From b31041042a8cdece67f925e4bae55b5f5fd754ca Mon Sep 17 00:00:00 2001 From: Lai Jiangshan Date: Tue, 19 Feb 2013 12:17:02 -0800 Subject: workqueue: better define synchronization rule around rescuer->pool updates Rescuers visit different worker_pools to process work items from pools under pressure. Currently, rescuer->pool is updated outside any locking and when an outsider looks at a rescuer, there's no way to tell when and whether rescuer->pool is gonna change. While this doesn't currently cause any problem, it is nasty. With recent worker_maybe_bind_and_lock() changes, we can move rescuer->pool updates inside pool locks such that if rescuer->pool equals a locked pool, it's guaranteed to stay that way until the pool is unlocked. Move rescuer->pool inside pool->lock. This patch doesn't introduce any visible behavior difference. tj: Updated the description. Signed-off-by: Lai Jiangshan Signed-off-by: Tejun Heo --- kernel/workqueue.c | 3 ++- kernel/workqueue_internal.h | 1 + 2 files changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 09545d445a55..fd9a28a13afd 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -2357,8 +2357,8 @@ repeat: mayday_clear_cpu(cpu, wq->mayday_mask); /* migrate to the target cpu if possible */ - rescuer->pool = pool; worker_maybe_bind_and_lock(pool); + rescuer->pool = pool; /* * Slurp in all works issued via this workqueue and @@ -2379,6 +2379,7 @@ repeat: if (keep_working(pool)) wake_up_worker(pool); + rescuer->pool = NULL; spin_unlock_irq(&pool->lock); } diff --git a/kernel/workqueue_internal.h b/kernel/workqueue_internal.h index 07650264ec15..f9c887731e2b 100644 --- a/kernel/workqueue_internal.h +++ b/kernel/workqueue_internal.h @@ -32,6 +32,7 @@ struct worker { struct list_head scheduled; /* L: scheduled works */ struct task_struct *task; /* I: worker task */ struct worker_pool *pool; /* I: the associated pool */ + /* L: for rescuers */ /* 64 bytes boundary on 64bit, 32 on 32bit */ unsigned long last_active; /* L: last active timestamp */ unsigned int flags; /* X: flags */ -- cgit