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workqueue: make GCWQ_DISASSOCIATED a pool flag

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Make GCWQ_DISASSOCIATED a pool flag POOL_DISASSOCIATED.  This patch
doesn't change locking - DISASSOCIATED on both pools of a CPU are set
or clear together while holding gcwq->lock.  It shouldn't cause any
functional difference.

This is part of an effort to remove global_cwq and make worker_pool
the top level abstraction, which in turn will help implementing worker
pools with user-specified attributes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
This commit is contained in:
Tejun Heo 2013-01-24 11:01:33 -08:00
parent e34cdddb03
commit 2464757086
1 changed files with 35 additions and 31 deletions
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66
kernel/workqueue.c
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@ -48,26 +48,28 @@
enum {
/*
* global_cwq flags
*/
GCWQ_FREEZING = 1 << 1, /* freeze in progress */
/*
* worker_pool flags
*
* A bound gcwq is either associated or disassociated with its CPU.
* A bound pool is either associated or disassociated with its CPU.
* While associated (!DISASSOCIATED), all workers are bound to the
* CPU and none has %WORKER_UNBOUND set and concurrency management
* is in effect.
*
* 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 gcwq behaves as an unbound one.
* be executing on any CPU. The pool behaves as an unbound one.
*
* Note that DISASSOCIATED can be flipped only while holding
* assoc_mutex of all pools on the gcwq to avoid changing binding
* state while create_worker() is in progress.
* assoc_mutex to avoid changing binding state while
* create_worker() is in progress.
*/
GCWQ_DISASSOCIATED = 1 << 0, /* cpu can't serve workers */
GCWQ_FREEZING = 1 << 1, /* freeze in progress */
/* pool flags */
POOL_MANAGE_WORKERS = 1 << 0, /* need to manage workers */
POOL_MANAGING_WORKERS = 1 << 1, /* managing workers */
POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
/* worker flags */
WORKER_STARTED = 1 << 0, /* started */
@ -115,7 +117,7 @@ enum {
* X: During normal operation, modification requires gcwq->lock and
* should be done only from local cpu. Either disabling preemption
* on local cpu or grabbing gcwq->lock is enough for read access.
* If GCWQ_DISASSOCIATED is set, it's identical to L.
* If POOL_DISASSOCIATED is set, it's identical to L.
*
* F: wq->flush_mutex protected.
*
@ -138,7 +140,7 @@ struct worker_pool {
struct timer_list idle_timer; /* L: worker idle timeout */
struct timer_list mayday_timer; /* L: SOS timer for workers */
struct mutex assoc_mutex; /* protect GCWQ_DISASSOCIATED */
struct mutex assoc_mutex; /* protect POOL_DISASSOCIATED */
struct ida worker_ida; /* L: for worker IDs */
};
@ -439,9 +441,9 @@ static DEFINE_PER_CPU(struct global_cwq, global_cwq);
static DEFINE_PER_CPU_SHARED_ALIGNED(atomic_t, pool_nr_running[NR_STD_WORKER_POOLS]);
/*
* Global cpu workqueue and nr_running counter for unbound gcwq. The
* gcwq is always online, has GCWQ_DISASSOCIATED set, and all its
* workers have WORKER_UNBOUND set.
* Global cpu workqueue and nr_running counter for unbound gcwq. The pools
* for online CPUs have POOL_DISASSOCIATED set, and all their workers have
* WORKER_UNBOUND set.
*/
static struct global_cwq unbound_global_cwq;
static atomic_t unbound_pool_nr_running[NR_STD_WORKER_POOLS] = {
@ -1474,7 +1476,6 @@ EXPORT_SYMBOL_GPL(mod_delayed_work);
static void worker_enter_idle(struct worker *worker)
{
struct worker_pool *pool = worker->pool;
struct global_cwq *gcwq = pool->gcwq;
BUG_ON(worker->flags & WORKER_IDLE);
BUG_ON(!list_empty(&worker->entry) &&
@ -1497,7 +1498,7 @@ static void worker_enter_idle(struct worker *worker)
* nr_running, the warning may trigger spuriously. Check iff
* unbind is not in progress.
*/
WARN_ON_ONCE(!(gcwq->flags & GCWQ_DISASSOCIATED) &&
WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) &&
pool->nr_workers == pool->nr_idle &&
atomic_read(get_pool_nr_running(pool)));
}
@ -1538,7 +1539,7 @@ static void worker_leave_idle(struct worker *worker)
* [dis]associated in the meantime.
*
* This function tries set_cpus_allowed() and locks gcwq and verifies the
* binding against %GCWQ_DISASSOCIATED which is set during
* binding against %POOL_DISASSOCIATED which is set during
* %CPU_DOWN_PREPARE and cleared during %CPU_ONLINE, so if the worker
* enters idle state or fetches works without dropping lock, it can
* guarantee the scheduling requirement described in the first paragraph.
@ -1554,7 +1555,8 @@ static void worker_leave_idle(struct worker *worker)
static bool worker_maybe_bind_and_lock(struct worker *worker)
__acquires(&gcwq->lock)
{
struct global_cwq *gcwq = worker->pool->gcwq;
struct worker_pool *pool = worker->pool;
struct global_cwq *gcwq = pool->gcwq;
struct task_struct *task = worker->task;
while (true) {
@ -1562,13 +1564,13 @@ __acquires(&gcwq->lock)
* The following call may fail, succeed or succeed
* without actually migrating the task to the cpu if
* it races with cpu hotunplug operation. Verify
* against GCWQ_DISASSOCIATED.
* against POOL_DISASSOCIATED.
*/
if (!(gcwq->flags & GCWQ_DISASSOCIATED))
if (!(pool->flags & POOL_DISASSOCIATED))
set_cpus_allowed_ptr(task, get_cpu_mask(gcwq->cpu));
spin_lock_irq(&gcwq->lock);
if (gcwq->flags & GCWQ_DISASSOCIATED)
if (pool->flags & POOL_DISASSOCIATED)
return false;
if (task_cpu(task) == gcwq->cpu &&
cpumask_equal(&current->cpus_allowed,
@ -1766,14 +1768,14 @@ static struct worker *create_worker(struct worker_pool *pool)
/*
* Determine CPU binding of the new worker depending on
* %GCWQ_DISASSOCIATED. The caller is responsible for ensuring the
* %POOL_DISASSOCIATED. The caller is responsible for ensuring the
* flag remains stable across this function. See the comments
* above the flag definition for details.
*
* As an unbound worker may later become a regular one if CPU comes
* online, make sure every worker has %PF_THREAD_BOUND set.
*/
if (!(gcwq->flags & GCWQ_DISASSOCIATED)) {
if (!(pool->flags & POOL_DISASSOCIATED)) {
kthread_bind(worker->task, gcwq->cpu);
} else {
worker->task->flags |= PF_THREAD_BOUND;
@ -2134,10 +2136,10 @@ __acquires(&gcwq->lock)
/*
* Ensure we're on the correct CPU. DISASSOCIATED test is
* necessary to avoid spurious warnings from rescuers servicing the
* unbound or a disassociated gcwq.
* unbound or a disassociated pool.
*/
WARN_ON_ONCE(!(worker->flags & WORKER_UNBOUND) &&
!(gcwq->flags & GCWQ_DISASSOCIATED) &&
!(pool->flags & POOL_DISASSOCIATED) &&
raw_smp_processor_id() != gcwq->cpu);
/*
@ -3472,7 +3474,7 @@ 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 disassociated from the CPU
* This is solved by allowing the pools to be disassociated from the CPU
* running as an unbound one and allowing it to be reattached later if the
* cpu comes back online.
*/
@ -3522,7 +3524,8 @@ static void gcwq_unbind_fn(struct work_struct *work)
for_each_busy_worker(worker, i, pos, gcwq)
worker->flags |= WORKER_UNBOUND;
gcwq->flags |= GCWQ_DISASSOCIATED;
for_each_worker_pool(pool, gcwq)
pool->flags |= POOL_DISASSOCIATED;
gcwq_release_assoc_and_unlock(gcwq);
@ -3581,7 +3584,8 @@ static int __cpuinit workqueue_cpu_up_callback(struct notifier_block *nfb,
case CPU_DOWN_FAILED:
case CPU_ONLINE:
gcwq_claim_assoc_and_lock(gcwq);
gcwq->flags &= ~GCWQ_DISASSOCIATED;
for_each_worker_pool(pool, gcwq)
pool->flags &= ~POOL_DISASSOCIATED;
rebind_workers(gcwq);
gcwq_release_assoc_and_unlock(gcwq);
break;
@ -3806,12 +3810,12 @@ static int __init init_workqueues(void)
spin_lock_init(&gcwq->lock);
gcwq->cpu = cpu;
gcwq->flags |= GCWQ_DISASSOCIATED;
hash_init(gcwq->busy_hash);
for_each_worker_pool(pool, gcwq) {
pool->gcwq = gcwq;
pool->flags |= POOL_DISASSOCIATED;
INIT_LIST_HEAD(&pool->worklist);
INIT_LIST_HEAD(&pool->idle_list);
@ -3832,12 +3836,12 @@ static int __init init_workqueues(void)
struct global_cwq *gcwq = get_gcwq(cpu);
struct worker_pool *pool;
if (cpu != WORK_CPU_UNBOUND)
gcwq->flags &= ~GCWQ_DISASSOCIATED;
for_each_worker_pool(pool, gcwq) {
struct worker *worker;
if (cpu != WORK_CPU_UNBOUND)
pool->flags &= ~POOL_DISASSOCIATED;
worker = create_worker(pool);
BUG_ON(!worker);
spin_lock_irq(&gcwq->lock);