On Tue, May 18, 2010 at 8:13 AM, Xianghua Xiao <xiaoxianghua@xxxxxxxxx> wrote: > I would like to have printk output to my ttyS0 console all the time, > with 2.6.33-rt17, after kernel is booted up with all messages shown > normally on the serial port until I login in, from this point on, all > printk messages go to 'dmesg(log_buf)' fine, but I could never get > them shown up on serial console anymore. I tried adjust > /proc/sys/kernel/printk etc none helped. > > Switch PREEMPT_RT to PREEMPT_VOLUNTARY and reboot, now everything > works, i.e. I can see printk on my console after I login. > > Look at the RT patch itself, I do find some changes to printk itself, > however I'm unsure what is causing this(i.e printk not going to > console after login). > > Thanks, > Xianghua > Thomas, I could not get dmesg output to console/serial and klogd(/var/log/messages) anymore with 2.6.33-rt17 _after_ the kernel boot is done(on non-RT kernel it works fine). I made below changes it starts to work again, however I'm unsure how safe the change is. Please advise. During googling I found this: http://lkml.org/lkml/2008/1/24/390, fyi. Thanks a lot! Xianghua diff --git a/kernel/printk.c b/kernel/printk.c index 073d27f..48ef843 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -430,7 +430,6 @@ static void __call_console_drivers(unsigned start, unsigned end) for_each_console(con) { if ((con->flags & CON_ENABLED) && con->write && - console_atomic_safe(con) && (cpu_online(raw_smp_processor_id()) || (con->flags & CON_ANYTIME))) { set_printk_might_sleep(1); @@ -1093,9 +1092,6 @@ void release_console_mutex(void) * printk from non-preemptible sections so this is for the emergency * case only. */ -#ifdef CONFIG_PREEMPT_RT - if (!in_atomic() && !irqs_disabled()) -#endif if (wake_klogd) wake_up_klogd(); } -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
