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From: "Chang, Junxiao" <junxiao.chang@intel.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-rt-users@vger.kernel.org" <linux-rt-users@vger.kernel.org>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"rostedt@goodmis.org" <rostedt@goodmis.org>,
	"Peh, Hock Zhang" <hock.zhang.peh@intel.com>
Subject: RE: [PATCH] softirq: wake up ktimer thread in softirq context
Date: Mon, 20 Feb 2023 08:55:09 +0000	[thread overview]
Message-ID: <BN9PR11MB5370CFD46CA0A2E245AFBE04ECA49@BN9PR11MB5370.namprd11.prod.outlook.com> (raw)
In-Reply-To: <Y++5ry75hEI2NWrK@linutronix.de>

Thank you for handling this, modified patch looks good to me.

Regards,
Junxiao

-----Original Message-----
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> 
Sent: Saturday, February 18, 2023 1:30 AM
To: Chang, Junxiao <junxiao.chang@intel.com>
Cc: linux-kernel@vger.kernel.org; linux-rt-users@vger.kernel.org; tglx@linutronix.de; rostedt@goodmis.org; Peh, Hock Zhang <hock.zhang.peh@intel.com>
Subject: Re: [PATCH] softirq: wake up ktimer thread in softirq context

On 2022-12-08 15:56:04 [+0800], Junxiao Chang wrote:
> Occiaionally timer interrupt might be triggered in softirq context, 
> ktimer thread should be woken up with RT kernel, or else ktimer thread 
> might stay in sleep state although timer interrupt has been triggered.
> 
> This change fixes a latency issue that timer handler is delayed for 
> more than 4ms in network related test.

Sorry for keeping you waiting. Your observation and patch is correct. I'm going to apply a slightly modified version of the patch (see below) after I reworded the commit message on Monday.

diff --git a/kernel/softirq.c b/kernel/softirq.c index ab1fe34326bab..82f3e68fbe220 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -664,13 +664,12 @@ static inline void __irq_exit_rcu(void)  #endif
 	account_hardirq_exit(current);
 	preempt_count_sub(HARDIRQ_OFFSET);
-	if (!in_interrupt()) {
-		if (local_softirq_pending())
-			invoke_softirq();
+	if (!in_interrupt() && local_softirq_pending())
+		invoke_softirq();
 
-		if (IS_ENABLED(CONFIG_PREEMPT_RT) && local_pending_timers())
-			wake_timersd();
-	}
+	if (IS_ENABLED(CONFIG_PREEMPT_RT) && local_pending_timers() &&
+	    !(in_nmi() | in_hardirq()))
+		wake_timersd();
 
 	tick_irq_exit();
 }

Sebastian

  reply	other threads:[~2023-02-20  8:55 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-12-08  7:56 [PATCH] softirq: wake up ktimer thread in softirq context Junxiao Chang
2022-12-20 10:44 ` Chang, Junxiao
2022-12-20 17:10   ` Alison Chaiken
2022-12-20 18:02   ` bigeasy
2022-12-20 19:28     ` Alison Chaiken
2023-01-23 18:04     ` Alison Chaiken
2023-02-10 15:32     ` Alison Chaiken
2023-02-10 16:33       ` bigeasy
2023-02-17 17:30 ` Sebastian Andrzej Siewior
2023-02-20  8:55   ` Chang, Junxiao [this message]
2023-02-20 10:53     ` Sebastian Andrzej Siewior

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