Re: [PATCH] softirq: Fix warnings triggered by netconsole

From: Ingo Molnar
Date: Wed Nov 19 2008 - 04:32:52 EST



* Jarek Poplawski <jarkao2@xxxxxxxxx> 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@xxxxxxx>
> Signed-off-by: Jarek Poplawski <jarkao2@xxxxxxxxx>
> ---
> [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.

printk methods should not be doing softirq processing - period.

Ingo
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