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Date: Tue, 3 Mar 2009 01:32:37 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Masami Hiramatsu <mhiramat@redhat.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       Nick Piggin <npiggin@suse.de>, Steven Rostedt <rostedt@goodmis.org>,
       Andi Kleen <andi@firstfloor.org>, linux-kernel@vger.kernel.org,
       Thomas Gleixner <tglx@linutronix.de>,
       Peter Zijlstra <peterz@infradead.org>,
       Frederic Weisbecker <fweisbec@gmail.com>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Arjan van de Ven <arjan@infradead.org>,
       Rusty Russell <rusty@rustcorp.com.au>, "H. Peter Anvin" <hpa@zytor.com>,
       Steven Rostedt <srostedt@redhat.com>
Subject: Re: [PATCH] Text Edit Lock - Architecture Independent Code
Message-ID: <20090303003237.GA30221@elte.hu>
References: <49A853CD.3020607@redhat.com> <49AC10E9.1090102@redhat.com> <20090302171914.GB21735@Krystal> <49AC5A87.7000604@redhat.com> <20090302222254.GA31962@elte.hu> <49AC63FA.70801@redhat.com> <20090302230915.GA11626@elte.hu> <49AC6DEA.2050304@redhat.com> <20090302234910.GA17956@elte.hu> <20090303000054.GC3906@Krystal>
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* Mathieu Desnoyers <mathieu.desnoyers@polymtl.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