Re: [PATCH 26/50] powerpc: Add show_stack_loglvl()

[Michael Ellerman <mpe@ellerman.id.au>]

Dmitry Safonov <dima@arista.com> writes:
> Currently, the log-level of show_stack() depends on a platform
> realization. It creates situations where the headers are printed with
> lower log level or higher than the stacktrace (depending on
> a platform or user).

Yes, I've had bug reports where the stacktrace is missing, which is
annoying. Thanks for trying to fix the problem.

> Furthermore, it forces the logic decision from user to an architecture
> side. In result, some users as sysrq/kdb/etc are doing tricks with
> temporary rising console_loglevel while printing their messages.
> And in result it not only may print unwanted messages from other CPUs,
> but also omit printing at all in the unlucky case where the printk()
> was deferred.
>
> Introducing log-level parameter and KERN_UNSUPPRESSED [1] seems
> an easier approach than introducing more printk buffers.
> Also, it will consolidate printings with headers.
>
> Introduce show_stack_loglvl(), that eventually will substitute
> show_stack().
>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: linuxppc-dev@lists.ozlabs.org
> [1]: https://lore.kernel.org/lkml/20190528002412.1625-1-dima@arista.com/T/#u
> Signed-off-by: Dmitry Safonov <dima@arista.com>
> ---
>  arch/powerpc/kernel/process.c | 18 +++++++++++++-----
>  1 file changed, 13 insertions(+), 5 deletions(-)

This looks good to me.

Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)

cheers


> diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> index 639ceae7da9d..34b46680a196 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -2028,7 +2028,8 @@ unsigned long get_wchan(struct task_struct *p)
>  
>  static int kstack_depth_to_print = CONFIG_PRINT_STACK_DEPTH;
>  
> -void show_stack(struct task_struct *tsk, unsigned long *stack)
> +void show_stack_loglvl(struct task_struct *tsk, unsigned long *stack,
> +		       const char *loglvl)
>  {
>  	unsigned long sp, ip, lr, newsp;
>  	int count = 0;
> @@ -2053,7 +2054,7 @@ void show_stack(struct task_struct *tsk, unsigned long *stack)
>  	}
>  
>  	lr = 0;
> -	printk("Call Trace:\n");
> +	printk("%sCall Trace:\n", loglvl);
>  	do {
>  		if (!validate_sp(sp, tsk, STACK_FRAME_OVERHEAD))
>  			break;
> @@ -2062,7 +2063,8 @@ void show_stack(struct task_struct *tsk, unsigned long *stack)
>  		newsp = stack[0];
>  		ip = stack[STACK_FRAME_LR_SAVE];
>  		if (!firstframe || ip != lr) {
> -			printk("["REG"] ["REG"] %pS", sp, ip, (void *)ip);
> +			printk("%s["REG"] ["REG"] %pS",
> +				loglvl, sp, ip, (void *)ip);
>  #ifdef CONFIG_FUNCTION_GRAPH_TRACER
>  			ret_addr = ftrace_graph_ret_addr(current,
>  						&ftrace_idx, ip, stack);
> @@ -2084,8 +2086,9 @@ void show_stack(struct task_struct *tsk, unsigned long *stack)
>  			struct pt_regs *regs = (struct pt_regs *)
>  				(sp + STACK_FRAME_OVERHEAD);
>  			lr = regs->link;
> -			printk("--- interrupt: %lx at %pS\n    LR = %pS\n",
> -			       regs->trap, (void *)regs->nip, (void *)lr);
> +			printk("%s--- interrupt: %lx at %pS\n    LR = %pS\n",
> +			       loglvl, regs->trap,
> +			       (void *)regs->nip, (void *)lr);
>  			firstframe = 1;
>  		}
>  
> @@ -2095,6 +2098,11 @@ void show_stack(struct task_struct *tsk, unsigned long *stack)
>  	put_task_stack(tsk);
>  }
>  
> +void show_stack(struct task_struct *tsk, unsigned long *stack)
> +{
> +	show_stack_loglvl(tsk, stack, KERN_DEFAULT);
> +}
> +
>  #ifdef CONFIG_PPC64
>  /* Called with hard IRQs off */
>  void notrace __ppc64_runlatch_on(void)
> -- 
> 2.23.0