linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Junxiao Chang <junxiao.chang@intel.com>
Cc: linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org,
	tglx@linutronix.de, rostedt@goodmis.org,
	hock.zhang.peh@intel.com
Subject: Re: [PATCH] softirq: wake up ktimer thread in softirq context
Date: Fri, 17 Feb 2023 18:30:23 +0100	[thread overview]
Message-ID: <Y++5ry75hEI2NWrK@linutronix.de> (raw)
In-Reply-To: <20221208075604.811710-1-junxiao.chang@intel.com>

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

  parent reply	other threads:[~2023-02-17 17:30 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 [this message]
2023-02-20  8:55   ` Chang, Junxiao
2023-02-20 10:53     ` Sebastian Andrzej Siewior

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=Y++5ry75hEI2NWrK@linutronix.de \
    --to=bigeasy@linutronix.de \
    --cc=hock.zhang.peh@intel.com \
    --cc=junxiao.chang@intel.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-rt-users@vger.kernel.org \
    --cc=rostedt@goodmis.org \
    --cc=tglx@linutronix.de \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).