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From: Petr Mladek <pmladek@suse.com>
To: Miroslav Benes <mbenes@suse.cz>
Cc: rostedt@goodmis.org, jikos@kernel.org, joe.lawrence@redhat.com,
	jpoimboe@redhat.com, mingo@redhat.com,
	linux-kernel@vger.kernel.org, live-patching@vger.kernel.org
Subject: Re: [PATCH v2] ftrace: Introduce PERMANENT ftrace_ops flag
Date: Mon, 14 Oct 2019 16:26:20 +0200	[thread overview]
Message-ID: <20191014142620.dg3oiush5twd26ly@pathway.suse.cz> (raw)
In-Reply-To: <20191014105923.29607-1-mbenes@suse.cz>

On Mon 2019-10-14 12:59:23, Miroslav Benes wrote:
> Livepatch uses ftrace for redirection to new patched functions. It means
> that if ftrace is disabled, all live patched functions are disabled as
> well. Toggling global 'ftrace_enabled' sysctl thus affect it directly.
> It is not a problem per se, because only administrator can set sysctl
> values, but it still may be surprising.
> 
> Introduce PERMANENT ftrace_ops flag to amend this. If the
> FTRACE_OPS_FL_PERMANENT is set on any ftrace ops, the tracing cannot be
> disabled by disabling ftrace_enabled. Equally, a callback with the flag
> set cannot be registered if ftrace_enabled is disabled.
> 
> Signed-off-by: Miroslav Benes <mbenes@suse.cz>

Looks fine to me. I finally understand which ftrace_enabled toggle
we are talking about ;-)

Reviewed-by: Petr Mladek <pmladek@suse.com>

> ---
> - return codes. I chose EBUSY, because it seemed the least
>   inappropriate. I usually pick the wrong one, so suggestions are
>   welcome.

-EBUSY is perfectly fine in ftrace_enable_sysctl(). It is not ideal
in __register_ftrace_function(). But it still looks better than
-ENODEV there.

Best Regards,
Petr

  reply	other threads:[~2019-10-14 14:26 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-14 10:59 [PATCH v2] ftrace: Introduce PERMANENT ftrace_ops flag Miroslav Benes
2019-10-14 14:26 ` Petr Mladek [this message]
2019-10-14 15:17 ` Steven Rostedt
2019-10-15  7:45   ` Petr Mladek
2019-10-15 10:50     ` Miroslav Benes
2019-10-15 13:36       ` Steven Rostedt
2019-10-14 22:31 ` Joe Lawrence
2019-10-15 11:23   ` Miroslav Benes
2019-10-15 13:25     ` Joe Lawrence
2019-10-15 14:02       ` Miroslav Benes
2019-10-15 14:58     ` Joe Lawrence
2019-10-16  5:02 ` Kamalesh Babulal

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