From 4f688d19fb9ca00acf307d1babc308157735ef0f Mon Sep 17 00:00:00 2001
From: Hans Petter Selasky <hselasky@FreeBSD.org>
Date: Thu, 9 Mar 2017 17:01:00 +0000
Subject: [PATCH] Cleanup the LinuxKPI mutex wrappers.

Add support for using mutexes during KDB and shutdown. This is also
required for doing mode-switching during panic for drm-next.

Add new mutex functions mutex_init_witness() and mutex_destroy()
allowing LinuxKPI mutexes to be tracked by witness.

Declare mutex_is_locked() and mutex_is_owned() like inline functions
to get cleaner warnings. These functions are used inside WARN_ON()
statements which might look a bit odd if these functions get fully
expanded.

Give mutexes better debug names through the mutex_name() macro when
WITNESS_ALL is defined. The mutex_name() macro can prefix parts of the
filename and line number before the mutex name.

MFC after:		1 week
Sponsored by:		Mellanox Technologies
---
 .../linuxkpi/common/include/linux/mutex.h     | 97 ++++++++++++++++---
 1 file changed, 82 insertions(+), 15 deletions(-)

diff --git a/sys/compat/linuxkpi/common/include/linux/mutex.h b/sys/compat/linuxkpi/common/include/linux/mutex.h
index 68bbfaa6059..36911b1b74c 100644
--- a/sys/compat/linuxkpi/common/include/linux/mutex.h
+++ b/sys/compat/linuxkpi/common/include/linux/mutex.h
@@ -2,7 +2,7 @@
  * Copyright (c) 2010 Isilon Systems, Inc.
  * Copyright (c) 2010 iX Systems, Inc.
  * Copyright (c) 2010 Panasas, Inc.
- * Copyright (c) 2013, 2014 Mellanox Technologies, Ltd.
+ * Copyright (c) 2013-2017 Mellanox Technologies, Ltd.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -32,6 +32,7 @@
 #define	_LINUX_MUTEX_H_
 
 #include <sys/param.h>
+#include <sys/proc.h>
 #include <sys/lock.h>
 #include <sys/sx.h>
 
@@ -41,24 +42,90 @@ typedef struct mutex {
 	struct sx sx;
 } mutex_t;
 
-#define	mutex_lock(_m)			sx_xlock(&(_m)->sx)
+/*
+ * By defining CONFIG_NO_MUTEX_SKIP LinuxKPI mutexes and asserts will
+ * not be skipped during panic().
+ */
+#ifdef CONFIG_NO_MUTEX_SKIP
+#define	MUTEX_SKIP(void) 0
+#else
+#define	MUTEX_SKIP(void) unlikely(SCHEDULER_STOPPED() || kdb_active)
+#endif
+
+#define	mutex_lock(_m) do {			\
+	if (MUTEX_SKIP())			\
+		break;				\
+	sx_xlock(&(_m)->sx);			\
+} while (0)
+
 #define	mutex_lock_nested(_m, _s)	mutex_lock(_m)
-#define	mutex_lock_interruptible(_m)	({ mutex_lock((_m)); 0; })
-#define	mutex_unlock(_m)		sx_xunlock(&(_m)->sx)
-#define	mutex_trylock(_m)		!!sx_try_xlock(&(_m)->sx)
+#define	mutex_lock_nest_lock(_m, _s)	mutex_lock(_m)
 
-#define DEFINE_MUTEX(lock)						\
-	mutex_t lock;							\
-	SX_SYSINIT_FLAGS(lock, &(lock).sx, "lnxmtx", SX_NOWITNESS)
+#define	mutex_lock_interruptible(_m) ({		\
+	MUTEX_SKIP() ? 0 :			\
+	(sx_xlock_sig(&(_m)->sx) ? -EINTR : 0);	\
+})
 
-static inline void
-linux_mutex_init(mutex_t *m)
+#define	mutex_unlock(_m) do {			\
+	if (MUTEX_SKIP())			\
+		break;				\
+	sx_xunlock(&(_m)->sx);			\
+} while (0)
+
+#define	mutex_trylock(_m) ({			\
+	MUTEX_SKIP() ? 1 :			\
+	!!sx_try_xlock(&(_m)->sx);		\
+})
+
+#define	mutex_init(_m) \
+	linux_mutex_init(_m, mutex_name(#_m), SX_NOWITNESS)
+
+#define	mutex_init_witness(_m) \
+	linux_mutex_init(_m, mutex_name(#_m), SX_DUPOK)
+
+#define	mutex_destroy(_m) \
+	linux_mutex_destroy(_m)
+
+static inline bool
+mutex_is_locked(mutex_t *m)
 {
-
-	memset(&m->sx, 0, sizeof(m->sx));
-	sx_init_flags(&m->sx, "lnxmtx",  SX_NOWITNESS);
+	return ((struct thread *)SX_OWNER(m->sx.sx_lock) != NULL);
 }
 
-#define	mutex_init(m)	linux_mutex_init(m)
+static inline bool
+mutex_is_owned(mutex_t *m)
+{
+	return (sx_xlocked(&m->sx));
+}
 
-#endif	/* _LINUX_MUTEX_H_ */
+#ifdef WITNESS_ALL
+/* NOTE: the maximum WITNESS name is 64 chars */
+#define	__mutex_name(name, file, line)		\
+	(((const char *){file ":" #line "-" name}) + 	\
+	(sizeof(file) > 16 ? sizeof(file) - 16 : 0))
+#else
+#define	__mutex_name(name, file, line)	name
+#endif
+#define	_mutex_name(...)	__mutex_name(__VA_ARGS__)
+#define	mutex_name(name)	_mutex_name(name, __FILE__, __LINE__)
+
+#define	DEFINE_MUTEX(lock)						\
+	mutex_t lock;							\
+	SX_SYSINIT_FLAGS(lock, &(lock).sx, mutex_name(#lock), SX_DUPOK)
+
+static inline void
+linux_mutex_init(mutex_t *m, const char *name, int flags)
+{
+	memset(m, 0, sizeof(*m));
+	sx_init_flags(&m->sx, name, flags);
+}
+
+static inline void
+linux_mutex_destroy(mutex_t *m)
+{
+	if (mutex_is_owned(m))
+		mutex_unlock(m);
+	sx_destroy(&m->sx);
+}
+
+#endif					/* _LINUX_MUTEX_H_ */