Commit 3c2047cd authored by Rusty Russell's avatar Rusty Russell Committed by Ingo Molnar
Browse files

x86: if we cannot calibrate the TSC, we panic. 



The current tsc_init() clears the TSC feature bit if the TSC khz
cannot be calculated, causing us to panic in
arch/x86/kernel/cpu/bugs.c check_config().  We should simply mark it
unstable.

Frankly, someone should take an axe to this code.  mark_tsc_unstable()
not only marks it unstable, but sets tsc_enabled to 0, which seems
redundant but is actually important here because means it won't be
used by sched_clock() either.  Perhaps a tristate enum "UNUSABLE,
UNSTABLE, OK" would be clearer, and separate mark_tsc_unstable() and
mark_tsc_broken() functions?

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 9fc34113

arch/x86/kernel/tsc_32.c

+5 −8
Original line number Diff line number Diff line
@@ -392,13 +392,15 @@ void __init tsc_init(void) 
	int cpu;



	if (!cpu_has_tsc)

		goto out_no_tsc;

		return;



	cpu_khz = calculate_cpu_khz();

	tsc_khz = cpu_khz;



	if (!cpu_khz)

		goto out_no_tsc;

	if (!cpu_khz) {

		mark_tsc_unstable("could not calculate TSC khz");

		return;

	}



	printk("Detected %lu.%03lu MHz processor.\n",

				(unsigned long)cpu_khz / 1000,
@@ -431,9 +433,4 @@ void __init tsc_init(void) 
		tsc_enabled = 1;



	clocksource_register(&clocksource_tsc);



	return;



out_no_tsc:

	setup_clear_cpu_cap(X86_FEATURE_TSC);

}