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Subject[PATCH 11/31] workqueue: replace get_pwq() with explicit per_cpu_ptr() accesses and first_pwq()
Date
get_pwq() takes @cpu, which can also be WORK_CPU_UNBOUND, and @wq and
returns the matching pwq (pool_workqueue). We want to move away from
using @cpu for identifying pools and pwqs for unbound pools with
custom attributes and there is only one user - workqueue_congested() -
which makes use of the WQ_UNBOUND conditional in get_pwq(). All other
users already know whether they're dealing with a per-cpu or unbound
workqueue.

Replace get_pwq() with explicit per_cpu_ptr(wq->cpu_pwqs, cpu) for
per-cpu workqueues and first_pwq() for unbound ones, and open-code
WQ_UNBOUND conditional in workqueue_congested().

Note that this makes workqueue_congested() behave sligntly differently
when @cpu other than WORK_CPU_UNBOUND is specified. It ignores @cpu
for unbound workqueues and always uses the first pwq instead of
oopsing.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
kernel/workqueue.c | 29 ++++++++++++++---------------
1 file changed, 14 insertions(+), 15 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 79840b9..02f51b8 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -463,16 +463,9 @@ static struct worker_pool *get_std_worker_pool(int cpu, bool highpri)
return &pools[highpri];
}

-static struct pool_workqueue *get_pwq(int cpu, struct workqueue_struct *wq)
+static struct pool_workqueue *first_pwq(struct workqueue_struct *wq)
{
- if (!(wq->flags & WQ_UNBOUND)) {
- if (likely(cpu < nr_cpu_ids))
- return per_cpu_ptr(wq->cpu_pwqs, cpu);
- } else if (likely(cpu == WORK_CPU_UNBOUND)) {
- return list_first_entry(&wq->pwqs, struct pool_workqueue,
- pwqs_node);
- }
- return NULL;
+ return list_first_entry(&wq->pwqs, struct pool_workqueue, pwqs_node);
}

static unsigned int work_color_to_flags(int color)
@@ -1192,7 +1185,7 @@ static void __queue_work(int cpu, struct workqueue_struct *wq,
* work needs to be queued on that cpu to guarantee
* non-reentrancy.
*/
- pwq = get_pwq(cpu, wq);
+ pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
last_pool = get_work_pool(work);

if (last_pool && last_pool != pwq->pool) {
@@ -1203,7 +1196,7 @@ static void __queue_work(int cpu, struct workqueue_struct *wq,
worker = find_worker_executing_work(last_pool, work);

if (worker && worker->current_pwq->wq == wq) {
- pwq = get_pwq(last_pool->cpu, wq);
+ pwq = per_cpu_ptr(wq->cpu_pwqs, last_pool->cpu);
} else {
/* meh... not running there, queue here */
spin_unlock(&last_pool->lock);
@@ -1213,7 +1206,7 @@ static void __queue_work(int cpu, struct workqueue_struct *wq,
spin_lock(&pwq->pool->lock);
}
} else {
- pwq = get_pwq(WORK_CPU_UNBOUND, wq);
+ pwq = first_pwq(wq);
spin_lock(&pwq->pool->lock);
}

@@ -1652,7 +1645,7 @@ static void rebind_workers(struct worker_pool *pool)
else
wq = system_wq;

- insert_work(get_pwq(pool->cpu, wq), rebind_work,
+ insert_work(per_cpu_ptr(wq->cpu_pwqs, pool->cpu), rebind_work,
worker->scheduled.next,
work_color_to_flags(WORK_NO_COLOR));
}
@@ -3090,7 +3083,8 @@ static int alloc_and_link_pwqs(struct workqueue_struct *wq)
return -ENOMEM;

for_each_possible_cpu(cpu) {
- struct pool_workqueue *pwq = get_pwq(cpu, wq);
+ struct pool_workqueue *pwq =
+ per_cpu_ptr(wq->cpu_pwqs, cpu);

pwq->pool = get_std_worker_pool(cpu, highpri);
list_add_tail(&pwq->pwqs_node, &wq->pwqs);
@@ -3345,7 +3339,12 @@ EXPORT_SYMBOL_GPL(workqueue_set_max_active);
*/
bool workqueue_congested(int cpu, struct workqueue_struct *wq)
{
- struct pool_workqueue *pwq = get_pwq(cpu, wq);
+ struct pool_workqueue *pwq;
+
+ if (!(wq->flags & WQ_UNBOUND))
+ pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
+ else
+ pwq = first_pwq(wq);

return !list_empty(&pwq->delayed_works);
}
--
1.8.1.2


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