Re: [PATCH v3 1/7] arm64: ftrace: adjust callsite addresses examined by stack tracer

[AKASHI Takahiro]

On 10/14/2015 12:37 AM, Steven Rostedt wrote:
> On Thu,  8 Oct 2015 19:01:38 +0900
> AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx> wrote:
>
> >   extern int stack_tracer_enabled;
> >   int
> >   stack_trace_sysctl(struct ctl_table *table, int write,
> > diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
> > index b746399..30521ea 100644
> > --- a/kernel/trace/trace_stack.c
> > +++ b/kernel/trace/trace_stack.c
> > @@ -105,7 +105,7 @@ check_stack(unsigned long ip, unsigned long *stack)
> >
> >   	/* Skip over the overhead of the stack tracer itself */
> >   	for (i = 0; i < max_stack_trace.nr_entries; i++) {
> > -		if (stack_dump_trace[i] == ip)
> > +		if ((stack_dump_trace[i] + FTRACE_STACK_FRAME_OFFSET) == ip)
> >   			break;
> >   	}
> >
> > @@ -133,7 +133,8 @@ check_stack(unsigned long ip, unsigned long *stack)
> >   		for (; p < top && i < max_stack_trace.nr_entries; p++) {
> >   			if (stack_dump_trace[i] == ULONG_MAX)
> >   				break;
> > -			if (*p == stack_dump_trace[i]) {
> > +			if (*p == (stack_dump_trace[i]
> > +					+ FTRACE_STACK_FRAME_OFFSET)) {
>
> I'm fine with the patch, but this is one of those cases that I think
> the 80 column max limit produces uglier code than just going a little
> over.
>
> Or, we can add a helper variable in both locations:
>
> 	addr = stack_dump_trace[i] + FTRACE_STACK_FRAME_OFFSET;
> 	if (*p == addr) {
>
> gcc should be smart enough to optimize out the addr variable.

Thanks, I will take this.
(please note that this patch won't be necessary if my patch5,6 and 7 are
accepted.)

-Takahiro AKASHI

> -- Steve
>
> >   				stack_dump_trace[x] = stack_dump_trace[i++];
> >   				this_size = stack_dump_index[x++] =
> >   					(top - p) * sizeof(unsigned long);
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/