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authorTejun Heo <tj@kernel.org>2016-09-16 15:49:32 -0400
committerTejun Heo <tj@kernel.org>2016-09-17 13:18:21 -0400
commit3347fa0928210d96aaa2bd6cd5a8391d5e630873 (patch)
tree6b2b82cee1af9a916679e9713878ceaf81d13e45 /include/linux/workqueue.h
parentfa07fb6a4ecad41d373eaf1574b9d54b4f0c1e75 (diff)
workqueue: make workqueue available early during boot
Workqueue is currently initialized in an early init call; however, there are cases where early boot code has to be split and reordered to come after workqueue initialization or the same code path which makes use of workqueues is used both before workqueue initailization and after. The latter cases have to gate workqueue usages with keventd_up() tests, which is nasty and easy to get wrong. Workqueue usages have become widespread and it'd be a lot more convenient if it can be used very early from boot. This patch splits workqueue initialization into two steps. workqueue_init_early() which sets up the basic data structures so that workqueues can be created and work items queued, and workqueue_init() which actually brings up workqueues online and starts executing queued work items. The former step can be done very early during boot once memory allocation, cpumasks and idr are initialized. The latter right after kthreads become available. This allows work item queueing and canceling from very early boot which is what most of these use cases want. * As systemd_wq being initialized doesn't indicate that workqueue is fully online anymore, update keventd_up() to test wq_online instead. The follow-up patches will get rid of all its usages and the function itself. * Flushing doesn't make sense before workqueue is fully initialized. The flush functions trigger WARN and return immediately before fully online. * Work items are never in-flight before fully online. Canceling can always succeed by skipping the flush step. * Some code paths can no longer assume to be called with irq enabled as irq is disabled during early boot. Use irqsave/restore operations instead. v2: Watchdog init, which requires timer to be running, moved from workqueue_init_early() to workqueue_init(). Signed-off-by: Tejun Heo <tj@kernel.org> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/CA+55aFx0vPuMuxn00rBSM192n-Du5uxy+4AvKa0SBSOVJeuCGg@mail.gmail.com
Diffstat (limited to 'include/linux/workqueue.h')
-rw-r--r--include/linux/workqueue.h7
1 files changed, 6 insertions, 1 deletions
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 26cc1df280d6..91d416f9c0a7 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -358,6 +358,8 @@ extern struct workqueue_struct *system_freezable_wq;
extern struct workqueue_struct *system_power_efficient_wq;
extern struct workqueue_struct *system_freezable_power_efficient_wq;
+extern bool wq_online;
+
extern struct workqueue_struct *
__alloc_workqueue_key(const char *fmt, unsigned int flags, int max_active,
struct lock_class_key *key, const char *lock_name, ...) __printf(1, 6);
@@ -594,7 +596,7 @@ static inline bool schedule_delayed_work(struct delayed_work *dwork,
*/
static inline bool keventd_up(void)
{
- return system_wq != NULL;
+ return wq_online;
}
#ifndef CONFIG_SMP
@@ -631,4 +633,7 @@ int workqueue_online_cpu(unsigned int cpu);
int workqueue_offline_cpu(unsigned int cpu);
#endif
+int __init workqueue_init_early(void);
+int __init workqueue_init(void);
+
#endif