Date: Tue, 30 May 2006 23:06:25 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org, Arjan van de Ven <arjan@infradead.org>,
       Andrew Morton <akpm@osdl.org>
Subject: Re: [patch 38/61] lock validator: special locking: i_mutex
Message-ID: <20060530210625.GB28618@elte.hu>
References: <20060529212613.GL3155@elte.hu> <1149022401.21827.6.camel@localhost.localdomain>
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* Steven Rostedt <rostedt@goodmis.org> wrote:

> On Mon, 2006-05-29 at 23:26 +0200, Ingo Molnar wrote:
> > + * inode->i_mutex nesting types for the LOCKDEP validator:
> > + *
> > + * 0: the object of the current VFS operation
> > + * 1: parent
> > + * 2: child/target
> > + */
> > +enum inode_i_mutex_lock_type
> > +{
> > +       I_MUTEX_NORMAL,
> > +       I_MUTEX_PARENT,
> > +       I_MUTEX_CHILD
> > +};
> > +
> > +/* 
> 
> I guess we can say the same about I_MUTEX_NORMAL.

yeah. Subtypes start from 1, as 0 is the basic type.

Lock types are keyed via static kernel addresses. This means that we can 
use the lock address (for DEFINE_SPINLOCK) or the static key embedded in 
spin_lock_init() as a key in 99% of the cases. The key [struct 
lockdep_type_key, see include/linux/lockdep.h] occupies enough bytes (of 
kernel static virtual memory) so that the keys remain automatically 
unique. Right now MAX_LOKCDEP_SUBTYPES is 8, so the keys take at most 8 
bytes. (To save some memory there's another detail: for static locks 
(DEFINE_SPINLOCK ones) we use the lock address itself as the key.)

	Ingo
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