[PATCH v8 1/4] nmi_backtrace: add more trigger_*_cpu_backtrace() methods

On Fri 2016-08-19 21:54:31, Chris Metcalf wrote:

On 8/18/2016 10:12 AM, Petr Mladek wrote:

quoted

On Tue 2016-08-16 15:50:21, Chris Metcalf wrote:

quoted

Currently you can only request a backtrace of either all cpus, or
all cpus but yourself.  It can also be helpful to request a remote
backtrace of a single cpu, and since we want that, the logical
extension is to support a cpumask as the underlying primitive.

This change modifies the existing lib/nmi_backtrace.c code to take
a cpumask as its basic primitive, and modifies the linux/nmi.h code
to use the new "cpumask" method instead.

The mips code ignored the "include_self" boolean but with this change
it will now also dump a local backtrace if requested.

diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index 7429ad09fbe3..fea1fa7726e3 100644
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c

@@ -569,9 +569,16 @@ static void arch_dump_stack(void *info)
 	dump_stack();
 }
-void arch_trigger_all_cpu_backtrace(bool include_self)
+void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
 {
-	smp_call_function(arch_dump_stack, NULL, 1);
+	long this_cpu = get_cpu();
+
+	if (cpumask_test_cpu(this_cpu, mask) && !exclude_self)
+		dump_stack();

The bit is not cleared in the mask. Therefore arch_dump_stack
will get called for this CPU as well.

Actually, and kind of confusingly, smp_call_function_many() never calls
the current cpu, even if it is in the mask.  So this code is OK as-is.

I see it now.

quoted

Otherwise the patch patch looks good to me.

Great, thanks!  Should I add your Reviewed-by?

Yup. This patch looks fine then:

Reviewed-by: Petr Mladek <pmladek@suse.com>

Best Regards,
Petr