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From: Frederic Weisbecker <frederic@kernel.org>
To: Grygorii Strashko <grygorii.strashko@ti.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Greg KH <gregkh@linuxfoundation.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Anna-Maria Gleixner <anna-maria@linutronix.de>,
	stable@vger.kernel.org, Tero Kristo <t-kristo@ti.com>
Subject: Re: [PATCH] nohz: Fix missing tick reprog while interrupting inline timer softirq
Date: Fri, 24 Aug 2018 20:41:04 +0200	[thread overview]
Message-ID: <20180824184103.GD2730@lerouge> (raw)
In-Reply-To: <0d63c2bb-f75d-3f79-c19d-bb4ac9a00cd5@ti.com>

On Fri, Aug 24, 2018 at 11:10:44AM -0500, Grygorii Strashko wrote:
> Yes. i do not see local_softirq_pending messages any more
> 
> But one question, just to clarify, after patch "nohz: Fix missing tick reprog while interrupting inline timer softirq"
> the tick_nohz_irq_exit() will be called few times in case of nested interrupts (min 2):
> gic_handle_irq
>  |- irq_exit
>     |- preempt_count_sub(HARDIRQ_OFFSET); 
>     |-__do_softirq 
> 	<irqs enabled>
> 	|- gic_handle_irq()
> 	   |- irq_exit()
> 		|- tick_irq_exit()
> 		   if (!in_irq())
> 			tick_nohz_irq_exit(); <-- [1]
>     |- tick_irq_exit()
> 	if (!in_irq())
> 		tick_nohz_irq_exit(); <-- [2]
> 
> Is it correct? in 4.14 tick_nohz_irq_exit() is much more complex then in LKML now,
> and this is hot path.

That's correct and it's indeed more costly in 4.14 as then the tick is going to be programmed
twice.

  reply	other threads:[~2018-08-24 18:41 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-31 22:52 [PATCH] nohz: Fix missing tick reprog while interrupting inline timer softirq Frederic Weisbecker
2018-08-01 12:03 ` Anna-Maria Gleixner
2018-08-01 17:46 ` Thomas Gleixner
2018-08-01 21:08   ` Frederic Weisbecker
2018-08-03 11:42     ` Thomas Gleixner
2018-08-23 22:57 ` Grygorii Strashko
2018-08-24  6:17   ` Greg KH
2018-08-24  7:01     ` Thomas Gleixner
2018-08-24 14:27       ` Frederic Weisbecker
2018-08-24 16:10       ` Grygorii Strashko
2018-08-24 18:41         ` Frederic Weisbecker [this message]
2018-08-28 17:56           ` Grygorii Strashko
2018-08-30 14:10             ` John Crispin
2018-08-30 14:29               ` Thomas Gleixner
2018-08-24 16:14     ` Grygorii Strashko

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