Re: [PATCH v5 0/2] printk: Console owner and waiter logic cleanup

Sergey Senozhatsky
2018-01-18T05:42:59Z

On (01/17/18 12:12), Steven Rostedt wrote:
[..]
> /*
> * Can we actually use the console at this time on this cpu?
> @@ -2333,6 +2390,7 @@ void console_unlock(void)
>
> for (;;) {
> struct printk_log *msg;
> + bool offload;
> size_t ext_len = 0;
> size_t len;
>
> @@ -2393,15 +2451,20 @@ void console_unlock(void)
> * waiter waiting to take over.
> */
> console_lock_spinning_enable();
> + offload = recursion_check_start();
>
> stop_critical_timings(); /* don't trace print latency */
> call_console_drivers(ext_text, ext_len, text, len);
> start_critical_timings();
>
> + recursion_check_finish(offload);
> +
> if (console_lock_spinning_disable_and_check()) {
> printk_safe_exit_irqrestore(flags);
> return;
> }
> + if (offload)
> + kick_offload_thread();
>
> printk_safe_exit_irqrestore(flags);
^^^^^^^^^^^^^^^^

but we call console drivers in printk_safe.
printk -> console_drivers -> printk will be
redirected to this-CPU printk_safe buffer.

-ss