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From: Greg KH <gregkh@linuxfoundation.org>
To: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>
Cc: stable@vger.kernel.org, sashal@kernel.org,
	Davidlohr Bueso <dave@stgolabs.net>,
	Davidlohr Bueso <dbueso@suse.de>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [RFC/PATCH for 4.14 and 4.19] lib/timerqueue: Rely on rbtree semantics for next timer
Date: Fri, 8 Oct 2021 11:10:53 +0200	[thread overview]
Message-ID: <YWALHdipnUQT6mBQ@kroah.com> (raw)
In-Reply-To: <20211007123243.595438-1-nobuhiro1.iwamatsu@toshiba.co.jp>

On Thu, Oct 07, 2021 at 09:32:43PM +0900, Nobuhiro Iwamatsu wrote:
> From: Davidlohr Bueso <dave@stgolabs.net>
> 
> commit 511885d7061eda3eb1faf3f57dcc936ff75863f1 upstream.
> 
> Simplify the timerqueue code by using cached rbtrees and rely on the tree
> leftmost node semantics to get the timer with earliest expiration time.
> This is a drop in conversion, and therefore semantics remain untouched.
> 
> The runtime overhead of cached rbtrees is be pretty much the same as the
> current head->next method, noting that when removing the leftmost node,
> a common operation for the timerqueue, the rb_next(leftmost) is O(1) as
> well, so the next timer will either be the right node or its parent.
> Therefore no extra pointer chasing. Finally, the size of the struct
> timerqueue_head remains the same.
> 
> Passes several hours of rcutorture.
> 
> Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Link: https://lkml.kernel.org/r/20190724152323.bojciei3muvfxalm@linux-r8p5
> Reference: CVE-2021-20317
> Signed-off-by: Nobuhiro Iwamatsu (CIP) <nobuhiro1.iwamatsu@toshiba.co.jp>
> ---

Now queued up, thanks.

greg k-h

      reply	other threads:[~2021-10-08  9:10 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-07 12:32 [RFC/PATCH for 4.14 and 4.19] lib/timerqueue: Rely on rbtree semantics for next timer Nobuhiro Iwamatsu
2021-10-08  9:10 ` Greg KH [this message]

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