From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, John Crispin Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Grygorii Strashko , Thomas Gleixner , Frederic Weisbecker , Ingo Molnar , Anna-Maria Gleixner , Geert Uytterhoeven Subject: [PATCH 4.14 63/64] tick/nohz: Prevent bogus softirq pending warning Date: Thu, 27 Sep 2018 11:04:20 +0200 Message-Id: <20180927090258.473509321@linuxfoundation.org> In-Reply-To: <20180927090249.801943776@linuxfoundation.org> References: <20180927090249.801943776@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Thomas Gleixner Commit 0a0e0829f990 ("nohz: Fix missing tick reprogram when interrupting an inline softirq") got backported to stable trees and now causes the NOHZ softirq pending warning to trigger. It's not an upstream issue as the NOHZ update logic has been changed there. The problem is when a softirq disabled section gets interrupted and on return from interrupt the tick/nohz state is evaluated, which then can observe pending soft interrupts. These soft interrupts are legitimately pending because they cannot be processed as long as soft interrupts are disabled and the interrupted code will correctly process them when soft interrupts are reenabled. Add a check for softirqs disabled to the pending check to prevent the warning. Reported-by: Grygorii Strashko Reported-by: John Crispin Signed-off-by: Thomas Gleixner Tested-by: Grygorii Strashko Tested-by: John Crispin Cc: Frederic Weisbecker Cc: Ingo Molnar Cc: Anna-Maria Gleixner Cc: stable@vger.kernel.org Fixes: 2d898915ccf4838c ("nohz: Fix missing tick reprogram when interrupting an inline softirq") Acked-by: Frederic Weisbecker Tested-by: Geert Uytterhoeven --- kernel/time/tick-sched.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -908,7 +908,7 @@ static bool can_stop_idle_tick(int cpu, if (unlikely(local_softirq_pending() && cpu_online(cpu))) { static int ratelimit; - if (ratelimit < 10 && + if (ratelimit < 10 && !in_softirq() && (local_softirq_pending() & SOFTIRQ_STOP_IDLE_MASK)) { pr_warn("NOHZ: local_softirq_pending %02x\n", (unsigned int) local_softirq_pending());