Messages in this thread | | | Subject | Re: 'global' rq->clock | From | Benjamin Herrenschmidt <> | Date | Sun, 04 May 2008 12:22:47 +1000 |
| |
> on nohz we still keep jiffies uptodate - despite there not being an > explicit 'keep jiffies uptodate' tick interrupt anymore. So on every > irq_enter() we roll jiffies forward - if needed - and thus emulate > jiffies behavior to drivers and core kernel code, etc. > > if an IPI on Power does not do an irq_enter() then you might miss out on > updated jiffies. That might not matter for most jiffies, but you might > also miss out on the 'touch the softlockup watchdog because we just woke > from idle' action. This is what triggered the false positive warnings on > Sparc64. > > the same bug existed on x86 too: that too does a few IPIs without > irq_enter/irq_exit. We now removed the softlockup dependency so it > should not be required to do an irq_enter()/exit anymore - unless the > code that the IPI uses accesses jiffies. (but that would be unusual)
Allright, so it looks like we don't have a problem today, though I'll be careful if some of our CPUs come up with more fancy ways to do IPIs. Currently they are just normal interrupts, so we do irq_enter/exit and we process softirqs on the way out.
Ben.
| |