From: Greg KH <gregkh@linuxfoundation.org>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Mathias Krause <minipli@grsecurity.net>,
Luiz Capitulino <luizcap@amazon.com>,
Sven-Haegar Koch <haegar@sdinet.de>,
"Bhatnagar, Rishabh" <risbhat@amazon.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"sashal@kernel.org" <sashal@kernel.org>,
abuehaze@amazon.com,
"stable@vger.kernel.org" <stable@vger.kernel.org>,
Frederic Weisbecker <frederic@kernel.org>,
Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH] tick/common: Align tick period during sched_timer setup.
Date: Mon, 19 Jun 2023 08:18:10 +0200 [thread overview]
Message-ID: <2023061944-uprising-applaud-990a@gregkh> (raw)
In-Reply-To: <20230615091830.RxMV2xf_@linutronix.de>
On Thu, Jun 15, 2023 at 11:18:30AM +0200, Sebastian Andrzej Siewior wrote:
> From: Thomas Gleixner <tglx@linutronix.de>
>
> The tick period is aligned very early while the first clock_event_device
> is registered. The system runs in periodic mode and switches later to
> one-shot mode if possible.
>
> The next wake-up event is programmed based on aligned value
> (tick_next_period) but the delta value, that is used to program the
> clock_event_device, is computed based on ktime_get().
>
> With the subtracted offset, the devices fires in less than the exacted
> time frame. With a large enough offset the system programs the timer for
> the next wake-up and the remaining time left is too little to make any
> boot progress. The system hangs.
>
> Move the alignment later to the setup of tick_sched timer. At this point
> the system switches to oneshot mode and a highres clocksource is
> available. It safe to update tick_next_period ktime_get() will now
> return accurate (not jiffies based) time.
>
> [bigeasy: Patch description + testing].
>
> Reported-by: Mathias Krause <minipli@grsecurity.net>
> Reported-by: "Bhatnagar, Rishabh" <risbhat@amazon.com>
> Fixes: e9523a0d81899 ("tick/common: Align tick period with the HZ tick.")
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> Link: https://lore.kernel.org/5a56290d-806e-b9a5-f37c-f21958b5a8c0@grsecurity.net
> Link: https://lore.kernel.org/12c6f9a3-d087-b824-0d05-0d18c9bc1bf3@amazon.com
> ---
> kernel/time/tick-common.c | 11 +----------
> kernel/time/tick-sched.c | 13 ++++++++++++-
> 2 files changed, 13 insertions(+), 11 deletions(-)
What's the status of this fix, I didn't see it in -rc7, am I looking in
the wrong place?
thanks,
greg k-h
next prev parent reply other threads:[~2023-06-19 6:18 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-13 18:49 Observing RCU stalls in kernel 5.4/5.10/5.15/6.1 stable trees Bhatnagar, Rishabh
2023-06-13 18:58 ` Bhatnagar, Rishabh
2023-06-14 9:14 ` gregkh
2023-06-14 13:08 ` Luiz Capitulino
2023-06-14 9:14 ` gregkh
2023-06-14 9:20 ` Sebastian Andrzej Siewior
2023-06-14 13:10 ` Luiz Capitulino
2023-06-14 13:45 ` Sven-Haegar Koch
2023-06-14 13:57 ` Luiz Capitulino
2023-06-14 14:30 ` Mathias Krause
2023-06-15 9:18 ` [PATCH] tick/common: Align tick period during sched_timer setup Sebastian Andrzej Siewior
2023-06-15 11:13 ` Mathias Krause
2023-06-15 12:20 ` Richard W.M. Jones
2023-06-15 14:15 ` Luiz Capitulino
2023-06-15 16:00 ` SeongJae Park
2023-06-19 6:18 ` Greg KH [this message]
2023-06-19 7:03 ` Mathias Krause
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