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authorMark Rutland <mark.rutland@arm.com>2018-06-21 13:13:06 +0100
committerIngo Molnar <mingo@kernel.org>2018-06-21 14:22:33 +0200
commitf74445b6dd6b8f33ed34e005d19ecbb49171dabf (patch)
tree5e12a311221be0cd9bd0e34ae0f910b56cc5a116 /net/atm/pppoatm.c
parent8b47038e6d349cca950e75076566a0de990c4645 (diff)
downloadlinux-stericsson-f74445b6dd6b8f33ed34e005d19ecbb49171dabf.tar.gz
atomics/treewide: Remove atomic_inc_not_zero_hint()
While documentation suggests atomic_inc_not_zero_hint() will perform better than atomic_inc_not_zero(), this is unlikely to be the case. No architectures implement atomic_inc_not_zero_hint() directly, and thus it either falls back to atomic_inc_not_zero(), or a loop using atomic_cmpxchg(). Whenever the hint does not match the value in memory, the repeated use of atomic_cmpxchg() will be more expensive than the read that atomic_inc_not_zero_hint() attempts to avoid. For architectures with LL/SC atomics, a read cannot be avoided, and it would always be better to use atomic_inc_not_zero() directly. For other architectures, their own atomic_inc_not_zero() is likely to be more optimal than an atomic_cmpxchg() loop regardless. Generally, atomic_inc_not_zero_hint() is liable to perform worse than atomic_inc_not_zero(). Further, atomic_inc_not_zero_hint() only exists for atomic_t, and not atomic64_t or atomic_long_t, and there is only one user in the kernel tree. Given all this, let's remove atomic_inc_not_zero_hint(), and migrate the existing user over to atomic_inc_not_zero(). There should be no functional change as a result of this patch. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Reviewed-by: Will Deacon <will.deacon@arm.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/lkml/20180621121321.4761-4-mark.rutland@arm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'net/atm/pppoatm.c')
-rw-r--r--net/atm/pppoatm.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/net/atm/pppoatm.c b/net/atm/pppoatm.c
index af8c4b38b746..d84227d75717 100644
--- a/net/atm/pppoatm.c
+++ b/net/atm/pppoatm.c
@@ -244,7 +244,7 @@ static int pppoatm_may_send(struct pppoatm_vcc *pvcc, int size)
* the packet count limit, so...
*/
if (atm_may_send(pvcc->atmvcc, size) &&
- atomic_inc_not_zero_hint(&pvcc->inflight, NONE_INFLIGHT))
+ atomic_inc_not_zero(&pvcc->inflight))
return 1;
/*