svn commit: r361138 - head/sys/compat/linuxkpi/common/include/linux

[Emmanuel Vadot]

Author: manu
Date: Sun May 17 20:09:11 2020
New Revision: 361138
URL: https://svnweb.freebsd.org/changeset/base/361138

Log:
  linuxkpi: Add atomic_dec_and_mutex_lock
  
  This function decrement the counter and if the result is 0 it acquires
  the mutex and returns 1, if not it simply returns 0.
  Needed by DRM from Linux v5.3
  
  Sponsored-by: The FreeBSD Foundation
  Differential Revision:	https://reviews.freebsd.org/D24847

Modified:
  head/sys/compat/linuxkpi/common/include/linux/mutex.h

Modified: head/sys/compat/linuxkpi/common/include/linux/mutex.h
==============================================================================
--- head/sys/compat/linuxkpi/common/include/linux/mutex.h	Sun May 17 15:32:36 2020	(r361137)
+++ head/sys/compat/linuxkpi/common/include/linux/mutex.h	Sun May 17 20:09:11 2020	(r361138)
@@ -37,6 +37,7 @@
 #include <sys/sx.h>
 
 #include <linux/spinlock.h>
+#include <asm/atomic.h>
 
 typedef struct mutex {
 	struct sx sx;
@@ -123,6 +124,16 @@ static inline bool
 mutex_is_owned(mutex_t *m)
 {
 	return (sx_xlocked(&m->sx));
+}
+
+static inline int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *m)
+{
+	if (atomic_dec_and_test(cnt)) {
+		mutex_lock(m);
+		return (1);
+	}
+
+	return (0);
 }
 
 #ifdef WITNESS_ALL