From 0f049e6e2b4919250b1c66fabdbf8d812aa43880 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Fri, 23 Mar 2012 16:13:29 +0100 Subject: [PATCH] x86/hpet: simplify hpet_get_channel() There's no need for a lock here, elimination of which makes the function a leaf one, thus allowing for better (and smaller) code. Further, use the variable next_channel according to its name - so far it represented the most recently used channel rather than the next one to use. Signed-off-by: Jan Beulich Acked-by: Keir Fraser --- xen/arch/x86/hpet.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/xen/arch/x86/hpet.c b/xen/arch/x86/hpet.c index b17cd07497..8ead34be60 100644 --- a/xen/arch/x86/hpet.c +++ b/xen/arch/x86/hpet.c @@ -402,16 +402,17 @@ static void __init hpet_fsb_cap_lookup(void) static struct hpet_event_channel *hpet_get_channel(unsigned int cpu) { static unsigned int next_channel; - static spinlock_t next_lock = SPIN_LOCK_UNLOCKED; unsigned int i, next; struct hpet_event_channel *ch; if ( num_hpets_used == 0 ) return hpet_events; - spin_lock(&next_lock); - next = next_channel = (next_channel + 1) % num_hpets_used; - spin_unlock(&next_lock); + do { + next = next_channel; + if ( (i = next + 1) == num_hpets_used ) + i = 0; + } while ( cmpxchg(&next_channel, next, i) != next ); /* try unused channel first */ for ( i = next; i < next + num_hpets_used; i++ ) -- 2.30.2