From 8cab02dc3c58a12235c6d463ce684dded9696848 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Thu, 20 Aug 2009 18:19:45 +0200 Subject: [PATCH] x86: Do not unregister PIT clocksource on PIT oneshot setup/shutdown This basically reverts commit 1a0c009ac (x86: unregister PIT clocksource when PIT is disabled) because the problem which was tried to address with that patch has been solved by commit 3f68535ada (clocksource: sanity check sysfs clocksource changes). The problem addressed by the original patch is that PIT could be selected as clocksource after the system switched the PIT off or set the PIT into one shot mode which would result in complete timekeeping wreckage. Now with the sysfs sanity check in place PIT cannot be selected again when the system is in oneshot mode. The system will not switch to one shot mode as long as PIT is installed because PIT is not suitable for one shot. The shutdown case which happens when the lapic timer is installed is covered by the fact that init_pit_clocksource() is called after the lapic timer take over and then does not install the PIT clocksource at all. We should have done the sanity checks back then, but ... This also solves the locking problem which was reported vs. the clocksource rework. LKML-Reference: Cc: Martin Schwidefsky Cc: john stultz Signed-off-by: Thomas Gleixner --- arch/x86/kernel/i8253.c | 19 ------------------- 1 file changed, 19 deletions(-) diff --git a/arch/x86/kernel/i8253.c b/arch/x86/kernel/i8253.c index 5cf36c053ac..23c167925a5 100644 --- a/arch/x86/kernel/i8253.c +++ b/arch/x86/kernel/i8253.c @@ -19,12 +19,6 @@ DEFINE_SPINLOCK(i8253_lock); EXPORT_SYMBOL(i8253_lock); -#ifdef CONFIG_X86_32 -static void pit_disable_clocksource(void); -#else -static inline void pit_disable_clocksource(void) { } -#endif - /* * HPET replaces the PIT, when enabled. So we need to know, which of * the two timers is used @@ -57,12 +51,10 @@ static void init_pit_timer(enum clock_event_mode mode, outb_pit(0, PIT_CH0); outb_pit(0, PIT_CH0); } - pit_disable_clocksource(); break; case CLOCK_EVT_MODE_ONESHOT: /* One shot setup */ - pit_disable_clocksource(); outb_pit(0x38, PIT_MODE); break; @@ -200,17 +192,6 @@ static struct clocksource pit_cs = { .shift = 20, }; -static void pit_disable_clocksource(void) -{ - /* - * Use mult to check whether it is registered or not - */ - if (pit_cs.mult) { - clocksource_unregister(&pit_cs); - pit_cs.mult = 0; - } -} - static int __init init_pit_clocksource(void) { /*