On 05/16/12 18:09, Frank Rowand wrote: > > Updates console-make-rt-friendly.patch > > #ifdef CONFIG_PREEMPT_RT_FULL, printk() output is never flushed by > printk() because: > > # some liberties taken in this pseudo-code to make it easier to follow > printk() > vprintk() > raw_spin_lock(&logbuf_lock) > # increment preempt_count(): > preempt_disable() > result = console_trylock_for_printk() > retval = 0 > # lock will always be false, because preempt_count() will be >= 1 > lock = ... && !preempt_count() > if (lock) > retval = 1 > return retval > # result will always be false since lock will always be false > if (result) > console_unlock() > # this is where the printk() output would be flushed > > > On system boot some printk() output is flushed because register_console() > and tty_open() call console_unlock(). > > > This change also fixes the problem that was previously fixed by > preempt-rt-allow-immediate-magic-sysrq-output-for-preempt_rt_full.patch > > Signed-off-by: Frank Rowand <frank.rowand@xxxxxxxxxxx> > > --- > kernel/printk.c | 2 1 + 1 - 0 ! > 1 file changed, 1 insertion(+), 1 deletion(-) > > Index: b/kernel/printk.c > =================================================================== > --- a/kernel/printk.c > +++ b/kernel/printk.c > @@ -847,7 +847,7 @@ static int console_trylock_for_printk(un > int retval = 0, wake = 0; > #ifdef CONFIG_PREEMPT_RT_FULL > int lock = !early_boot_irqs_disabled && !irqs_disabled_flags(flags) && > - !preempt_count(); > + (preempt_count() <= 1); > #else > int lock = 1; > #endif ... and if patch 1/2 is added to stable, this patch (2/2) is also needed. -Frank -- To unsubscribe from this list: send the line "unsubscribe stable-rt" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
