Messages in this thread | | | Date | Wed, 19 Nov 2008 11:07:48 +0000 | From | Jarek Poplawski <> | Subject | Re: [PATCH] softirq: Fix warnings triggered by netconsole |
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On Wed, Nov 19, 2008 at 10:32:24AM +0100, Ingo Molnar wrote: > > * Jarek Poplawski <jarkao2@gmail.com> wrote: > > > Consider netconsole case as special in local_bh_enable()/_disable(). > > This patch skips in_irq() and irqs_disabled() warnings for NETPOLL > > configs when it's safe wrt. do_softirq(). > > > > Reported-by: Ferenc Wagner <wferi@niif.hu> > > Signed-off-by: Jarek Poplawski <jarkao2@gmail.com> > > --- > > [apply on top of my first softirq patch in this thread] > > > > diff -Nurp a/kernel/softirq.c b/kernel/softirq.c > > --- a/kernel/softirq.c 2008-11-19 07:33:23.000000000 +0000 > > +++ b/kernel/softirq.c 2008-11-19 07:26:28.000000000 +0000 > > @@ -76,7 +76,12 @@ static void __local_bh_disable(unsigned > > { > > unsigned long flags; > > > > +#ifdef CONFIG_NETPOLL > > + if (!softirq_count()) > > + WARN_ON_ONCE(in_irq()); > > +#else > > WARN_ON_ONCE(in_irq()); > > +#endif > > > > raw_local_irq_save(flags); > > add_preempt_count(SOFTIRQ_OFFSET); > > @@ -138,7 +143,16 @@ static inline void _local_bh_enable_ip(u > > #ifdef CONFIG_TRACE_IRQFLAGS > > unsigned long flags; > > #endif > > +#ifdef CONFIG_NETPOLL > > + /* > > + * Special-case - netconsole runs network code with all interrupts > > + * disabled. Warn only if it can be really dangerous: > > + */ > > + if (softirq_count() == SOFTIRQ_OFFSET) > > + WARN_ON_ONCE(in_irq() || irqs_disabled()); > > +#else > > WARN_ON_ONCE(in_irq() || irqs_disabled()); > > +#endif > > #ifdef CONFIG_TRACE_IRQFLAGS > > local_irq_save(flags); > > #endif > > this is a very ugly patch, not really acceptable.
Well, it's a question of taste. Anyway, this patch is only about warnings, so no big deal. But I still think the first patch reverting local_irq_save() -> local_irq_disable() change should be applied. There is no need to give users any additional lockups risk while we know there are unsolved issues.
BTW, the current situation with: local_irq_disable() in _local_bh_enable() and local_irq_save() in do_softirq() doesn't make much sense. I know, there is local_irq_disable() in __do_softirq() again, but it can be often skipped on this path because of in_interrupt() test (and there is soon this local_irq_restore() in do_softirq()).
Jarek P.
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