From: Thomas Gleixner <tglx@linutronix.de>
To: Frederic Weisbecker <frederic@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>, Ingo Molnar <mingo@redhat.com>,
Nicholas Piggin <npiggin@gmail.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: Fri, 24 May 2024 19:16:19 +0200 [thread overview]
Message-ID: <878qzzdtb0.ffs@tglx> (raw)
In-Reply-To: <ZlCwKk65-eL0FrKX@pavilion.home>
On Fri, May 24 2024 at 17:20, Frederic Weisbecker wrote:
> Le Fri, May 24, 2024 at 11:31:12AM +0200, Thomas Gleixner a écrit :
>> >> Race with tick_nohz_stop_tick() on boot CPU which can set
>> >> tick_do_timer_cpu = TICK_DO_TIMER_NONE? Is it really bad?
>>
>> This can't happen.
>
> Actually... The boot CPU is nohz_full and nothing prevents it
> from stopping its tick once IRQs are enabled and before calling
> tick_nohz_idle_enter(). When that happens, tick_nohz_full_update_tick()
> doesn't go through can_stop_idle_tick() and therefore doesn't check if it
> is the timekeeper. And then it goes through tick_nohz_stop_tick() which
> can set tick_do_timer_cpu = TICK_DO_TIMER_NONE.
OMG...
next prev parent reply other threads:[~2024-05-24 17:16 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 [this message]
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
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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