OF: convert devtree lock from rw_lock to raw spinlock

With the locking cleanup in place (from "OF: Fixup resursive
locking code paths"), we can now do the conversion from the
rw_lock to a raw spinlock as required for preempt-rt.

The previous cleanup and this conversion were originally
separate since they predated when mainline got raw spinlock (in
commit c2f21ce2e31286a "locking: Implement new raw_spinlock").

So, at that point in time, the cleanup was considered plausible
for mainline, but not this conversion.  In any case, we've kept
them separate as it makes for easier review and better bisection.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[PG: taken from preempt-rt, update subject & add a commit log]
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Rob Herring <rob.herring@calxeda.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/sparc/kernel/prom_common.c b/arch/sparc/kernel/prom_common.c
index 1303021748c8..9f20566b0773 100644
--- a/arch/sparc/kernel/prom_common.c
+++ b/arch/sparc/kernel/prom_common.c
@@ -64,7 +64,7 @@ int of_set_property(struct device_node *dp, const char *name, void *val, int len
         err = -ENODEV;
 
         mutex_lock(&of_set_property_mutex);
-        write_lock(&devtree_lock);
+        raw_spin_lock(&devtree_lock);
         prevp = &dp->properties;
         while (*prevp) {
                 struct property *prop = *prevp;
@@ -91,7 +91,7 @@ int of_set_property(struct device_node *dp, const char *name, void *val, int len
                 }
                 prevp = &(*prevp)->next;
         }
-        write_unlock(&devtree_lock);
+        raw_spin_unlock(&devtree_lock);
         mutex_unlock(&of_set_property_mutex);
 
         /* XXX Upate procfs if necessary... */