linux-kernel - Re: [PATCH v3 6/6] freezer,sched: Rewrite core freezer logic

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Date:   Mon, 26 Sep 2022 20:22:18 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Christian Borntraeger <borntraeger@...ux.ibm.com>
Cc:     bigeasy@...utronix.de, dietmar.eggemann@....com,
        ebiederm@...ssion.com, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, mgorman@...e.de, mingo@...nel.org,
        oleg@...hat.com, rjw@...ysocki.net, rostedt@...dmis.org,
        tj@...nel.org, vincent.guittot@...aro.org, will@...nel.org,
        Marc Hartmayer <mhartmay@...ux.ibm.com>,
        Amit Shah <amit@...nel.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>
Subject: Re: [PATCH v3 6/6] freezer,sched: Rewrite core freezer logic

On Mon, Sep 26, 2022 at 08:06:46PM +0200, Peter Zijlstra wrote:

> Let me go git-grep some to see if there's more similar fail.

I've ended up with the below...

---
 include/linux/wait.h | 2 +-
 kernel/hung_task.c   | 8 ++++++--
 kernel/sched/core.c  | 2 +-
 3 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/include/linux/wait.h b/include/linux/wait.h
index 14ad8a0e9fac..7f5a51aae0a7 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -281,7 +281,7 @@ static inline void wake_up_pollfree(struct wait_queue_head *wq_head)
 
 #define ___wait_is_interruptible(state)						\
 	(!__builtin_constant_p(state) ||					\
-		state == TASK_INTERRUPTIBLE || state == TASK_KILLABLE)		\
+	 (state & (TASK_INTERRUPTIBLE | TASK_WAKEKILL)))
 
 extern void init_wait_entry(struct wait_queue_entry *wq_entry, int flags);
 
diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index f1321c03c32a..4a8a713fd67b 100644
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -191,6 +191,8 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
 	hung_task_show_lock = false;
 	rcu_read_lock();
 	for_each_process_thread(g, t) {
+		unsigned int state;
+
 		if (!max_count--)
 			goto unlock;
 		if (time_after(jiffies, last_break + HUNG_TASK_LOCK_BREAK)) {
@@ -198,8 +200,10 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
 				goto unlock;
 			last_break = jiffies;
 		}
-		/* use "==" to skip the TASK_KILLABLE tasks waiting on NFS */
-		if (READ_ONCE(t->__state) == TASK_UNINTERRUPTIBLE)
+		/* skip the TASK_KILLABLE tasks -- these can be killed */
+		state == READ_ONCE(t->__state);
+		if ((state & TASK_UNINTERRUPTIBLE) &&
+		    !(state & TASK_WAKEKILL))
 			check_hung_task(t, timeout);
 	}
  unlock:
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 1095917ed048..12ee5b98e2c4 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8885,7 +8885,7 @@ state_filter_match(unsigned long state_filter, struct task_struct *p)
 	 * When looking for TASK_UNINTERRUPTIBLE skip TASK_IDLE (allows
 	 * TASK_KILLABLE).
 	 */
-	if (state_filter == TASK_UNINTERRUPTIBLE && state == TASK_IDLE)
+	if (state_filter == TASK_UNINTERRUPTIBLE && state & TASK_NOLOAD)
 		return false;
 
 	return true;