linux-kernel - [PATCH] kthread: kthread_should_stop() checks if we're a kthread

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Date:   Mon, 20 Nov 2023 17:15:03 -0500
From:   Kent Overstreet <kent.overstreet@...ux.dev>
To:     linux-kernel@...r.kernel.org
Cc:     Kent Overstreet <kent.overstreet@...ux.dev>,
        Nicholas Piggin <npiggin@...il.com>,
        Mike Christie <michael.christie@...cle.com>,
        Zqiang <qiang1.zhang@...el.com>, Petr Mladek <pmladek@...e.com>
Subject: [PATCH] kthread: kthread_should_stop() checks if we're a kthread

bcachefs has a fair amount of code that may or may not be running from a
kthread (it may instead be called by a userspace ioctl); having
kthread_should_stop() check if we're a kthread enables a fair bit of
cleanup and makes it safer to use.

Cc: Nicholas Piggin <npiggin@...il.com>
Cc: Mike Christie <michael.christie@...cle.com>
Cc: Zqiang <qiang1.zhang@...el.com>
Cc: Petr Mladek <pmladek@...e.com>
Signed-off-by: Kent Overstreet <kent.overstreet@...ux.dev>
---
 kernel/kthread.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/kthread.c b/kernel/kthread.c
index 1eea53050bab..fe6090ddf414 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -155,7 +155,8 @@ void free_kthread_struct(struct task_struct *k)
  */
 bool kthread_should_stop(void)
 {
-	return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags);
+	return (current->flags & PF_KTHREAD) &&
+		test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags);
 }
 EXPORT_SYMBOL(kthread_should_stop);
 
-- 
2.42.0