workers' concurrency setting need to be coordinate with pool's concurrency setting when create_worker()/destroy_worker()/cpu_inline() cpu_offline().
But create_worker() handles it non-atomically(not in a single pool->lock). This patch makes the behavior atomically. Now bind_list is used for coordinating workers' cpumask with the pool. worker_idr is used for coordinating workers' concurrency with the pool. cpumask is coordinated at first and then concurrency. We don't want to remove worker_idr and re-use bind_list. if we do so: 1) the locking will become much complex. 2) after removing worker_idr, we need to add a ida back we do not save any thing. Signed-off-by: Lai Jiangshan <[email protected]> --- kernel/workqueue.c | 15 +++------------ 1 files changed, 3 insertions(+), 12 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 6c38aed..3a6be02 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -63,10 +63,6 @@ enum { * While DISASSOCIATED, the cpu may be offline and all workers have * %WORKER_UNBOUND set and concurrency management disabled, and may * be executing on any CPU. The pool behaves as an unbound one. - * - * Note that DISASSOCIATED should be flipped only while holding - * manager_mutex to avoid changing binding state while - * create_worker() is in progress. */ POOL_MANAGE_WORKERS = 1 << 0, /* need to manage workers */ POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */ @@ -1745,16 +1741,10 @@ static struct worker *create_worker(struct worker_pool *pool) bind_worker(worker, pool); - /* - * The caller is responsible for ensuring %POOL_DISASSOCIATED - * remains stable across this function. See the comments above the - * flag definition for details. - */ + /* successful, commit the worker to the pool's concurrency setting */ + spin_lock_irq(&pool->lock); if (pool->flags & POOL_DISASSOCIATED) worker->flags |= WORKER_UNBOUND; - - /* successful, commit the pointer to idr */ - spin_lock_irq(&pool->lock); idr_replace(&pool->worker_idr, worker, worker->id); spin_unlock_irq(&pool->lock); @@ -1841,6 +1831,7 @@ static void destroy_worker(struct worker *worker) list_del_init(&worker->entry); worker->flags |= WORKER_DIE; + /* release @id and leave pool's concurrency setting */ idr_remove(&pool->worker_idr, worker->id); wake_up_process(worker->task); } -- 1.7.4.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
