Messages in this thread | | | Subject | Re: [PATCH] printk: robustify printk | From | Peter Zijlstra <> | Date | Fri, 08 Aug 2008 21:21:08 +0200 |
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On Fri, 2008-08-08 at 12:14 -0700, Andrew Morton wrote: > On Fri, 08 Aug 2008 20:14:28 +0200 > Peter Zijlstra <a.p.zijlstra@chello.nl> wrote: > > > void wake_up_klogd(void) > > { > > - if (!oops_in_progress && waitqueue_active(&log_wait)) > > - wake_up_interruptible(&log_wait); > > + unsigned long flags; > > + struct klogd_wakeup_state *kws; > > + > > + if (!waitqueue_active(&log_wait)) > > + return; > > + > > + local_irq_save(flags); > > + kws = &__get_cpu_var(kws); > > + if (!kws->pending) { > > + kws->pending = 1; > > + call_rcu(&kws->head, __wake_up_klogd); > > + } > > + local_irq_restore(flags); > > } > > Note that kernel/rcupreempt.c's flavour of call_rcu() takes > RCU_DATA_ME().lock, so there are still code sites from which a printk > can deadlock. Only now, it is config-dependent. > > From a quick look it appears that large amounts of kernel/rcupreempt.c > are now a printk-free zone.
Drad, missed that bit, I did look at the calling end, but forgot the call_rcu() end :-/
The initial printk_tick() based implementation didn't suffer this problem, should we revert to that scheme?
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