linux-kernel - Re: [PATCH 14/14] workqueue: use mod_delayed

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Message-ID: <8393.1344864477@warthog.procyon.org.uk>
Date:	Mon, 13 Aug 2012 14:27:57 +0100
From:	David Howells <dhowells@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	dhowells@...hat.com, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	padovan@...fusion.mobi, marcel@...tmann.org, peterz@...radead.org,
	mingo@...hat.com, davem@...emloft.net, dougthompson@...ssion.com,
	ibm-acpi@....eng.br, cbou@...l.ru, rui.zhang@...el.com,
	tomi.valkeinen@...com, Jens Axboe <axboe@...nel.dk>,
	Jiri Kosina <jkosina@...e.cz>, David Airlie <airlied@...ux.ie>,
	Roland Dreier <roland@...nel.org>,
	"John W. Linville" <linville@...driver.com>,
	Len Brown <len.brown@...el.com>,
	"J. Bruce Fields" <bfields@...ldses.org>,
	Johannes Berg <johannes@...solutions.net>
Subject: Re: [PATCH 14/14] workqueue: use mod_delayed_work() instead of cancel + queue

Tejun Heo <tj@...nel.org> wrote:

> Convert delayed_work users doing cancel_delayed_work() followed by
> queue_delayed_work() to mod_delayed_work().
> 
> Most conversions are straight-forward.  Ones worth mentioning are,
> 
> * drivers/edac/edac_mc.c: edac_mc_workq_setup() converted to always
>   use mod_delayed_work() and cancel loop in
>   edac_mc_reset_delay_period() is dropped.
> 
> * drivers/platform/x86/thinkpad_acpi.c: No need to remember whether
>   watchdog is active or not.  @fan_watchdog_active and related code
>   dropped.
> 
> * drivers/power/charger-manager.c: Seemingly a lot of
>   delayed_work_pending() abuse going on here.
>   [delayed_]work_pending() are unsynchronized and racy when used like
>   this.  I converted one instance in fullbatt_handler().  Please
>   conver the rest so that it invokes workqueue APIs for the intended
>   target state rather than trying to game work item pending state
>   transitions.  e.g. if timer should be modified - call
>   mod_delayed_work(), canceled - call cancel_delayed_work[_sync]().
> 
> * drivers/thermal/thermal_sys.c: thermal_zone_device_set_polling()
>   simplified.  Note that round_jiffies() calls in this function are
>   meaningless.  round_jiffies() work on absolute jiffies not delta
>   delay used by delayed_work.
> 
> v2: Tomi pointed out that __cancel_delayed_work() users can't be
>     safely converted to mod_delayed_work().  They could be calling it
>     from irq context and if that happens while delayed_work_timer_fn()
>     is running, it could deadlock.  __cancel_delayed_work() users are
>     dropped.
> 
> Signed-off-by: Tejun Heo <tj@...nel.org>
> Acked-by: Henrique de Moraes Holschuh <hmh@....eng.br>
> Acked-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
> Acked-by: Anton Vorontsov <cbouatmailru@...il.com>

Acked-by: David Howells <dhowells@...hat.com>
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