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Date:   Wed, 17 Mar 2021 18:40:27 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Waiman Long <longman@redhat.com>
Cc:     linux-kernel@vger.kernel.org, linux-tip-commits@vger.kernel.org,
        Ingo Molnar <mingo@kernel.org>, x86@kernel.org
Subject: Re: [tip: locking/urgent] locking/ww_mutex: Treat ww_mutex_lock()
 like a trylock
Message-ID: <YFI/C4VZuWjyHLNK@hirez.programming.kicks-ass.net>
References: <20210316153119.13802-4-longman@redhat.com>
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 <e1bcd7fb-3a40-f207-ee19-d276c8b8bb75@redhat.com>
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On Wed, Mar 17, 2021 at 05:48:48PM +0100, Peter Zijlstra wrote:

> I think you'll find that if you use ww_mutex_init() it'll all work. Let
> me go and zap this patch, and then I'll try and figure out why
> DEFINE_WW_MUTEX() is buggered.

Moo, I can't get the compiler to do as I want :/

The below is so close but doesn't actually compile.. Maybe we should
just give up on DEFINE_WW_MUTEX and simply remove it.

---
diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index 0cd631a19727..85f50538f26a 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -129,12 +129,15 @@ do {									\
 # define __DEP_MAP_MUTEX_INITIALIZER(lockname)
 #endif
 
-#define __MUTEX_INITIALIZER(lockname) \
+#define ___MUTEX_INITIALIZER(lockname, depmap) \
 		{ .owner = ATOMIC_LONG_INIT(0) \
 		, .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
 		, .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
 		__DEBUG_MUTEX_INITIALIZER(lockname) \
-		__DEP_MAP_MUTEX_INITIALIZER(lockname) }
+		depmap }
+
+#define __MUTEX_INITIALIZER(lockname) \
+		___MUTEX_INITIALIZER(lockname, __DEP_MAP_MUTEX_INITIALIZER(lockname))
 
 #define DEFINE_MUTEX(mutexname) \
 	struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
diff --git a/include/linux/ww_mutex.h b/include/linux/ww_mutex.h
index 6ecf2a0220db..c62a030652b4 100644
--- a/include/linux/ww_mutex.h
+++ b/include/linux/ww_mutex.h
@@ -50,9 +50,17 @@ struct ww_acquire_ctx {
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 # define __WW_CLASS_MUTEX_INITIALIZER(lockname, class) \
-		, .ww_class = class
+		, .ww_class = &(class)
+
+# define __DEP_MAP_WW_MUTEX_INITIALIZER(lockname, class) \
+		, .dep_map = { \
+			.key = &(class).mutex_key, \
+			.name = (class).mutex_name, \
+			.wait_type_inner = LD_WAIT_SLEEP, \
+		}
 #else
 # define __WW_CLASS_MUTEX_INITIALIZER(lockname, class)
+# define __DEP_MAP_WW_MUTEX_INITIALIZER(lockname, class)
 #endif
 
 #define __WW_CLASS_INITIALIZER(ww_class, _is_wait_die)	    \
@@ -62,7 +70,8 @@ struct ww_acquire_ctx {
 		, .is_wait_die = _is_wait_die }
 
 #define __WW_MUTEX_INITIALIZER(lockname, class) \
-		{ .base =  __MUTEX_INITIALIZER(lockname.base) \
+		{ .base =  ___MUTEX_INITIALIZER(lockname.base, \
+			__DEP_MAP_WW_MUTEX_INITIALIZER(lockname.base, class)) \
 		__WW_CLASS_MUTEX_INITIALIZER(lockname, class) }
 
 #define DEFINE_WD_CLASS(classname) \
diff --git a/kernel/locking/locktorture.c b/kernel/locking/locktorture.c
index 0ab94e1f1276..e8305233eb0b 100644
--- a/kernel/locking/locktorture.c
+++ b/kernel/locking/locktorture.c
@@ -358,9 +358,9 @@ static struct lock_torture_ops mutex_lock_ops = {
 
 #include <linux/ww_mutex.h>
 static DEFINE_WD_CLASS(torture_ww_class);
-static DEFINE_WW_MUTEX(torture_ww_mutex_0, &torture_ww_class);
-static DEFINE_WW_MUTEX(torture_ww_mutex_1, &torture_ww_class);
-static DEFINE_WW_MUTEX(torture_ww_mutex_2, &torture_ww_class);
+static DEFINE_WW_MUTEX(torture_ww_mutex_0, torture_ww_class);
+static DEFINE_WW_MUTEX(torture_ww_mutex_1, torture_ww_class);
+static DEFINE_WW_MUTEX(torture_ww_mutex_2, torture_ww_class);
 
 static int torture_ww_mutex_lock(void)
 __acquires(torture_ww_mutex_0)