Openwall GNU/*/Linux - a small security-enhanced Linux distro for servers
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Date: Mon, 30 Oct 2017 16:22:44 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: "Tobin C. Harding" <me@...in.cc>
Cc: "Jason A. Donenfeld" <Jason@...c4.com>,
 kernel-hardening@...ts.openwall.com, Theodore Ts'o <tytso@....edu>, Linus
 Torvalds <torvalds@...ux-foundation.org>, Kees Cook
 <keescook@...omium.org>, Paolo Bonzini <pbonzini@...hat.com>, Tycho
 Andersen <tycho@...ker.com>, "Roberts, William C"
 <william.c.roberts@...el.com>, Tejun Heo <tj@...nel.org>, Jordan Glover
 <Golden_Miller83@...tonmail.ch>, Greg KH <gregkh@...uxfoundation.org>, Petr
 Mladek <pmladek@...e.com>, Joe Perches <joe@...ches.com>, Ian Campbell
 <ijc@...lion.org.uk>, Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon
 <wilal.deacon@....com>, Chris Fries <cfries@...gle.com>, Dave Weinstein
 <olorin@...gle.com>, Daniel Micay <danielmicay@...il.com>, Djalal Harouni
 <tixxdz@...il.com>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7] printk: hash addresses printed with %p

On Wed, 25 Oct 2017 14:49:34 +1100
"Tobin C. Harding" <me@...in.cc> wrote:
> 
> First, the static_key stuff.
> 
> DEFINE_STATIC_KEY_TRUE(no_ptr_secret) : Doesn't sleep, just a
> declaration. 
> 
> if (static_branch_unlikely(&no_ptr_secret)) {} : Doesn't sleep, just
> some assembler to jump to returning true or false.
> 
> static_branch_disable(&no_ptr_secret) : Doesn't sleep, just atomic read
> and set and maybe a WARN_ONCE.

How quickly do you need static_branch_disable() executed? You could
always pass the work off to a worker thread (that can schedule).

random_ready_callback -> initiates worker thread -> enables the static branch

-- Steve

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