 ` Thomas Gleixner
2017-11-14 14:13   ` Thomas Gleixner
2017-11-14 14:23   ` Michal Hocko
2017-11-14 14:23     ` Michal Hocko
2017-11-14 14:32     ` Michal Hocko [this message]
2017-11-14 14:32       ` Michal Hocko
2017-11-14 15:05       ` Thomas Gleixner
2017-11-14 15:05         ` Thomas Gleixner
2017-11-14 15:11         ` Thomas Gleixner
2017-11-14 15:11           ` Thomas Gleixner
2017-11-14 15:14         ` Michal Hocko
2017-11-14 15:14           ` Michal Hocko
2017-11-16 12:05 Michal Hocko
2017-11-16 12:05 ` Michal Hocko

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