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authorTejun Heo <tj@kernel.org>2023-08-07 15:57:22 -1000
committerTejun Heo <tj@kernel.org>2023-08-07 15:57:22 -1000
commitbc8b50c2dfac946c1beed782c1823e52cf55a352 (patch)
treefed2c448bbef1ece384d2ec2e0528aa5368b92cb
parent87437656c24341ab8782c29a7d5f4525bb70a62d (diff)
workqueue: Drop the special locking rule for worker->flags and worker_pool->flags
worker->flags used to be accessed from scheduler hooks without grabbing pool->lock for concurrency management. This is no longer true since 6d25be5782e4 ("sched/core, workqueues: Distangle worker accounting from rq lock"). Also, it's unclear why worker_pool->flags was using the "X" rule. All relevant users are accessing it under the pool lock. Let's drop the special "X" rule and use the "L" rule for these flag fields instead. While at it, replace the CONTEXT comment with lockdep_assert_held(). This allows worker_set/clr_flags() to be used from context which isn't the worker itself. This will be used later to implement assinging work items to workers before waking them up so that workqueue can have better control over which worker executes which work item on which CPU. The only actual changes are sanity checks. There shouldn't be any visible behavior changes. Signed-off-by: Tejun Heo <tj@kernel.org>
-rw-r--r--kernel/workqueue.c17
-rw-r--r--kernel/workqueue_internal.h2
2 files changed, 4 insertions, 15 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index ae975a7c9f69..598009ad97d1 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -122,11 +122,6 @@ enum {
*
* L: pool->lock protected. Access with pool->lock held.
*
- * X: During normal operation, modification requires pool->lock and should
- * be done only from local cpu. Either disabling preemption on local
- * cpu or grabbing pool->lock is enough for read access. If
- * POOL_DISASSOCIATED is set, it's identical to L.
- *
* K: Only modified by worker while holding pool->lock. Can be safely read by
* self, while holding pool->lock or from IRQ context if %current is the
* kworker.
@@ -160,7 +155,7 @@ struct worker_pool {
int cpu; /* I: the associated cpu */
int node; /* I: the associated node ID */
int id; /* I: pool ID */
- unsigned int flags; /* X: flags */
+ unsigned int flags; /* L: flags */
unsigned long watchdog_ts; /* L: watchdog timestamp */
bool cpu_stall; /* WD: stalled cpu bound pool */
@@ -910,15 +905,12 @@ static void wake_up_worker(struct worker_pool *pool)
* @flags: flags to set
*
* Set @flags in @worker->flags and adjust nr_running accordingly.
- *
- * CONTEXT:
- * raw_spin_lock_irq(pool->lock)
*/
static inline void worker_set_flags(struct worker *worker, unsigned int flags)
{
struct worker_pool *pool = worker->pool;
- WARN_ON_ONCE(worker->task != current);
+ lockdep_assert_held(&pool->lock);
/* If transitioning into NOT_RUNNING, adjust nr_running. */
if ((flags & WORKER_NOT_RUNNING) &&
@@ -935,16 +927,13 @@ static inline void worker_set_flags(struct worker *worker, unsigned int flags)
* @flags: flags to clear
*
* Clear @flags in @worker->flags and adjust nr_running accordingly.
- *
- * CONTEXT:
- * raw_spin_lock_irq(pool->lock)
*/
static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
{
struct worker_pool *pool = worker->pool;
unsigned int oflags = worker->flags;
- WARN_ON_ONCE(worker->task != current);
+ lockdep_assert_held(&pool->lock);
worker->flags &= ~flags;
diff --git a/kernel/workqueue_internal.h b/kernel/workqueue_internal.h
index 6b1d66e28269..f6275944ada7 100644
--- a/kernel/workqueue_internal.h
+++ b/kernel/workqueue_internal.h
@@ -48,7 +48,7 @@ struct worker {
/* A: runs through worker->node */
unsigned long last_active; /* K: last active timestamp */
- unsigned int flags; /* X: flags */
+ unsigned int flags; /* L: flags */
int id; /* I: worker id */
/*