linux-kernel - Re: [PATCH] Text Edit Lock - Architecture Independent Code

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Date:	Tue, 3 Mar 2009 01:32:37 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Masami Hiramatsu <mhiramat@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	"H. Peter Anvin" <hpa@...or.com>,
	Steven Rostedt <srostedt@...hat.com>
Subject: Re: [PATCH] Text Edit Lock - Architecture Independent Code


* Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca> wrote:

> +/*
> + * Take and release the kernel text modification lock, used for code patching.
> + * Users of this lock can sleep.
> + */
> +extern void kernel_text_lock(void);
> +extern void kernel_text_unlock(void);

Locking APIs with hidden semantics are very ugly. Remember 
lock_kernel()?

> +/*
> + * mutex protecting text section modification (dynamic code patching).
> + * some users need to sleep (allocating memory...) while they hold this lock.
> + */
> +static DEFINE_MUTEX(text_mutex);

Please update those sites to do an explicit:

	mutex_lock(&text_mutex);

instead.

That way we save a function call, and we'll also see exactly 
what type of lock is being taken, etc.

	Ingo
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