From: peterz@infradead•org (Peter Zijlstra)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] mutex: make mutex_lock_nested an inline function
Date: Wed, 14 Oct 2015 15:47:21 +0200 [thread overview]
Message-ID: <20151014134721.GD3816@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20151014123624.GV14956@sirena.org.uk>
On Wed, Oct 14, 2015 at 01:36:24PM +0100, Mark Brown wrote:
> Sure, but I don't really expect to have to trawl the implementation of
> an API to find out about this sort of thing (I hadn't even been aware
I more like view header files as 'documentation' and c files as
implementation :-)
> that the subclasses were required to be small positive integers, never
> mind needing to check what the limit was). I think the main place I'd
> have expected to see it was in lockdep-design.txt or somewhere near
> that.
Oh, you're one of them people that actually looks in Documentation/.
> The other big one that came up recently was that lockdep apparently
> works out what a class is by looking at the point of allocation which
> causes a lot of problems for regmap since it makes all regmap locks look
> like a single class. That's fixed now by explicitly allocating a class
> per regmap with some macro magic but it was a bit of a surprise. The
> documentation doesn't make this obvious.
Yes, Documentation/locking/lockdep-design.txt needs help -- I'd even
forgotten we had it.
Does the below work for you?
---
Documentation/locking/lockdep-design.txt | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/Documentation/locking/lockdep-design.txt b/Documentation/locking/lockdep-design.txt
index 5001280e9d82..e8e9ad4e6f5e 100644
--- a/Documentation/locking/lockdep-design.txt
+++ b/Documentation/locking/lockdep-design.txt
@@ -24,6 +24,10 @@ a lock-class is used for the first time after bootup it gets registered,
and all subsequent uses of that lock-class will be attached to this
lock-class.
+A class is typically associated with a lock's initialisation site; although
+its possible to explicitly initialize a lock with a different class key --
+such class keys much come from static storage.
+
State
-----
@@ -165,6 +169,10 @@ partition.
The validator treats a lock that is taken in such a nested fashion as a
separate (sub)class for the purposes of validation.
+Since lock classes are associated with static addresses, the size of struct
+lock_class_key determines the amount of sub classes that are possible --
+currently set to 8.
+
Note: When changing code to use the _nested() primitives, be careful and
check really thoroughly that the hierarchy is correctly mapped; otherwise
you can get false positives or false negatives.
next prev parent reply other threads:[~2015-10-14 13:47 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-13 20:30 [PATCH] mutex: make mutex_lock_nested an inline function Arnd Bergmann
2015-10-13 20:38 ` Peter Zijlstra
2015-10-13 21:46 ` Arnd Bergmann
2015-10-14 8:20 ` Peter Zijlstra
2015-10-14 8:37 ` Peter Zijlstra
2015-10-14 9:00 ` Arnd Bergmann
2015-10-14 9:08 ` Peter Zijlstra
2015-10-14 9:59 ` Mark Brown
2015-10-14 10:27 ` Mark Brown
2015-10-14 11:07 ` Peter Zijlstra
2015-10-14 12:36 ` Mark Brown
2015-10-14 13:47 ` Peter Zijlstra [this message]
2015-10-14 13:50 ` Peter Zijlstra
2015-10-14 13:58 ` Ingo Molnar
2015-10-14 14:11 ` Mark Brown
2015-10-22 15:02 ` Arnd Bergmann
2015-10-22 15:09 ` Peter Zijlstra
2015-10-22 17:44 ` Russell King - ARM Linux
2015-10-27 18:13 ` Ingo Molnar
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