linux-kernel - [PATCH RT 08/10] locking: Drop might_resched() from might_sleep_no_state

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Date:   Mon, 22 Nov 2021 15:38:55 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org,
        linux-rt-users <linux-rt-users@...r.kernel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Carsten Emde <C.Emde@...dl.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        John Kacur <jkacur@...hat.com>, Daniel Wagner <wagi@...om.org>,
        Tom Zanussi <zanussi@...nel.org>,
        "Srivatsa S. Bhat" <srivatsa@...il.mit.edu>
Subject: [PATCH RT 08/10] locking: Drop might_resched() from might_sleep_no_state_check()

5.10.78-rt56-rc2 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>

might_sleep_no_state_check() serves the same purpose as might_sleep()
except it is used before sleeping locks are acquired and therefore does
not check task_struct::state because the state is preserved.

That state is preserved in the locking slow path so we must not schedule
at the begin of the locking function because the state will be lost and
not preserved at that time.

Remove might_resched() from might_sleep_no_state_check() to avoid losing the
state before it is preserved.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 include/linux/kernel.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 2cff7554395d..6eb0ab994f4c 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -222,7 +222,7 @@ extern void __cant_migrate(const char *file, int line);
 	do { __might_sleep(__FILE__, __LINE__, 0); might_resched(); } while (0)
 
 # define might_sleep_no_state_check() \
-	do { ___might_sleep(__FILE__, __LINE__, 0); might_resched(); } while (0)
+	do { ___might_sleep(__FILE__, __LINE__, 0); } while (0)
 
 /**
  * cant_sleep - annotation for functions that cannot sleep
-- 
2.33.0