2020-01-29 18:17:59

by Davidlohr Bueso

Subject: [PATCH] security, keys: Optimize barrier usage for Rmw atomic bitops

For both set and clear_bit, we can avoid the unnecessary barriers
on non LL/SC architectures, such as x86. Instead, use the
smp_mb__{before,after}_atomic() calls.

Signed-off-by: Davidlohr Bueso <[email protected]>
---
security/keys/gc.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/security/keys/gc.c b/security/keys/gc.c
index 671dd730ecfc..ce7b4c22e3c4 100644
--- a/security/keys/gc.c
+++ b/security/keys/gc.c
@@ -102,7 +102,7 @@ void key_gc_keytype(struct key_type *ktype)

key_gc_dead_keytype = ktype;
set_bit(KEY_GC_REAPING_KEYTYPE, &key_gc_flags);
- smp_mb();
+ smp_mb__after_atomic();
set_bit(KEY_GC_REAP_KEYTYPE, &key_gc_flags);

kdebug("schedule");
@@ -308,7 +308,7 @@ static void key_garbage_collector(struct work_struct *work)

if (unlikely(gc_state & KEY_GC_REAPING_DEAD_3)) {
kdebug("dead wake");
- smp_mb();
+ smp_mb__before_atomic();
clear_bit(KEY_GC_REAPING_KEYTYPE, &key_gc_flags);
wake_up_bit(&key_gc_flags, KEY_GC_REAPING_KEYTYPE);
}
--
2.16.4

2020-03-20 17:11:34

by Davidlohr Bueso

Subject: Re: [PATCH] security, keys: Optimize barrier usage for Rmw atomic bitops

ping?

On Wed, 29 Jan 2020, Davidlohr Bueso wrote:

>For both set and clear_bit, we can avoid the unnecessary barriers
>on non LL/SC architectures, such as x86. Instead, use the
>smp_mb__{before,after}_atomic() calls.
>
>Signed-off-by: Davidlohr Bueso <[email protected]>
>---
> security/keys/gc.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
>diff --git a/security/keys/gc.c b/security/keys/gc.c
>index 671dd730ecfc..ce7b4c22e3c4 100644
>--- a/security/keys/gc.c
>+++ b/security/keys/gc.c
>@@ -102,7 +102,7 @@ void key_gc_keytype(struct key_type *ktype)
>
> key_gc_dead_keytype = ktype;
> set_bit(KEY_GC_REAPING_KEYTYPE, &key_gc_flags);
>- smp_mb();
>+ smp_mb__after_atomic();
> set_bit(KEY_GC_REAP_KEYTYPE, &key_gc_flags);
>
> kdebug("schedule");
>@@ -308,7 +308,7 @@ static void key_garbage_collector(struct work_struct *work)
>
> if (unlikely(gc_state & KEY_GC_REAPING_DEAD_3)) {
> kdebug("dead wake");
>- smp_mb();
>+ smp_mb__before_atomic();
> clear_bit(KEY_GC_REAPING_KEYTYPE, &key_gc_flags);
> wake_up_bit(&key_gc_flags, KEY_GC_REAPING_KEYTYPE);
> }
>--
>2.16.4
>