[Intel-gfx] [PATCH 3/3] x86, pat: Convert memtype_lock spinlock to a rwlock

[Chris Wilson]

Presuming that we lookup the memtype of an address far more often than
we modify the PAT ranges, favour the reader.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 arch/x86/mm/pat.c |   20 ++++++++++----------
 1 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 18d4aa9..8cc67e5 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -130,7 +130,7 @@ void pat_init(void)
 
 #undef PAT
 
-static DEFINE_SPINLOCK(memtype_lock);	/* protects memtype accesses */
+static DEFINE_RWLOCK(memtype_lock);	/* protects memtype accesses */
 
 /*
  * Does intersection of PAT memory type and MTRR memory type and returns
@@ -310,7 +310,7 @@ int reserve_memtype(u64 start, u64 end, unsigned long req_type,
 	new->end	= end;
 	new->type	= actual_type;
 
-	spin_lock(&memtype_lock);
+	write_lock(&memtype_lock);
 
 	err = rbt_memtype_check_insert(new, new_type);
 	if (err) {
@@ -318,12 +318,12 @@ int reserve_memtype(u64 start, u64 end, unsigned long req_type,
 		       "track %s, req %s\n",
 		       start, end, cattr_name(new->type), cattr_name(req_type));
 		kfree(new);
-		spin_unlock(&memtype_lock);
+		write_unlock(&memtype_lock);
 
 		return err;
 	}
 
-	spin_unlock(&memtype_lock);
+	write_unlock(&memtype_lock);
 
 	dprintk("reserve_memtype added 0x%Lx-0x%Lx, track %s, req %s, ret %s\n",
 		start, end, cattr_name(new->type), cattr_name(req_type),
@@ -355,9 +355,9 @@ int free_memtype(u64 start, u64 end)
 		return -EINVAL;
 	}
 
-	spin_lock(&memtype_lock);
+	write_lock(&memtype_lock);
 	entry = rbt_memtype_erase(start, end);
-	spin_unlock(&memtype_lock);
+	write_unlock(&memtype_lock);
 
 	if (!entry) {
 		printk(KERN_INFO "%s:%d freeing invalid memtype %Lx-%Lx\n",
@@ -390,13 +390,13 @@ static unsigned long lookup_memtype(u64 paddr)
 	if (x86_platform.is_untracked_pat_range(paddr, paddr + PAGE_SIZE))
 		return _PAGE_CACHE_WB;
 
-	spin_lock(&memtype_lock);
+	read_lock(&memtype_lock);
 
 	entry = rbt_memtype_lookup(paddr);
 	if (entry != NULL)
 		rettype = entry->type;
 
-	spin_unlock(&memtype_lock);
+	read_unlock(&memtype_lock);
 
 	if (rettype != -1)
 		return rettype;
@@ -754,9 +754,9 @@ static struct memtype *memtype_get_idx(loff_t pos)
 	if (!print_entry)
 		return NULL;
 
-	spin_lock(&memtype_lock);
+	read_lock(&memtype_lock);
 	ret = rbt_memtype_copy_nth_element(print_entry, pos);
-	spin_unlock(&memtype_lock);
+	read_unlock(&memtype_lock);
 
 	if (!ret) {
 		return print_entry;
-- 
1.7.5.4