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Subject[PATCH] PM: sleep: Replace read_lock/unlock(tasklist_lock) with rcu_read_lock/unlock()
Date
From: Zqiang <qiang.zhang@windriver.com>

Using rcu_read_lock/unlock() instead of read_lock/unlock(tasklist_lock),
the task list can be traversed in parallel to any list additions or
removals, improve concurrency.

Signed-off-by: Zqiang <qiang.zhang@windriver.com>
---
kernel/power/process.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/kernel/power/process.c b/kernel/power/process.c
index 50cc63534486..0f8dee9ee097 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -48,7 +48,7 @@ static int try_to_freeze_tasks(bool user_only)

while (true) {
todo = 0;
- read_lock(&tasklist_lock);
+ rcu_read_lock();
for_each_process_thread(g, p) {
if (p == current || !freeze_task(p))
continue;
@@ -56,7 +56,7 @@ static int try_to_freeze_tasks(bool user_only)
if (!freezer_should_skip(p))
todo++;
}
- read_unlock(&tasklist_lock);
+ rcu_read_unlock();

if (!user_only) {
wq_busy = freeze_workqueues_busy();
@@ -97,13 +97,13 @@ static int try_to_freeze_tasks(bool user_only)
show_workqueue_state();

if (!wakeup || pm_debug_messages_on) {
- read_lock(&tasklist_lock);
+ rcu_read_lock();
for_each_process_thread(g, p) {
if (p != current && !freezer_should_skip(p)
&& freezing(p) && !frozen(p))
sched_show_task(p);
}
- read_unlock(&tasklist_lock);
+ rcu_read_unlock();
}
} else {
pr_cont("(elapsed %d.%03d seconds) ", elapsed_msecs / 1000,
@@ -206,13 +206,13 @@ void thaw_processes(void)

cpuset_wait_for_hotplug();

- read_lock(&tasklist_lock);
+ rcu_read_lock();
for_each_process_thread(g, p) {
/* No other threads should have PF_SUSPEND_TASK set */
WARN_ON((p != curr) && (p->flags & PF_SUSPEND_TASK));
__thaw_task(p);
}
- read_unlock(&tasklist_lock);
+ rcu_read_unlock();

WARN_ON(!(curr->flags & PF_SUSPEND_TASK));
curr->flags &= ~PF_SUSPEND_TASK;
@@ -233,12 +233,12 @@ void thaw_kernel_threads(void)

thaw_workqueues();

- read_lock(&tasklist_lock);
+ rcu_read_lock();
for_each_process_thread(g, p) {
if (p->flags & PF_KTHREAD)
__thaw_task(p);
}
- read_unlock(&tasklist_lock);
+ rcu_read_unlock();

schedule();
pr_cont("done.\n");
--
2.17.1
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