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Date: Wed, 20 Mar 2013 03:28:06 +0800
From: Lai Jiangshan <laijs@...fujitsu.com>
To: Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org
Cc: Lai Jiangshan <laijs@...fujitsu.com>
Subject: [PATCH 06/21] workqueue: separate out pools locking into pools_mutex
currently wq_mutext protects:
* worker_pool_idr and unbound_pool_hash
* pool->refcnt
* workqueues list
* workqueue->flags, ->nr_drainers
* workqueue_freezing
We can see that it protects very different things.
So we need to split it and introduce a pools_mutex to protect:
* worker_pool_idr and unbound_pool_hash
* pool->refcnt
(all are pools related field.)
workqueue_freezing is special, it is protected by both of wq_mutext
pools_mutex. All are because get_unbound_pool() need to read it,
which are because POOL_FREEZING is a bad design which will be fixed later.
Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
---
kernel/workqueue.c | 66 ++++++++++++++++++++++++++++-----------------------
1 files changed, 36 insertions(+), 30 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index fb81159..cc5eb61 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -125,7 +125,9 @@ enum {
*
* WQ: wq_mutex protected.
*
- * WR: wq_mutex protected for writes. Sched-RCU protected for reads.
+ * PS: pools_mutex protected.
+ *
+ * PR: pools_mutex protected for writes. Sched-RCU protected for reads.
*
* PW: pwq_lock protected.
*
@@ -163,8 +165,8 @@ struct worker_pool {
struct idr worker_idr; /* MG: worker IDs and iteration */
struct workqueue_attrs *attrs; /* I: worker attributes */
- struct hlist_node hash_node; /* WQ: unbound_pool_hash node */
- int refcnt; /* WQ: refcnt for unbound pools */
+ struct hlist_node hash_node; /* PS: unbound_pool_hash node */
+ int refcnt; /* PS: refcnt for unbound pools */
/*
* The current concurrency level. As it's likely to be accessed
@@ -256,20 +258,21 @@ struct workqueue_struct {
static struct kmem_cache *pwq_cache;
-static DEFINE_MUTEX(wq_mutex); /* protects workqueues and pools */
+static DEFINE_MUTEX(wq_mutex); /* protects workqueues */
+static DEFINE_MUTEX(pools_mutex); /* protects pools */
static DEFINE_SPINLOCK(pwq_lock); /* protects pool_workqueues */
static DEFINE_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */
static LIST_HEAD(workqueues); /* WQ: list of all workqueues */
-static bool workqueue_freezing; /* WQ: have wqs started freezing? */
+static bool workqueue_freezing; /* WQ&PS: have wqs started freezing? */
/* the per-cpu worker pools */
static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS],
cpu_worker_pools);
-static DEFINE_IDR(worker_pool_idr); /* WR: idr of all pools */
+static DEFINE_IDR(worker_pool_idr); /* PR: idr of all pools */
-/* WQ: hash of all unbound pools keyed by pool->attrs */
+/* PS: hash of all unbound pools keyed by pool->attrs */
static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER);
/* I: attributes used when instantiating standard unbound pools on demand */
@@ -293,10 +296,10 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to,
#define CREATE_TRACE_POINTS
#include <trace/events/workqueue.h>
-#define assert_rcu_or_wq_mutex() \
+#define assert_rcu_or_pools_mutex() \
rcu_lockdep_assert(rcu_read_lock_sched_held() || \
- lockdep_is_held(&wq_mutex), \
- "sched RCU or wq_mutex should be held")
+ lockdep_is_held(&pools_mutex), \
+ "sched RCU or pools_mutex should be held")
#define assert_rcu_or_pwq_lock() \
rcu_lockdep_assert(rcu_read_lock_sched_held() || \
@@ -322,7 +325,7 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to,
* @pool: iteration cursor
* @pi: integer used for iteration
*
- * This must be called either with wq_mutex held or sched RCU read locked.
+ * This must be called either with pools_mutex held or sched RCU read locked.
* If the pool needs to be used beyond the locking in effect, the caller is
* responsible for guaranteeing that the pool stays online.
*
@@ -331,7 +334,7 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to,
*/
#define for_each_pool(pool, pi) \
idr_for_each_entry(&worker_pool_idr, pool, pi) \
- if (({ assert_rcu_or_wq_mutex(); false; })) { } \
+ if (({ assert_rcu_or_pools_mutex(); false; })) { } \
else
/**
@@ -488,7 +491,7 @@ static int worker_pool_assign_id(struct worker_pool *pool)
{
int ret;
- lockdep_assert_held(&wq_mutex);
+ lockdep_assert_held(&pools_mutex);
do {
if (!idr_pre_get(&worker_pool_idr, GFP_KERNEL))
@@ -606,9 +609,9 @@ static struct pool_workqueue *get_work_pwq(struct work_struct *work)
*
* Return the worker_pool @work was last associated with. %NULL if none.
*
- * Pools are created and destroyed under wq_mutex, and allows read access
+ * Pools are created and destroyed under pools_mutex, and allows read access
* under sched-RCU read lock. As such, this function should be called
- * under wq_mutex or with preemption disabled.
+ * under pools_mutex or with preemption disabled.
*
* All fields of the returned pool are accessible as long as the above
* mentioned locking is in effect. If the returned pool needs to be used
@@ -620,7 +623,7 @@ static struct worker_pool *get_work_pool(struct work_struct *work)
unsigned long data = atomic_long_read(&work->data);
int pool_id;
- assert_rcu_or_wq_mutex();
+ assert_rcu_or_pools_mutex();
if (data & WORK_STRUCT_PWQ)
return ((struct pool_workqueue *)
@@ -3428,16 +3431,16 @@ static void put_unbound_pool(struct worker_pool *pool)
{
struct worker *worker;
- mutex_lock(&wq_mutex);
+ mutex_lock(&pools_mutex);
if (--pool->refcnt) {
- mutex_unlock(&wq_mutex);
+ mutex_unlock(&pools_mutex);
return;
}
/* sanity checks */
if (WARN_ON(!(pool->flags & POOL_DISASSOCIATED)) ||
WARN_ON(!list_empty(&pool->worklist))) {
- mutex_unlock(&wq_mutex);
+ mutex_unlock(&pools_mutex);
return;
}
@@ -3446,7 +3449,7 @@ static void put_unbound_pool(struct worker_pool *pool)
idr_remove(&worker_pool_idr, pool->id);
hash_del(&pool->hash_node);
- mutex_unlock(&wq_mutex);
+ mutex_unlock(&pools_mutex);
/*
* Become the manager and destroy all workers. Grabbing
@@ -3488,7 +3491,7 @@ static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
u32 hash = wqattrs_hash(attrs);
struct worker_pool *pool;
- mutex_lock(&wq_mutex);
+ mutex_lock(&pools_mutex);
/* do we already have a matching pool? */
hash_for_each_possible(unbound_pool_hash, pool, hash_node, hash) {
@@ -3519,10 +3522,10 @@ static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs)
/* install */
hash_add(unbound_pool_hash, &pool->hash_node, hash);
out_unlock:
- mutex_unlock(&wq_mutex);
+ mutex_unlock(&pools_mutex);
return pool;
fail:
- mutex_unlock(&wq_mutex);
+ mutex_unlock(&pools_mutex);
if (pool)
put_unbound_pool(pool);
return NULL;
@@ -4199,7 +4202,7 @@ static int __cpuinit workqueue_cpu_up_callback(struct notifier_block *nfb,
case CPU_DOWN_FAILED:
case CPU_ONLINE:
- mutex_lock(&wq_mutex);
+ mutex_lock(&pools_mutex);
for_each_pool(pool, pi) {
mutex_lock(&pool->manager_mutex);
@@ -4217,7 +4220,7 @@ static int __cpuinit workqueue_cpu_up_callback(struct notifier_block *nfb,
mutex_unlock(&pool->manager_mutex);
}
- mutex_unlock(&wq_mutex);
+ mutex_unlock(&pools_mutex);
break;
}
return NOTIFY_OK;
@@ -4304,16 +4307,18 @@ void freeze_workqueues_begin(void)
mutex_lock(&wq_mutex);
+ /* set FREEZING */
+ mutex_lock(&pools_mutex);
WARN_ON_ONCE(workqueue_freezing);
workqueue_freezing = true;
- /* set FREEZING */
for_each_pool(pool, pi) {
spin_lock_irq(&pool->lock);
WARN_ON_ONCE(pool->flags & POOL_FREEZING);
pool->flags |= POOL_FREEZING;
spin_unlock_irq(&pool->lock);
}
+ mutex_unlock(&pools_mutex);
/* suppress further executions by setting max_active to zero */
spin_lock_irq(&pwq_lock);
@@ -4394,12 +4399,15 @@ void thaw_workqueues(void)
goto out_unlock;
/* clear FREEZING */
+ mutex_lock(&pools_mutex);
+ workqueue_freezing = false;
for_each_pool(pool, pi) {
spin_lock_irq(&pool->lock);
WARN_ON_ONCE(!(pool->flags & POOL_FREEZING));
pool->flags &= ~POOL_FREEZING;
spin_unlock_irq(&pool->lock);
}
+ mutex_unlock(&pools_mutex);
/* restore max_active and repopulate worklist */
spin_lock_irq(&pwq_lock);
@@ -4408,8 +4416,6 @@ void thaw_workqueues(void)
pwq_adjust_max_active(pwq);
}
spin_unlock_irq(&pwq_lock);
-
- workqueue_freezing = false;
out_unlock:
mutex_unlock(&wq_mutex);
}
@@ -4443,9 +4449,9 @@ static int __init init_workqueues(void)
pool->attrs->nice = std_nice[i++];
/* alloc pool ID */
- mutex_lock(&wq_mutex);
+ mutex_lock(&pools_mutex);
BUG_ON(worker_pool_assign_id(pool));
- mutex_unlock(&wq_mutex);
+ mutex_unlock(&pools_mutex);
}
}
--
1.7.7.6
--
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