linux-kernel - Re: [PATCH v7] printk: hash addresses printed with %p

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Message-ID: <20171030162244.4f55e623@gandalf.local.home>
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