From: Uros Bizjak Date: Mon, 22 Aug 2022 14:32:43 +0000 (+0200) Subject: netdev: Use try_cmpxchg in napi_if_scheduled_mark_missed X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=b9030780971b56c0c455c3b66244efd96608846d;p=linux.git netdev: Use try_cmpxchg in napi_if_scheduled_mark_missed Use try_cmpxchg instead of cmpxchg (*ptr, old, new) == old in napi_if_scheduled_mark_missed. x86 CMPXCHG instruction returns success in ZF flag, so this change saves a compare after cmpxchg (and related move instruction in front of cmpxchg). Also, try_cmpxchg implicitly assigns old *ptr value to "old" when cmpxchg fails, enabling further code simplifications. Cc: Eric Dumazet Cc: Paolo Abeni Signed-off-by: Uros Bizjak Link: https://lore.kernel.org/r/20220822143243.2798-1-ubizjak@gmail.com Signed-off-by: Jakub Kicinski --- diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 64e8662632f84..8839abc1f941a 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -546,8 +546,8 @@ static inline bool napi_if_scheduled_mark_missed(struct napi_struct *n) { unsigned long val, new; + val = READ_ONCE(n->state); do { - val = READ_ONCE(n->state); if (val & NAPIF_STATE_DISABLE) return true; @@ -555,7 +555,7 @@ static inline bool napi_if_scheduled_mark_missed(struct napi_struct *n) return false; new = val | NAPIF_STATE_MISSED; - } while (cmpxchg(&n->state, val, new) != val); + } while (!try_cmpxchg(&n->state, &val, new)); return true; }