[Crash-utility] Re: [ANNOUNCE][RFC][PATCH] Crash-utility, tracing: enable crash to analyze tracing from core-file (make tracing can act as a flight recorder)

[Lai Jiangshan]

Dave Anderson wrote:
> Hello Lai,
> 
> If ever there was a perfect candidate for a crash utility extension module,
> this is it.  This functionality is far too subsystem-specific to included as
> a generic command.  There has not been a "new" base crash command in many years.
> 
> Reviewing the patch, the "trace" command can easily be created as an extension
> module.  The only things that need to be done are:

Your suggest is very helpful. We accept it. We're doing it now.
Thank you very much.


>   
>   (2) Put the "int nr_cpu_ids" variable into the ftrace.c extension
>       module, where you still will have access to the global "kt" 
>       kernel_table pointer. 
>

There is a bug in my box: crash can not recognize the real cpus number,
kt->cpus is wrong. So I fix it and put nr_cpu_ids in the kernel_table.
I'll sent a separate patch for it soon.

In current linux kernel, nr_cpu_ids is recommended to be used instead
of old NR_CPUS. Because CONFIG_NR_CPUS=4096, it's too big for a lot of systems.

kmalloc(sizeof(struct foo) * NR_CPUS) ==> kmalloc(sizeof(struct foo) * nr_cpu_ids)
for (i=0; i < NR_CPUS; i++) ==> for (i=0; i < nr_cpu_ids; i++)

NR_CPUS is also 4096 in crash now, so I also suggest using nr_cpu_ids
instead of NR_CPUS in crash's code when the symbol "nr_cpu_ids" exists.

Lai.