linux-kernel - Re: [PATCH v7 15/21] timer: Add get next timer interrupt functionality for remote CPUs

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Message-ID: <ZICaY9/vpEPoHE7q@lothringen>
Date:   Wed, 7 Jun 2023 16:55:31 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Anna-Maria Behnsen <anna-maria@...utronix.de>
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        John Stultz <jstultz@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Eric Dumazet <edumazet@...gle.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Arjan van de Ven <arjan@...radead.org>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Rik van Riel <riel@...riel.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sebastian Siewior <bigeasy@...utronix.de>,
        Giovanni Gherdovich <ggherdovich@...e.cz>,
        Lukasz Luba <lukasz.luba@....com>,
        "Gautham R . Shenoy" <gautham.shenoy@....com>
Subject: Re: [PATCH v7 15/21] timer: Add get next timer interrupt
 functionality for remote CPUs

On Wed, May 24, 2023 at 09:06:23AM +0200, Anna-Maria Behnsen wrote:
> +# ifdef CONFIG_SMP
> +/**
> + * fetch_next_timer_interrupt_remote
> + * @basej:	base time jiffies
> + * @basem:	base time clock monotonic
> + * @tevt:	Pointer to the storage for the expiry values
> + * @cpu:	Remote CPU
> + *
> + * Stores the next pending local and global timer expiry values in the
> + * struct pointed to by @tevt. If a queue is empty the corresponding
> + * field is set to KTIME_MAX. If local event expires before global
> + * event, global event is set to KTIME_MAX as well.
> + *
> + * Caller needs to make sure timer base locks are held (use
> + * timer_lock_remote_bases() for this purpose). Caller must make sure
> + * interrupts are reopened, if required.

That last sentence looks weird. All we want is the caller to call this
and the timer_[un]lock functions with interrupts disabled.

Now of course at some point the caller will need to unmask the IRQs
but heh, not our problem :)

Reviewed-by: Frederic Weisbecker <frederic@...nel.org>