linux-kernel - Re: [PATCH] docbook: some kernel-locking fixes

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Message-Id: <200804040939.01951.rusty@rustcorp.com.au>
Date:	Fri, 4 Apr 2008 09:39:01 +1000
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Randy Dunlap <rdunlap@...otime.net>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	akpm <akpm@...ux-foundation.org>, mattilinnanvuori@...oo.com
Subject: Re: [PATCH] docbook: some kernel-locking fixes

On Thursday 03 April 2008 07:47:50 Randy Dunlap wrote:
> From: Matti Linnanvuori <mattilinnanvuori@...oo.com>
> +<chapter id="try-variants">
> + <title>The try variants</title>
> +
> +  <para>
> +    <function>spin_trylock()</function> does not spin but returns non-zero
> +    if it acquires the spinlock on the first try or 0 if not.
> +  </para>
> +
> +  <para>
> +    <function>mutex_trylock()</function> does not suspend your task
> +    but returns non-zero if it could lock the mutex on the first try
> +    or 0 if not.
> +  </para>
> +
> +  <para>
> +    <function>down_trylock()</function> does not suspend your task
> +    but returns 0 if it could get the semaphore on the first try or
> +    non-zero if not. The return value is the inverse of that of
> +    <function>spin_trylock()</function> and <function>mutex_trylock()
> +    </function>.
> +  </para>
> +</chapter>

OK, other than documenting the inconsistent horror of down_trylock, I don't 
like this patch.  This document is not about documenting the functions, but 
providing an overview and pointing to them (where you can read to your 
heart's content).

This is a worthy addition, but it's a paragraph, not a chapter.  Unless you 
want to document why you would use the trylock variants (can mutex_trylock 
and down_trylock be used from interrupt context?  Or are they only useful to 
avoid deadlock?  How are they actually used in the kernel?)

Thanks,
Rusty.
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