Re: [Patch 1/2] tracepoints for softirq entry/exit - add softirq-to-name array

Mathieu Desnoyers
2009-03-14T02:53:51Z

* Jason Baron (jbaron@redhat.com) wrote:
>
> create a 'softirq_to_name' array, which is indexed by softirq #, so
> that we can easily convert between the softirq index # and its name, in
> order to get more meaningful output messages.
>
> Signed-off-by: Jason Baron <jbaron@redhat.com>
>
> ---
>
> include/linux/interrupt.h | 5 +++++
> kernel/softirq.c | 9 ++++++++-
> 2 files changed, 13 insertions(+), 1 deletions(-)
>
>
> diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
> index e7bcfd7..da82ee4 100644
> --- a/include/linux/interrupt.h
> +++ b/include/linux/interrupt.h
> @@ -258,6 +258,11 @@ enum
> NR_SOFTIRQS
> };
>
> +/* map softirq index to softirq name. update 'softirq_to_name' in
> + * kernel/softirq.c when adding a new softirq.
> + */
> +extern char *softirq_to_name[NR_SOFTIRQS];
> +
> /* softirq mask and active fields moved to irq_cpustat_t in
> * asm/hardirq.h to get better cache usage. KAO
> */
> diff --git a/kernel/softirq.c b/kernel/softirq.c
> index 40ff3cf..ba1511f 100644
> --- a/kernel/softirq.c
> +++ b/kernel/softirq.c
> @@ -53,6 +53,12 @@ static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp
>
> static DEFINE_PER_CPU(struct task_struct *, ksoftirqd);
>
> +char *softirq_to_name[NR_SOFTIRQS] = {
> + "HI_SOFTIRQ", "TIMER_SOFTIRQ", "NET_TX_SOFTIRQ", "NET_RX_SOFTIRQ",
> + "BLOCK_SOFTIRQ", "TASKLET_SOFTIRQ", "SCHED_SOFTIRQ", "HRTIMER_SOFTIRQ",
> + "RCU_SOFTIRQ"
> +};
> +

Small nit :

this should be a const char *.

Besides that it looks good, and very useful to a tracer. We just have to
make sure this table can eventually be saved into a trace.

Mathieu

> /*
> * we cannot loop indefinitely here to avoid userspace starvation,
> * but we also don't want to introduce a worst case 1/HZ latency
> @@ -209,9 +215,10 @@ restart:
> h->action(h);
>
> if (unlikely(prev_count != preempt_count())) {
> - printk(KERN_ERR "huh, entered softirq %td %p"
> + printk(KERN_ERR "huh, entered softirq %td %s %p"
> "with preempt_count %08x,"
> " exited with %08x?\n", h - softirq_vec,
> + softirq_to_name[h - softirq_vec],
> h->action, prev_count, preempt_count());
> preempt_count() = prev_count;
> }
>

--
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68