Hello Alexander, On Sat, Jul 18, 2015 at 11:23 AM, Alexander <alexhoppus111@gmail.com> wrote:
Hi! When i checked how kernel printing works, i mentioned that it takes messages from log_buffer in console_unlock and gives it to call_console_drivers -> ... -> some uart bsp function. Basically, as i see this BSP realization tries to flush all message chars in busyloop ... so it waits until FIFO_NOT_FULL bit will be dropped by UART and it will be able to push the next byte. Basically, as i see userspace printing do something different. It puts N_FIFO_BYTES and exits, next, when FIFO will be freed - interrupt will be generated, and other characters will be put into UART FIFO. Can we do something similar for kernel printing? i.e. do not busyloop sending char after char, but put N_FIFO chars and flush other in interrupt. When panic will occur we can do busyloop printing again. Is it reliable? Suppose we have several cores. Thank you.
What about trying this patch, https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/kerne... Its not changing console printing through UART to interrupt mode. But minimizes the time interrupts being disabled on printk(). Thanks, Arun
-- Alexander <alexhoppus111@gmail.com>
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