linux-kernel - Re: [PATCH v2 2/3] livepatch: send a fake signal to all blocking tasks

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Date:   Wed, 16 Aug 2017 16:37:48 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Miroslav Benes <mbenes@...e.cz>
Cc:     jpoimboe@...hat.com, jeyu@...nel.org, jikos@...nel.org,
        lpechacek@...e.cz, live-patching@...r.kernel.org,
        linux-kernel@...r.kernel.org, Oleg Nesterov <oleg@...hat.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        linuxppc-dev@...ts.ozlabs.org, x86@...nel.org
Subject: Re: [PATCH v2 2/3] livepatch: send a fake signal to all blocking
 tasks

On Thu 2017-08-10 12:48:14, Miroslav Benes wrote:
> Live patching consistency model is of LEAVE_PATCHED_SET and
> SWITCH_THREAD. This means that all tasks in the system have to be marked
> one by one as safe to call a new patched function. Safe means when a
> task is not (sleeping) in a set of patched functions. That is, no
> patched function is on the task's stack. Another clearly safe place is
> the boundary between kernel and userspace. The patching waits for all
> tasks to get outside of the patched set or to cross the boundary. The
> transition is completed afterwards.
> 
> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> index 79022b7eca2c..a359340c924d 100644
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -452,7 +452,7 @@ EXPORT_SYMBOL_GPL(klp_enable_patch);
>  static ssize_t force_show(struct kobject *kobj,
>  			  struct kobj_attribute *attr, char *buf)
>  {
> -	return sprintf(buf, "No operation is currently permitted.\n");
> +	return sprintf(buf, "signal\n");

This makes invalid the "NOTE:" above this function ;-)

Best Regards,
Petr