linux-kernel - Re: [RFC PATCH 0/4] Add hazard pointers to kernel

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Message-ID: <CAHk-=wjzj+WL6uE0J7d4fuiWAygMzTpvZqZxR+yQJm84TTbBCg@mail.gmail.com>
Date: Thu, 19 Sep 2024 08:46:26 +0200
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Neeraj Upadhyay <Neeraj.Upadhyay@....com>, John Johansen <john.johansen@...onical.com>
Cc: Boqun Feng <boqun.feng@...il.com>, linux-kernel@...r.kernel.org, rcu@...r.kernel.org, 
	linux-mm@...ck.org, lkmm@...r.kernel.org, 
	"Paul E. McKenney" <paulmck@...nel.org>, Frederic Weisbecker <frederic@...nel.org>, 
	Neeraj Upadhyay <neeraj.upadhyay@...nel.org>, Joel Fernandes <joel@...lfernandes.org>, 
	Josh Triplett <josh@...htriplett.org>, Uladzislau Rezki <urezki@...il.com>, 
	Steven Rostedt <rostedt@...dmis.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, 
	Lai Jiangshan <jiangshanlai@...il.com>, Zqiang <qiang.zhang1211@...il.com>, 
	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>, 
	Waiman Long <longman@...hat.com>, Mark Rutland <mark.rutland@....com>, 
	Thomas Gleixner <tglx@...utronix.de>, Kent Overstreet <kent.overstreet@...il.com>, 
	Vlastimil Babka <vbabka@...e.cz>, maged.michael@...il.com
Subject: Re: [RFC PATCH 0/4] Add hazard pointers to kernel

On Thu, 19 Sept 2024 at 00:44, Neeraj Upadhyay <Neeraj.Upadhyay@....com> wrote:
>
> While we were working on this problem, this refcount scalability issue got
> resolved  recently with conditional ref acquisition [3] (however, there are new
> developments in apparmor code which might bring back the refcount problem [4]).

Honestly, the various security layers should be a whole lot more
careful about their horrid performance issues, and I think that [4]
you point at needs to just be headed off at the pass.

No  more "the security layer is so bad at performance that we have to
introduce new ref mechanisms", please. Let's push back on bad security
layer code instead.

                Linus