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SubjectRe: [PATCH -mm] extend sysrq-p functionality to cover all CPUs
Andrew Morton wrote:

>On Sun, 9 Mar 2008 22:14:58 -0400 Rik van Riel <riel@surriel.com> wrote:
>
>
>
>>SysRP-P is not all that useful on SMP systems, since the sysrq
>>irq rarely ends up on the CPU that we actually want to investigate.
>>
>>This patch extends sysrq-p to print a backtrace for every CPU,
>>not just the lucky one that gets the sysrq irq. With this patch,
>>"echo p > /proc/sysrq-trigger" does something useful.
>>
>>Signed-off-by: Rik van Riel <riel@redhat.com>
>>
>>diff -up linux-2.6.25-rc3-mm1/drivers/char/sysrq.c.multicpu linux-2.6.25-rc3-mm1/drivers/char/sysrq.c
>>--- linux-2.6.25-rc3-mm1/drivers/char/sysrq.c.multicpu 2008-03-09 20:22:17.000000000 -0400
>>+++ linux-2.6.25-rc3-mm1/drivers/char/sysrq.c 2008-03-09 21:54:02.000000000 -0400
>>@@ -196,11 +196,29 @@ static struct sysrq_key_op sysrq_showloc
>> #define sysrq_showlocks_op (*(struct sysrq_key_op *)0)
>> #endif
>>
>>+static DEFINE_SPINLOCK(show_lock);
>>+static void showacpu(void *dummy)
>>+{
>>+ struct pt_regs *regs = get_irq_regs();
>>+
>>+ spin_lock(&show_lock);
>>+ printk("CPU%d:\n", smp_processor_id());
>>+ show_stack(NULL, NULL);
>>+ spin_unlock(&show_lock);
>>+}
>>+static void sysrq_showregs_othercpus(struct work_struct *dummy)
>>+{
>>+ smp_call_function(showacpu, NULL, 0, 0);
>>+}
>>+static DECLARE_WORK(sysrq_showregs, sysrq_showregs_othercpus);
>> static void sysrq_handle_showregs(int key, struct tty_struct *tty)
>> {
>> struct pt_regs *regs = get_irq_regs();
>>- if (regs)
>>+ if (regs) {
>>+ printk("CPU%d:\n", smp_processor_id());
>> show_regs(regs);
>>+ }
>>+ schedule_work(&sysrq_showregs);
>> }
>> static struct sysrq_key_op sysrq_showregs_op = {
>> .handler = sysrq_handle_showregs,
>>
>>
>
>Doesn't everyone have a copy of this somewhere? ;)
>

Yes, but we use W instead of P. Dont you want to keep the old AlsSysrq
P and add
a new SPM version using a defferent letter ?

Larry

>
>However it does have the downside that info can scroll away on large cpu
>counts. Maybe it should be a new sysrq command?
>
>
>




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