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

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Date:	Mon, 2 Mar 2009 19:39:28 -0500
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	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

* Ingo Molnar (mingo@...e.hu) wrote:
> 
> * 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.
> 

OK. However we'll have to export the text_mutex symbol and use it in
various locations. As long as we are fine with that, I'll provide an
updated patch.

Mathieu

> 	Ingo

-- 
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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