change from rwlock(9) to mutex(9) for linux rwlocks

Linux rwlocks are read/write spin locks which don't sleep.
Fixes a panic claudio@ reported with a WITNESS kernel on inteldrm(4)
'panic: acquiring blockable sleep lock with spinlock or critical section
held (rwlock) drmvma'

Patch from kettenis@ with a small tweak from me.  ok kettenis@

3 files changed, 7 insertions, 11 deletions

diff --git a/sys/dev/pci/drm/include/drm/drm_vma_manager.h b/sys/dev/pci/drm/include/drm/drm_vma_manager.h
index 42a848898f2..3d8c827e322 100644
--- a/sys/dev/pci/drm/include/drm/drm_vma_manager.h
+++ b/sys/dev/pci/drm/include/drm/drm_vma_manager.h
@@ -50,14 +50,14 @@ struct drm_vma_offset_file {
 };
 
 struct drm_vma_offset_node {
-	rwlock_t vm_lock;
+	struct mutex vm_lock;
 	struct drm_mm_node vm_node;
 	struct rb_root vm_files;
 	bool readonly:1;
 };
 
 struct drm_vma_offset_manager {
-	rwlock_t vm_lock;
+	struct mutex vm_lock;
 	struct drm_mm vm_addr_space_mm;
 };
 
@@ -148,7 +148,7 @@ static inline void drm_vma_node_reset(struct drm_vma_offset_node *node)
 {
 	memset(node, 0, sizeof(*node));
 	node->vm_files = RB_ROOT;
-	rw_init(&node->vm_lock, "drmvma");
+	mtx_init(&node->vm_lock, IPL_NONE);
 }
 
 /**
diff --git a/sys/dev/pci/drm/include/linux/rwlock_types.h b/sys/dev/pci/drm/include/linux/rwlock_types.h
index 36b1f7feab1..b2b62469f0d 100644
--- a/sys/dev/pci/drm/include/linux/rwlock_types.h
+++ b/sys/dev/pci/drm/include/linux/rwlock_types.h
@@ -3,8 +3,4 @@
 #ifndef _LINUX_RWLOCK_TYPES_H
 #define _LINUX_RWLOCK_TYPES_H
 
-#include <sys/rwlock.h>
-
-typedef struct rwlock rwlock_t;
-
 #endif
diff --git a/sys/dev/pci/drm/include/linux/spinlock.h b/sys/dev/pci/drm/include/linux/spinlock.h
index 7bc26e1beac..b4bf1ba8015 100644
--- a/sys/dev/pci/drm/include/linux/spinlock.h
+++ b/sys/dev/pci/drm/include/linux/spinlock.h
@@ -55,9 +55,9 @@ atomic_dec_and_lock(volatile int *v, struct mutex *mtxp)
 #define assert_spin_locked(mtxp)	MUTEX_ASSERT_LOCKED(mtxp)
 #define spin_trylock_irq(mtxp)		mtx_enter_try(mtxp)
 
-#define read_lock(rwl)			rw_enter_read(rwl)
-#define read_unlock(rwl)		rw_exit_read(rwl)
-#define write_lock(rwl)			rw_enter_write(rwl)
-#define write_unlock(rwl)		rw_exit_write(rwl)
+#define read_lock(mtxp)			mtx_enter(mtxp)
+#define read_unlock(mtxp)		mtx_leave(mtxp)
+#define write_lock(mtxp)		mtx_enter(mtxp)
+#define write_unlock(mtxp)		mtx_leave(mtxp)
 
 #endif