Messages in this thread | | | Date | Thu, 4 Jul 2013 11:57:39 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH 1/3] clocksource: clean up clocksource_select |
| |
On Thu, 4 Jul 2013, Alex Shi wrote:
> After clocksource_find_best() introduced, it is impossible to get into > some code path. so clean them up.
That's wrong.
> Signed-off-by: Alex Shi <alex.shi@intel.com> > --- > kernel/time/clocksource.c | 16 +--------------- > 1 file changed, 1 insertion(+), 15 deletions(-) > > diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c > index e713ef7..021c159 100644 > --- a/kernel/time/clocksource.c > +++ b/kernel/time/clocksource.c > @@ -582,26 +582,12 @@ static void __clocksource_select(bool skipcur) > if (!best) > return; > > - /* Check for the override clocksource. */ > list_for_each_entry(cs, &clocksource_list, list) { > if (skipcur && cs == curr_clocksource) > continue; > if (strcmp(cs->name, override_name) != 0) > continue;
We need this check and it is completely unrelated to the problem you're trying to solve.
Assume the following:
System boots with clocksource A and switches into highres mode. Now clocksource B gets registered and B is not highres capable.
clocksource_find_best() selects again A, but we have clocksource=B on the kernel command line to override the kernel decision.
By removing the check, you install he non highres capable clocksource B and kill the machine.
> - /* > - * Check to make sure we don't switch to a non-highres > - * capable clocksource if the tick code is in oneshot > - * mode (highres or nohz) > - */ > - if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) && oneshot) { > - /* Override clocksource cannot be used. */ > - printk(KERN_WARNING "Override clocksource %s is not " > - "HRT compatible. Cannot switch while in " > - "HRT/NOHZ mode\n", cs->name); > - override_name[0] = 0; > - } else > - /* Override clocksource can be used. */ > - best = cs; > + best = cs; > break; > }
Thanks,
tglx
| |