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Subject[PATCH -mm] extend sysrq-p functionality to cover all CPUs
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,


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