On Tue, Jun 23, 2020 at 6:30 PM Dmitry Safonov <[email protected]> wrote:
> show_trace_log_lvl() provides x86 platform-specific way to unwind
> backtrace with a given log level. Unfortunately, registers dump(s) are
> not printed with the same log level - instead, KERN_DEFAULT is always
> used.
>
> Arista's switches uses quite common setup with rsyslog, where only
> urgent messages goes to console (console_log_level=KERN_ERR), everything
> else goes into /var/log/ as the console baud-rate often is indecently
> slow (9600 bps).
>
> Backtrace dumps without registers printed have proven to be as useful as
> morning standups. Furthermore, in order to introduce KERN_UNSUPPRESSED
> (which I believe is still the most elegant way to fix raciness of sysrq[1])
> the log level should be passed down the stack to register dumping
> functions. Besides, I have a potential use-case for printing traces
> with KERN_DEBUG level [2] (where registers dump shouldn't appear with
> higher log level).
>
> Add log_lvl parameter to __show_regs().
> Keep the used log level intact to separate visible change.
This change seems like a good idea to me; just one small nit:
[...]
> void show_regs(struct pt_regs *regs)
> {
> + int print_kernel_regs;
> +
> show_regs_print_info(KERN_DEFAULT);
>
> - __show_regs(regs, user_mode(regs) ? SHOW_REGS_USER : SHOW_REGS_ALL);
> + print_kernel_regs = user_mode(regs) ? SHOW_REGS_USER : SHOW_REGS_ALL;
> + __show_regs(regs, print_kernel_regs, KERN_DEFAULT);
print_kernel_regs should probably have type "enum show_regs_mode"?
