From 8f4c344696b9f9f8471d7f342076ef10ed7f66a5 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Thu, 19 Sep 2013 19:06:46 +0100 Subject: [PATCH] lockref: use cmpxchg64 explicitly for lockless updates The cmpxchg() function tends not to support 64-bit arguments on 32-bit architectures. This could be either due to use of unsigned long arguments (like on ARM) or lack of instruction support (cmpxchgq on x86). However, these architectures may implement a specific cmpxchg64() function to provide 64-bit cmpxchg support instead. Since the lockref code requires a 64-bit cmpxchg and relies on the architecture selecting ARCH_USE_CMPXCHG_LOCKREF, move to using cmpxchg64 instead of cmpxchg and allow 32-bit architectures to make use of the lockless lockref implementation. Cc: Waiman Long Signed-off-by: Will Deacon Signed-off-by: Linus Torvalds --- lib/lockref.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/lib/lockref.c b/lib/lockref.c index e2cd2c0a8821..677d036cf3c7 100644 --- a/lib/lockref.c +++ b/lib/lockref.c @@ -14,8 +14,8 @@ while (likely(arch_spin_value_unlocked(old.lock.rlock.raw_lock))) { \ struct lockref new = old, prev = old; \ CODE \ - old.lock_count = cmpxchg(&lockref->lock_count, \ - old.lock_count, new.lock_count); \ + old.lock_count = cmpxchg64(&lockref->lock_count, \ + old.lock_count, new.lock_count); \ if (likely(old.lock_count == prev.lock_count)) { \ SUCCESS; \ } \ -- 2.20.1