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>
Cc: Frank <Frank_Rowand@xxxxxxxxxxx>
Link: http://lkml.kernel.org/r/4FB44FD0.4090800@xxxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
kernel/printk.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/printk.c b/kernel/printk.c
index 9eabbbb..66e83e5 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -836,7 +836,7 @@ static int console_trylock_for_printk(unsigned int cpu, unsigned long flags)
int retval = 0, wake = 0;
#ifdef CONFIG_PREEMPT_RT_FULL
int lock = (!early_boot_irqs_disabled && !irqs_disabled_flags(flags) &&
- !preempt_count()) || sysrq_in_progress;
+ (preempt_count() <= 1)) || sysrq_in_progress;
#else
int lock = 1;
#endif
--
1.7.10.4
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