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Message-Id: <20180517043448.3152269-3-tj@kernel.org>
Date: Wed, 16 May 2018 21:34:44 -0700
From: Tejun Heo <tj@...nel.org>
To: torvalds@...ux-foundation.org, jiangshanlai@...il.com,
akpm@...ux-foundation.org
Cc: linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
kernel-team@...com, csmall@....com.au, Tejun Heo <tj@...nel.org>
Subject: [PATCH 2/6] workqueue: Replace pool->attach_mutex with global wq_pool_attach_mutex
To improve workqueue visibility, we want to be able to access
workqueue information from worker tasks. The per-pool attach mutex
makes that difficult because there's no way of stabilizing task ->
worker pool association without knowing the pool first.
Worker attach/detach is a slow path and there's no need for different
pools to be able to perform them concurrently. This patch replaces
the per-pool attach_mutex with global wq_pool_attach_mutex to prepare
for visibility improvement changes.
Signed-off-by: Tejun Heo <tj@...nel.org>
---
kernel/workqueue.c | 41 ++++++++++++++++++++---------------------
1 file changed, 20 insertions(+), 21 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index ca7959b..91fe0a6 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -66,7 +66,7 @@ enum {
* be executing on any CPU. The pool behaves as an unbound one.
*
* Note that DISASSOCIATED should be flipped only while holding
- * attach_mutex to avoid changing binding state while
+ * wq_pool_attach_mutex to avoid changing binding state while
* worker_attach_to_pool() is in progress.
*/
POOL_MANAGER_ACTIVE = 1 << 0, /* being managed */
@@ -123,7 +123,7 @@ enum {
* cpu or grabbing pool->lock is enough for read access. If
* POOL_DISASSOCIATED is set, it's identical to L.
*
- * A: pool->attach_mutex protected.
+ * A: wq_pool_attach_mutex protected.
*
* PL: wq_pool_mutex protected.
*
@@ -166,7 +166,6 @@ struct worker_pool {
/* L: hash of busy workers */
struct worker *manager; /* L: purely informational */
- struct mutex attach_mutex; /* attach/detach exclusion */
struct list_head workers; /* A: attached workers */
struct completion *detach_completion; /* all workers detached */
@@ -297,6 +296,7 @@ static bool wq_numa_enabled; /* unbound NUMA affinity enabled */
static struct workqueue_attrs *wq_update_unbound_numa_attrs_buf;
static DEFINE_MUTEX(wq_pool_mutex); /* protects pools and workqueues list */
+static DEFINE_MUTEX(wq_pool_attach_mutex); /* protects worker attach/detach */
static DEFINE_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */
static DECLARE_WAIT_QUEUE_HEAD(wq_manager_wait); /* wait for manager to go away */
@@ -399,14 +399,14 @@ static void workqueue_sysfs_unregister(struct workqueue_struct *wq);
* @worker: iteration cursor
* @pool: worker_pool to iterate workers of
*
- * This must be called with @pool->attach_mutex.
+ * This must be called with wq_pool_attach_mutex.
*
* The if/else clause exists only for the lockdep assertion and can be
* ignored.
*/
#define for_each_pool_worker(worker, pool) \
list_for_each_entry((worker), &(pool)->workers, node) \
- if (({ lockdep_assert_held(&pool->attach_mutex); false; })) { } \
+ if (({ lockdep_assert_held(&wq_pool_attach_mutex); false; })) { } \
else
/**
@@ -1724,7 +1724,7 @@ static struct worker *alloc_worker(int node)
static void worker_attach_to_pool(struct worker *worker,
struct worker_pool *pool)
{
- mutex_lock(&pool->attach_mutex);
+ mutex_lock(&wq_pool_attach_mutex);
/*
* set_cpus_allowed_ptr() will fail if the cpumask doesn't have any
@@ -1733,16 +1733,16 @@ static void worker_attach_to_pool(struct worker *worker,
set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask);
/*
- * The pool->attach_mutex ensures %POOL_DISASSOCIATED remains
- * stable across this function. See the comments above the
- * flag definition for details.
+ * The wq_pool_attach_mutex ensures %POOL_DISASSOCIATED remains
+ * stable across this function. See the comments above the flag
+ * definition for details.
*/
if (pool->flags & POOL_DISASSOCIATED)
worker->flags |= WORKER_UNBOUND;
list_add_tail(&worker->node, &pool->workers);
- mutex_unlock(&pool->attach_mutex);
+ mutex_unlock(&wq_pool_attach_mutex);
}
/**
@@ -1759,11 +1759,11 @@ static void worker_detach_from_pool(struct worker *worker,
{
struct completion *detach_completion = NULL;
- mutex_lock(&pool->attach_mutex);
+ mutex_lock(&wq_pool_attach_mutex);
list_del(&worker->node);
if (list_empty(&pool->workers))
detach_completion = pool->detach_completion;
- mutex_unlock(&pool->attach_mutex);
+ mutex_unlock(&wq_pool_attach_mutex);
/* clear leftover flags without pool->lock after it is detached */
worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND);
@@ -3271,7 +3271,6 @@ static int init_worker_pool(struct worker_pool *pool)
timer_setup(&pool->mayday_timer, pool_mayday_timeout, 0);
- mutex_init(&pool->attach_mutex);
INIT_LIST_HEAD(&pool->workers);
ida_init(&pool->worker_ida);
@@ -3354,10 +3353,10 @@ static void put_unbound_pool(struct worker_pool *pool)
WARN_ON(pool->nr_workers || pool->nr_idle);
spin_unlock_irq(&pool->lock);
- mutex_lock(&pool->attach_mutex);
+ mutex_lock(&wq_pool_attach_mutex);
if (!list_empty(&pool->workers))
pool->detach_completion = &detach_completion;
- mutex_unlock(&pool->attach_mutex);
+ mutex_unlock(&wq_pool_attach_mutex);
if (pool->detach_completion)
wait_for_completion(pool->detach_completion);
@@ -4600,7 +4599,7 @@ static void unbind_workers(int cpu)
struct worker *worker;
for_each_cpu_worker_pool(pool, cpu) {
- mutex_lock(&pool->attach_mutex);
+ mutex_lock(&wq_pool_attach_mutex);
spin_lock_irq(&pool->lock);
/*
@@ -4616,7 +4615,7 @@ static void unbind_workers(int cpu)
pool->flags |= POOL_DISASSOCIATED;
spin_unlock_irq(&pool->lock);
- mutex_unlock(&pool->attach_mutex);
+ mutex_unlock(&wq_pool_attach_mutex);
/*
* Call schedule() so that we cross rq->lock and thus can
@@ -4657,7 +4656,7 @@ static void rebind_workers(struct worker_pool *pool)
{
struct worker *worker;
- lockdep_assert_held(&pool->attach_mutex);
+ lockdep_assert_held(&wq_pool_attach_mutex);
/*
* Restore CPU affinity of all workers. As all idle workers should
@@ -4727,7 +4726,7 @@ static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu)
static cpumask_t cpumask;
struct worker *worker;
- lockdep_assert_held(&pool->attach_mutex);
+ lockdep_assert_held(&wq_pool_attach_mutex);
/* is @cpu allowed for @pool? */
if (!cpumask_test_cpu(cpu, pool->attrs->cpumask))
@@ -4762,14 +4761,14 @@ int workqueue_online_cpu(unsigned int cpu)
mutex_lock(&wq_pool_mutex);
for_each_pool(pool, pi) {
- mutex_lock(&pool->attach_mutex);
+ mutex_lock(&wq_pool_attach_mutex);
if (pool->cpu == cpu)
rebind_workers(pool);
else if (pool->cpu < 0)
restore_unbound_workers_cpumask(pool, cpu);
- mutex_unlock(&pool->attach_mutex);
+ mutex_unlock(&wq_pool_attach_mutex);
}
/* update NUMA affinity of unbound workqueues */
--
2.9.5
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