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From: Thomas Gleixner <tglx@linutronix.de>
To: Nicholas Piggin <npiggin@gmail.com>, Oleg Nesterov <oleg@redhat.com>
Cc: Frederic Weisbecker <frederic@kernel.org>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Phil Auld <pauld@redhat.com>,
	Chris von Recklinghausen <crecklin@redhat.com>,
	linux-kernel@vger.kernel.org
Subject: Re: sched/isolation: tick_take_do_timer_from_boot() calls smp_call_function_single() with irqs disabled
Date: Mon, 27 May 2024 18:13:01 +0200	[thread overview]
Message-ID: <87plt7b5de.ffs@tglx> (raw)
In-Reply-To: <D1KDJILBPEKS.27MVR6A44NMX8@gmail.com>

On Mon, May 27 2024 at 21:01, Nicholas Piggin wrote:
> On Mon May 27, 2024 at 5:27 AM AEST, Oleg Nesterov wrote:
>> The more I grep the more I confused.
>>
>> On 05/25, Thomas Gleixner wrote:
>> >
>> > Right. It does not happen because the kernel starts with jiffies as
>> > clocksource except on S390. The jiffies clocksource is not qualified to
>> > switch over to NOHZ mode for obvious reasons.
>>
>> Not obvious for those who never looked at this code ;)
>>
>> OK, clocksource_jiffies doesn't have CLOCK_SOURCE_VALID_FOR_HRES,
>
> jiffies clocksource requires a timer to run it I suppose.

Yes, but it's all periodic (nohz disabled) mode until
clocksource_done_booting() selects a high resolution clocksource and
kicks the NOHZ stuff alive. That's a fs_initcall() and happens late in
the boot process.

Thanks,

        tglx

  parent reply	other threads:[~2024-05-27 16:13 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-05-22 15:17 sched/isolation: tick_take_do_timer_from_boot() calls smp_call_function_single() with irqs disabled Oleg Nesterov
2024-05-23 13:23 ` Oleg Nesterov
2024-05-24  9:31   ` Thomas Gleixner
2024-05-24 14:10     ` Oleg Nesterov
2024-05-24 15:22       ` Frederic Weisbecker
2024-05-24 15:20     ` Frederic Weisbecker
2024-05-24 17:16       ` Thomas Gleixner
2024-05-24 18:37       ` Oleg Nesterov
2024-05-24 22:06         ` Thomas Gleixner
2024-05-25 13:51           ` Oleg Nesterov
2024-05-25 14:13             ` Oleg Nesterov
2024-05-26 19:27           ` Oleg Nesterov
2024-05-26 20:52             ` Frederic Weisbecker
2024-05-27 15:57               ` Oleg Nesterov
2024-05-27 11:01             ` Nicholas Piggin
2024-05-27 15:57               ` Oleg Nesterov
2024-05-28  1:02                 ` Nicholas Piggin
2024-05-28 12:19                   ` Oleg Nesterov
2024-05-27 16:13               ` Thomas Gleixner [this message]
2024-05-26 20:57           ` Frederic Weisbecker
2024-05-27  9:10           ` Nicholas Piggin
2024-05-27 10:23             ` Thomas Gleixner
2024-05-27 11:16               ` Nicholas Piggin
2024-05-28 12:20 ` [PATCH] tick/nohz_full: don't abuse smp_call_function_single() in tick_setup_device() Oleg Nesterov
2024-05-28 12:22   ` Oleg Nesterov
2024-05-30 12:40   ` [PATCH] tick/nohz_full: turn tick_do_timer_boot_cpu into boot_cpu_is_nohz_full Oleg Nesterov
2024-06-03 15:35     ` [PATCH v2] " Oleg Nesterov
2024-06-03 21:44       ` Frederic Weisbecker
2024-06-04  5:08       ` Nicholas Piggin
2024-05-30 14:52   ` [PATCH] tick/nohz_full: don't abuse smp_call_function_single() in tick_setup_device() Frederic Weisbecker
2024-05-30 16:52     ` Oleg Nesterov
2024-05-30 17:01     ` Oleg Nesterov
2024-06-01 14:03     ` Oleg Nesterov
2024-06-02 21:29       ` Frederic Weisbecker
2024-06-03 15:41         ` Oleg Nesterov
2024-06-03 21:45           ` Frederic Weisbecker
2024-06-10 15:55   ` [PING ;)] " Oleg Nesterov
2024-06-10 18:15     ` Thomas Gleixner
2024-06-10 18:26   ` [tip: timers/urgent] tick/nohz_full: Don't " tip-bot2 for Oleg Nesterov
2024-06-10 19:42     ` Frederic Weisbecker

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