linux-kernel - [PATCH v2] x86/entry: Use should_resched() in idtentry_exit_cond

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Date:   Wed, 1 Jul 2020 10:35:53 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H . Peter Anvin " <hpa@...or.com>
Subject: [PATCH v2] x86/entry: Use should_resched() in
 idtentry_exit_cond_resched()

The TIF_NEED_RESCHED bit is inlined on x86 into the preemption counter.
By using should_resched(0) instead of need_resched() the same check can
be performed which uses the same variable as 'preempt_count()` which was
issued before.

Use should_resched(0) instead need_resched().

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
v1…v2: Use should_resched() but keep the !preempt_count() check.

 arch/x86/entry/common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index bd3f14175193c..0bb6966f62738 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -615,11 +615,11 @@ static void idtentry_exit_cond_resched(struct pt_regs *regs, bool may_sched)
 	if (may_sched && !preempt_count()) {
 		/* Sanity check RCU and thread stack */
 		rcu_irq_exit_check_preempt();
 		if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
 			WARN_ON_ONCE(!on_thread_stack());
-		if (need_resched())
+		if (should_resched(0))
 			preempt_schedule_irq();
 	}
 	/* Covers both tracing and lockdep */
 	trace_hardirqs_on();
 }
-- 
2.27.0