Add __this_cpu_try_cmpxchg() version of the percpu op.
Signed-off-by: Uros Bizjak <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Uladzislau Rezki <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Dennis Zhou <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Christoph Lameter <[email protected]>
---
include/linux/percpu-defs.h | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/include/linux/percpu-defs.h b/include/linux/percpu-defs.h
index ec3573119923..8efce7414fad 100644
--- a/include/linux/percpu-defs.h
+++ b/include/linux/percpu-defs.h
@@ -475,6 +475,12 @@ do { \
raw_cpu_cmpxchg(pcp, oval, nval); \
})
+#define __this_cpu_try_cmpxchg(pcp, ovalp, nval) \
+({ \
+ __this_cpu_preempt_check("try_cmpxchg"); \
+ raw_cpu_try_cmpxchg(pcp, ovalp, nval); \
+})
+
#define __this_cpu_sub(pcp, val) __this_cpu_add(pcp, -(typeof(pcp))(val))
#define __this_cpu_inc(pcp) __this_cpu_add(pcp, 1)
#define __this_cpu_dec(pcp) __this_cpu_sub(pcp, 1)
--
2.45.1
Use __this_cpu_try_cmpxchg() instead of
__this_cpu_cmpxchg (*ptr, old, new) == old in
preload_this_cpu_lock(). x86 CMPXCHG instruction returns
success in ZF flag, so this change saves a compare after cmpxchg.
No functional change intended.
Signed-off-by: Uros Bizjak <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Uladzislau Rezki <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Dennis Zhou <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: Christoph Lameter <[email protected]>
---
mm/vmalloc.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 6641be0ca80b..0120faee5471 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1816,7 +1816,7 @@ static void free_vmap_area(struct vmap_area *va)
static inline void
preload_this_cpu_lock(spinlock_t *lock, gfp_t gfp_mask, int node)
{
- struct vmap_area *va = NULL;
+ struct vmap_area *va = NULL, *tmp;
/*
* Preload this CPU with one extra vmap_area object. It is used
@@ -1832,7 +1832,8 @@ preload_this_cpu_lock(spinlock_t *lock, gfp_t gfp_mask, int node)
spin_lock(lock);
- if (va && __this_cpu_cmpxchg(ne_fit_preload_node, NULL, va))
+ tmp = NULL;
+ if (va && !__this_cpu_try_cmpxchg(ne_fit_preload_node, &tmp, va))
kmem_cache_free(vmap_area_cachep, va);
}
--
2.45.1
> Use __this_cpu_try_cmpxchg() instead of
> __this_cpu_cmpxchg (*ptr, old, new) == old in
> preload_this_cpu_lock(). x86 CMPXCHG instruction returns
> success in ZF flag, so this change saves a compare after cmpxchg.
>
Just a small note. Can you also add a tiny difference in assembly
language where it is visible? I mean update a commit message.
--
Uladzislau Rezki