From 27d4ee03078aba88c5e07dcc4917e8d01d046f38 Mon Sep 17 00:00:00 2001 From: Lukas Wunner Date: Sun, 11 Feb 2018 10:38:28 +0100 Subject: [PATCH] workqueue: Allow retrieval of current task's work struct Introduce a helper to retrieve the current task's work struct if it is a workqueue worker. This allows us to fix a long-standing deadlock in several DRM drivers wherein the ->runtime_suspend callback waits for a specific worker to finish and that worker in turn calls a function which waits for runtime suspend to finish. That function is invoked from multiple call sites and waiting for runtime suspend to finish is the correct thing to do except if it's executing in the context of the worker. Cc: Lai Jiangshan Cc: Dave Airlie Cc: Ben Skeggs Cc: Alex Deucher Acked-by: Tejun Heo Reviewed-by: Lyude Paul Signed-off-by: Lukas Wunner Link: https://patchwork.freedesktop.org/patch/msgid/2d8f603074131eb87e588d2b803a71765bd3a2fd.1518338788.git.lukas@wunner.de --- include/linux/workqueue.h | 1 + kernel/workqueue.c | 16 ++++++++++++++++ 2 files changed, 17 insertions(+) diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h index 4a54ef9..bc0cda1 100644 --- a/include/linux/workqueue.h +++ b/include/linux/workqueue.h @@ -465,6 +465,7 @@ extern bool cancel_delayed_work_sync(struct delayed_work *dwork); extern void workqueue_set_max_active(struct workqueue_struct *wq, int max_active); +extern struct work_struct *current_work(void); extern bool current_is_workqueue_rescuer(void); extern bool workqueue_congested(int cpu, struct workqueue_struct *wq); extern unsigned int work_busy(struct work_struct *work); diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 43d18cb..255c20e 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -4168,6 +4168,22 @@ void workqueue_set_max_active(struct workqueue_struct *wq, int max_active) EXPORT_SYMBOL_GPL(workqueue_set_max_active); /** + * current_work - retrieve %current task's work struct + * + * Determine if %current task is a workqueue worker and what it's working on. + * Useful to find out the context that the %current task is running in. + * + * Return: work struct if %current task is a workqueue worker, %NULL otherwise. + */ +struct work_struct *current_work(void) +{ + struct worker *worker = current_wq_worker(); + + return worker ? worker->current_work : NULL; +} +EXPORT_SYMBOL(current_work); + +/** * current_is_workqueue_rescuer - is %current workqueue rescuer? * * Determine whether %current is a workqueue rescuer. Can be used from -- 2.7.4