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Message-Id: <20220804084135.92425-4-jiangshanlai@gmail.com>
Date: Thu, 4 Aug 2022 16:41:30 +0800
From: Lai Jiangshan <jiangshanlai@...il.com>
To: linux-kernel@...r.kernel.org
Cc: Lai Jiangshan <jiangshan.ljs@...group.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Tejun Heo <tj@...nel.org>, Petr Mladek <pmladek@...e.com>,
Michal Hocko <mhocko@...e.com>,
Peter Zijlstra <peterz@...radead.org>,
Wedson Almeida Filho <wedsonaf@...gle.com>,
Lai Jiangshan <jiangshanlai@...il.com>
Subject: [RFC PATCH 3/8] workqueue: Set PF_NO_SETAFFINITY instead of kthread_bind_mask()
From: Lai Jiangshan <jiangshan.ljs@...group.com>
kthread_bind_mask() can't work correctly if spurious wakeup
happens before kthread_bind_mask().
And a spuriously wakeup worker's cpumask can be possibly changed
by a userspace if worker_attach_to_pool() is called earlier than
kthread_bind_mask().
To avoid the problem caused by spurious wokeup, set PF_NO_SETAFFINITY
at the starting of workers where kthread_bind_mask() can't be used
and luckily workqueue code binds cpumask by itself, all it needs is
only PF_NO_SETAFFINITY.
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>
Cc: Tejun Heo <tj@...nel.org>,
Cc: Petr Mladek <pmladek@...e.com>
Cc: Michal Hocko <mhocko@...e.com>,
Cc: Peter Zijlstra <peterz@...radead.org>,
Cc: Wedson Almeida Filho <wedsonaf@...gle.com>
Signed-off-by: Lai Jiangshan <jiangshan.ljs@...group.com>
---
kernel/workqueue.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index f5b12c6778cc..82937c0fb21f 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1958,7 +1958,6 @@ static struct worker *create_worker(struct worker_pool *pool)
goto fail;
set_user_nice(worker->task, pool->attrs->nice);
- kthread_bind_mask(worker->task, pool->attrs->cpumask);
/* start the newly created worker */
wake_up_process(worker->task);
@@ -2380,6 +2379,8 @@ static int worker_thread(void *__worker)
struct worker *worker = __worker;
struct worker_pool *pool = worker->pool;
+ current->flags |= PF_NO_SETAFFINITY;
+
/* attach the worker to the pool */
worker_attach_to_pool(worker, pool);
@@ -2494,6 +2495,7 @@ static int rescuer_thread(void *__rescuer)
struct list_head *scheduled = &rescuer->scheduled;
bool should_stop;
+ current->flags |= PF_NO_SETAFFINITY;
set_user_nice(current, RESCUER_NICE_LEVEL);
/*
@@ -4279,7 +4281,6 @@ static int init_rescuer(struct workqueue_struct *wq)
}
wq->rescuer = rescuer;
- kthread_bind_mask(rescuer->task, cpu_possible_mask);
wake_up_process(rescuer->task);
return 0;
--
2.19.1.6.gb485710b
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