linux-kernel - [PATCH-tip 3/5] locking/ww_mutex: Remove DEFINE_WW

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Message-Id: <20210318172814.4400-4-longman@redhat.com>
Date:   Thu, 18 Mar 2021 13:28:12 -0400
From:   Waiman Long <longman@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Davidlohr Bueso <dave@...olabs.net>
Cc:     linux-kernel@...r.kernel.org, Juri Lelli <juri.lelli@...hat.com>,
        Waiman Long <longman@...hat.com>
Subject: [PATCH-tip 3/5] locking/ww_mutex: Remove DEFINE_WW_MUTEX() macro

The current DEFINE_WW_MUTEX() macro fails to properly set up the lockdep
key of the ww_mutexes causing potential circular locking dependency
splat. Though it is possible to add more macro magic to make it work,
but the result is rather ugly.

Since locktorture was the only user of DEFINE_WW_MUTEX() and the
previous commit has just removed its use. It is easier to just remove
the macro to force future users of ww_mutexes to use ww_mutex_init()
for initialization.

Suggested-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Waiman Long <longman@...hat.com>
---
 include/linux/ww_mutex.h | 17 ++---------------
 1 file changed, 2 insertions(+), 15 deletions(-)

diff --git a/include/linux/ww_mutex.h b/include/linux/ww_mutex.h
index 6ecf2a0220db..b77f39f319ad 100644
--- a/include/linux/ww_mutex.h
+++ b/include/linux/ww_mutex.h
@@ -48,39 +48,26 @@ struct ww_acquire_ctx {
 #endif
 };
 
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
-# define __WW_CLASS_MUTEX_INITIALIZER(lockname, class) \
-		, .ww_class = class
-#else
-# define __WW_CLASS_MUTEX_INITIALIZER(lockname, class)
-#endif
-
 #define __WW_CLASS_INITIALIZER(ww_class, _is_wait_die)	    \
 		{ .stamp = ATOMIC_LONG_INIT(0) \
 		, .acquire_name = #ww_class "_acquire" \
 		, .mutex_name = #ww_class "_mutex" \
 		, .is_wait_die = _is_wait_die }
 
-#define __WW_MUTEX_INITIALIZER(lockname, class) \
-		{ .base =  __MUTEX_INITIALIZER(lockname.base) \
-		__WW_CLASS_MUTEX_INITIALIZER(lockname, class) }
-
 #define DEFINE_WD_CLASS(classname) \
 	struct ww_class classname = __WW_CLASS_INITIALIZER(classname, 1)
 
 #define DEFINE_WW_CLASS(classname) \
 	struct ww_class classname = __WW_CLASS_INITIALIZER(classname, 0)
 
-#define DEFINE_WW_MUTEX(mutexname, ww_class) \
-	struct ww_mutex mutexname = __WW_MUTEX_INITIALIZER(mutexname, ww_class)
-
 /**
  * ww_mutex_init - initialize the w/w mutex
  * @lock: the mutex to be initialized
  * @ww_class: the w/w class the mutex should belong to
  *
  * Initialize the w/w mutex to unlocked state and associate it with the given
- * class.
+ * class. Static define macro for w/w mutex is not provided and this function
+ * is the only way to properly initialize the w/w mutex.
  *
  * It is not allowed to initialize an already locked mutex.
  */
-- 
2.18.1