Re: [PATCH 14/14] workqueue: use mod_delayed_work() instead of cancel + queue

[David Howells]

Tejun Heo <tj@xxxxxxxxxx> 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@xxxxxxxxxx>
> Acked-by: Henrique de Moraes Holschuh <hmh@xxxxxxxxxx>
> Acked-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
> Acked-by: Anton Vorontsov <cbouatmailru@xxxxxxxxx>

Acked-by: David Howells <dhowells@xxxxxxxxxx>
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