Commit b9030780 authored by Uros Bizjak's avatar Uros Bizjak Committed by Jakub Kicinski

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 <edumazet@google.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: default avatarUros Bizjak <ubizjak@gmail.com>
Link: https://lore.kernel.org/r/20220822143243.2798-1-ubizjak@gmail.comSigned-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 2c58a914
......@@ -546,8 +546,8 @@ static inline bool napi_if_scheduled_mark_missed(struct napi_struct *n)
{
unsigned long val, new;
do {
val = READ_ONCE(n->state);
do {
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;
}
......
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