Re: [PATCH 7/7] arch: Fix STACKTRACE_SUPPORT

Guo Ren
2021-10-09T09:36:55Z

Thx Peter,

On Fri, Oct 8, 2021 at 7:18 PM Peter Zijlstra <peterz@infradead.org> wrote:
>
> A few archs got save_stack_trace_tsk() vs in_sched_functions() wrong.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> ---
> arch/csky/kernel/stacktrace.c | 7 ++++++-
> arch/mips/kernel/stacktrace.c | 27 ++++++++++++++++-----------
> arch/nds32/kernel/stacktrace.c | 21 +++++++++++----------
> 3 files changed, 33 insertions(+), 22 deletions(-)
>
> --- a/arch/csky/kernel/stacktrace.c
> +++ b/arch/csky/kernel/stacktrace.c
> @@ -122,12 +122,17 @@ static bool save_trace(unsigned long pc,
> return __save_trace(pc, arg, false);
> }
>
> +static bool save_trace_nosched(unsigned long pc, void *arg)
> +{
> + return __save_trace(pc, arg, true);
> +}
> +
> /*
> * Save stack-backtrace addresses into a stack_trace buffer.
> */
> void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
> {
> - walk_stackframe(tsk, NULL, save_trace, trace);
> + walk_stackframe(tsk, NULL, save_trace_nosched, trace);
> }
> EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
I think the patch should be:
@@ -138,7 +138,7 @@ static bool __save_trace(unsigned long pc, void
*arg, bool nosched)

static bool save_trace(unsigned long pc, void *arg)
{
- return __save_trace(pc, arg, false);
+ return __save_trace(pc, arg, true);
}

Another question:
If we put sched_text in the backtrace buffer, just cause put no useful
information in wchan, right?
(I think it wouldn't cause a worse problem than debugging.)

>
> --- a/arch/mips/kernel/stacktrace.c
> +++ b/arch/mips/kernel/stacktrace.c
> @@ -66,16 +66,7 @@ static void save_context_stack(struct st
> #endif
> }
>
> -/*
> - * Save stack-backtrace addresses into a stack_trace buffer.
> - */
> -void save_stack_trace(struct stack_trace *trace)
> -{
> - save_stack_trace_tsk(current, trace);
> -}
> -EXPORT_SYMBOL_GPL(save_stack_trace);
> -
> -void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
> +static void __save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace, bool savesched)
> {
> struct pt_regs dummyregs;
> struct pt_regs *regs = &dummyregs;
> @@ -88,6 +79,20 @@ void save_stack_trace_tsk(struct task_st
> regs->cp0_epc = tsk->thread.reg31;
> } else
> prepare_frametrace(regs);
> - save_context_stack(trace, tsk, regs, tsk == current);
> + save_context_stack(trace, tsk, regs, savesched);
> +}
> +
> +/*
> + * Save stack-backtrace addresses into a stack_trace buffer.
> + */
> +void save_stack_trace(struct stack_trace *trace)
> +{
> + __save_stack_trace_tsk(current, trace, true);
> +}
> +EXPORT_SYMBOL_GPL(save_stack_trace);
> +
> +void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
> +{
> + __save_stack_trace_tsk(tsk, trace, false);
> }
> EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
> --- a/arch/nds32/kernel/stacktrace.c
> +++ b/arch/nds32/kernel/stacktrace.c
> @@ -6,25 +6,16 @@
> #include <linux/stacktrace.h>
> #include <linux/ftrace.h>
>
> -void save_stack_trace(struct stack_trace *trace)
> -{
> - save_stack_trace_tsk(current, trace);
> -}
> -EXPORT_SYMBOL_GPL(save_stack_trace);
> -
> -void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
> +static void __save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace, bool savesched)
> {
> unsigned long *fpn;
> int skip = trace->skip;
> - int savesched;
> int graph_idx = 0;
>
> if (tsk == current) {
> __asm__ __volatile__("\tori\t%0, $fp, #0\n":"=r"(fpn));
> - savesched = 1;
> } else {
> fpn = (unsigned long *)thread_saved_fp(tsk);
> - savesched = 0;
> }
>
> while (!kstack_end(fpn) && !((unsigned long)fpn & 0x3)
> @@ -50,4 +41,14 @@ void save_stack_trace_tsk(struct task_st
> fpn = (unsigned long *)fpp;
> }
> }
> +void save_stack_trace(struct stack_trace *trace)
> +{
> + __save_stack_trace_tsk(current, trace, true);
> +}
> +EXPORT_SYMBOL_GPL(save_stack_trace);
> +
> +void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
> +{
> + __save_stack_trace_tsk(tsk, trace, false);
> +}
> EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
>
>

--
Best Regards
Guo Ren

ML: https://lore.kernel.org/linux-csky/