From acb04058de49458010c44bb35b849d45113fd668 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 19 Jan 2017 14:36:33 +0100 Subject: sched/clock: Fix hotplug crash Mike reported that he could trigger the WARN_ON_ONCE() in set_sched_clock_stable() using hotplug. This exposed a fundamental problem with the interface, we should never mark the TSC stable if we ever find it to be unstable. Therefore set_sched_clock_stable() is a broken interface. The reason it existed is that not having it is a pain, it means all relevant architecture code needs to call clear_sched_clock_stable() where appropriate. Of the three architectures that select HAVE_UNSTABLE_SCHED_CLOCK ia64 and parisc are trivial in that they never called set_sched_clock_stable(), so add an unconditional call to clear_sched_clock_stable() to them. For x86 the story is a lot more involved, and what this patch tries to do is ensure we preserve the status quo. So even is Cyrix or Transmeta have usable TSC they never called set_sched_clock_stable() so they now get an explicit mark unstable. Reported-by: Mike Galbraith Signed-off-by: Peter Zijlstra (Intel) Cc: Borislav Petkov Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Fixes: 9881b024b7d7 ("sched/clock: Delay switching sched_clock to stable") Link: http://lkml.kernel.org/r/20170119133633.GB6536@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar --- include/linux/sched.h | 1 - 1 file changed, 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/sched.h b/include/linux/sched.h index a8daed914eef..69e6852fede1 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2547,7 +2547,6 @@ extern void sched_clock_init_late(void); * is reliable after all: */ extern int sched_clock_stable(void); -extern void set_sched_clock_stable(void); extern void clear_sched_clock_stable(void); extern void sched_clock_tick(void); -- cgit v1.3-18-gd494