[PATCH v5 1/4] printk/nmi: generic solution for safe printk in NMI

[Sergey Senozhatsky]

On (04/20/17 15:11), Petr Mladek wrote:
[..]
>  void printk_nmi_enter(void)
>  {
> -	this_cpu_or(printk_context, PRINTK_NMI_CONTEXT_MASK);
> +	/*
> +	 * The size of the extra per-CPU buffer is limited. Use it
> +	 * only when really needed.
> +	 */
> +	if (this_cpu_read(printk_context) & PRINTK_SAFE_CONTEXT_MASK ||
> +	    raw_spin_is_locked(&logbuf_lock)) {

can we please have && here?


[..]
> diff --git a/lib/nmi_backtrace.c b/lib/nmi_backtrace.c
> index 4e8a30d1c22f..0bc0a3535a8a 100644
> --- a/lib/nmi_backtrace.c
> +++ b/lib/nmi_backtrace.c
> @@ -86,9 +86,11 @@ void nmi_trigger_cpumask_backtrace(const cpumask_t *mask,
>  
>  bool nmi_cpu_backtrace(struct pt_regs *regs)
>  {
> +	static arch_spinlock_t lock = __ARCH_SPIN_LOCK_UNLOCKED;
>  	int cpu = smp_processor_id();
>  
>  	if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
> +		arch_spin_lock(&lock);
>  		if (regs && cpu_in_idle(instruction_pointer(regs))) {
>  			pr_warn("NMI backtrace for cpu %d skipped: idling at pc %#lx\n",
>  				cpu, instruction_pointer(regs));
> @@ -99,6 +101,7 @@ bool nmi_cpu_backtrace(struct pt_regs *regs)
>  			else
>  				dump_stack();
>  		}
> +		arch_spin_unlock(&lock);
>  		cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
>  		return true;
>  	}

can the nmi_backtrace part be a patch on its own?

	-ss