From 3f68535adad8dd89499505a65fb25d0e02d118cc Mon Sep 17 00:00:00 2001 From: john stultz Date: Wed, 21 Jan 2009 22:53:22 -0700 Subject: [PATCH] clocksource: sanity check sysfs clocksource changes Thomas, Andrew and Ingo pointed out that we don't have any safety checks in the clocksource sysfs entries to make sure sysadmins don't try to change the clocksource to a non high-res timer capable clocksource (such as jiffies) when high-res timers (HRT) is enabled. Doing so will likely hang a system. Correct this by filtering non HRT clocksources from available_clocksources and not accepting non HRT clocksources with HRT enabled. Signed-off-by: John Stultz Signed-off-by: Andrew Morton Signed-off-by: Thomas Gleixner --- include/linux/hrtimer.h | 2 +- kernel/hrtimer.c | 4 ++-- kernel/time/clocksource.c | 18 +++++++++++++++++- 3 files changed, 20 insertions(+), 4 deletions(-) diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h index 0d2f7c8a33d..58021b0c396 100644 --- a/include/linux/hrtimer.h +++ b/include/linux/hrtimer.h @@ -305,7 +305,7 @@ static inline int hrtimer_is_hres_active(struct hrtimer *timer) extern ktime_t ktime_get(void); extern ktime_t ktime_get_real(void); - +extern int hrtimer_hres_active(void); DECLARE_PER_CPU(struct tick_device, tick_cpu_device); diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c index cb8a15c1958..1a70c18cdff 100644 --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -476,7 +476,7 @@ static inline int hrtimer_is_hres_enabled(void) /* * Is the high resolution mode active ? */ -static inline int hrtimer_hres_active(void) +int hrtimer_hres_active(void) { return __get_cpu_var(hrtimer_bases).hres_active; } @@ -704,7 +704,7 @@ static int hrtimer_switch_to_hres(void) #else -static inline int hrtimer_hres_active(void) { return 0; } +int hrtimer_hres_active(void) { return 0; } static inline int hrtimer_is_hres_enabled(void) { return 0; } static inline int hrtimer_switch_to_hres(void) { return 0; } static inline void hrtimer_force_reprogram(struct hrtimer_cpu_base *base) { } diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c index 80189f6f1c5..18b9f5da4ee 100644 --- a/kernel/time/clocksource.c +++ b/kernel/time/clocksource.c @@ -30,6 +30,7 @@ #include #include /* for spin_unlock_irq() using preempt_count() m68k */ #include +#include void timecounter_init(struct timecounter *tc, const struct cyclecounter *cc, @@ -509,6 +510,18 @@ static ssize_t sysfs_override_clocksource(struct sys_device *dev, } } + /* + * Check to make sure we don't switch to a non-HRT usable + * clocksource if HRT is enabled and running + */ + if (hrtimer_hres_active() && + !(ovr->flags & CLOCK_SOURCE_VALID_FOR_HRES)) { + printk(KERN_WARNING "%s clocksource is not HRT compatible. " + "Cannot switch while in HRT mode\n", ovr->name); + ovr = NULL; + override_name[0] = 0; + } + /* Reselect, when the override name has changed */ if (ovr != clocksource_override) { clocksource_override = ovr; @@ -537,7 +550,10 @@ sysfs_show_available_clocksources(struct sys_device *dev, spin_lock_irq(&clocksource_lock); list_for_each_entry(src, &clocksource_list, list) { - count += snprintf(buf + count, + /* Don't show non-HRES clocksource if HRES is enabled */ + if (!hrtimer_hres_active() || + (src->flags & CLOCK_SOURCE_VALID_FOR_HRES)) + count += snprintf(buf + count, max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "%s ", src->name); } -- 2.39.5