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Subject[PATCH 3/9] workqueue: ROGUE workers are UNBOUND workers
Date
Currently, WORKER_UNBOUND is used to mark workers for the unbound
global_cwq and WORKER_ROGUE is used to mark workers for disassociated
per-cpu global_cwqs. Both are used to make the marked worker skip
concurrency management and the only place they make any difference is
in worker_enter_idle() where WORKER_ROGUE is used to skip scheduling
idle timer, which can easily be replaced with trustee state testing.

This patch replaces WORKER_ROGUE with WORKER_UNBOUND and drops
WORKER_ROGUE. This is to prepare for removing trustee and handling
disassociated global_cwqs as unbound.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
kernel/workqueue.c | 46 +++++++++++++++++++++-------------------------
1 files changed, 21 insertions(+), 25 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 1405fb9..af51292 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -58,13 +58,12 @@ enum {
WORKER_DIE = 1 << 1, /* die die die */
WORKER_IDLE = 1 << 2, /* is idle */
WORKER_PREP = 1 << 3, /* preparing to run works */
- WORKER_ROGUE = 1 << 4, /* not bound to any cpu */
WORKER_REBIND = 1 << 5, /* mom is home, come back */
WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */
WORKER_UNBOUND = 1 << 7, /* worker is unbound */

- WORKER_NOT_RUNNING = WORKER_PREP | WORKER_ROGUE | WORKER_REBIND |
- WORKER_CPU_INTENSIVE | WORKER_UNBOUND,
+ WORKER_NOT_RUNNING = WORKER_PREP | WORKER_REBIND | WORKER_UNBOUND |
+ WORKER_CPU_INTENSIVE,

/* gcwq->trustee_state */
TRUSTEE_START = 0, /* start */
@@ -1198,7 +1197,7 @@ static void worker_enter_idle(struct worker *worker)
/* idle_list is LIFO */
list_add(&worker->entry, &pool->idle_list);

- if (likely(!(worker->flags & WORKER_ROGUE))) {
+ if (likely(gcwq->trustee_state != TRUSTEE_DONE)) {
if (too_many_workers(pool) && !timer_pending(&pool->idle_timer))
mod_timer(&pool->idle_timer,
jiffies + IDLE_WORKER_TIMEOUT);
@@ -1207,7 +1206,7 @@ static void worker_enter_idle(struct worker *worker)

/*
* Sanity check nr_running. Because trustee releases gcwq->lock
- * between setting %WORKER_ROGUE and zapping nr_running, the
+ * between setting %WORKER_UNBOUND and zapping nr_running, the
* warning may trigger spuriously. Check iff trustee is idle.
*/
WARN_ON_ONCE(gcwq->trustee_state == TRUSTEE_DONE &&
@@ -1301,10 +1300,10 @@ __acquires(&gcwq->lock)
}

/*
- * Function for worker->rebind_work used to rebind rogue busy workers
- * to the associated cpu which is coming back online. This is
- * scheduled by cpu up but can race with other cpu hotplug operations
- * and may be executed twice without intervening cpu down.
+ * Function for worker->rebind_work used to rebind unbound busy workers to
+ * the associated cpu which is coming back online. This is scheduled by
+ * cpu up but can race with other cpu hotplug operations and may be
+ * executed twice without intervening cpu down.
*/
static void worker_rebind_fn(struct work_struct *work)
{
@@ -1385,9 +1384,8 @@ static struct worker *create_worker(struct worker_pool *pool, bool bind)
set_user_nice(worker->task, HIGHPRI_NICE_LEVEL);

/*
- * A rogue worker will become a regular one if CPU comes
- * online later on. Make sure every worker has
- * PF_THREAD_BOUND set.
+ * An unbound worker will become a regular one if CPU comes online
+ * later on. Make sure every worker has PF_THREAD_BOUND set.
*/
if (bind && !on_unbound_cpu)
kthread_bind(worker->task, gcwq->cpu);
@@ -3215,11 +3213,10 @@ EXPORT_SYMBOL_GPL(work_busy);
* gcwqs serve mix of short, long and very long running works making
* blocked draining impractical.
*
- * This is solved by allowing a gcwq to be detached from CPU, running
- * it with unbound (rogue) workers and allowing it to be reattached
- * later if the cpu comes back online. A separate thread is created
- * to govern a gcwq in such state and is called the trustee of the
- * gcwq.
+ * This is solved by allowing a gcwq to be detached from CPU, running it
+ * with unbound workers and allowing it to be reattached later if the cpu
+ * comes back online. A separate thread is created to govern a gcwq in
+ * such state and is called the trustee of the gcwq.
*
* Trustee states and their descriptions.
*
@@ -3359,19 +3356,18 @@ static int __cpuinit trustee_thread(void *__gcwq)
pool->flags |= POOL_MANAGING_WORKERS;

list_for_each_entry(worker, &pool->idle_list, entry)
- worker->flags |= WORKER_ROGUE;
+ worker->flags |= WORKER_UNBOUND;
}

for_each_busy_worker(worker, i, pos, gcwq)
- worker->flags |= WORKER_ROGUE;
+ worker->flags |= WORKER_UNBOUND;

gcwq->flags |= GCWQ_DISASSOCIATED;

/*
- * Call schedule() so that we cross rq->lock and thus can
- * guarantee sched callbacks see the rogue flag. This is
- * necessary as scheduler callbacks may be invoked from other
- * cpus.
+ * Call schedule() so that we cross rq->lock and thus can guarantee
+ * sched callbacks see the unbound flag. This is necessary as
+ * scheduler callbacks may be invoked from other cpus.
*/
spin_unlock_irq(&gcwq->lock);
schedule();
@@ -3439,7 +3435,7 @@ static int __cpuinit trustee_thread(void *__gcwq)
worker = create_worker(pool, false);
spin_lock_irq(&gcwq->lock);
if (worker) {
- worker->flags |= WORKER_ROGUE;
+ worker->flags |= WORKER_UNBOUND;
start_worker(worker);
}
}
@@ -3488,7 +3484,7 @@ static int __cpuinit trustee_thread(void *__gcwq)
* rebinding is scheduled.
*/
worker->flags |= WORKER_REBIND;
- worker->flags &= ~WORKER_ROGUE;
+ worker->flags &= ~WORKER_UNBOUND;

/* queue rebind_work, wq doesn't matter, use the default one */
if (test_and_set_bit(WORK_STRUCT_PENDING_BIT,
--
1.7.7.3


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