From 1afe526f5d795b8b800d2c307019ab4807970050 Mon Sep 17 00:00:00 2001 From: Frank Rowand Date: Wed, 16 May 2012 18:09:36 -0700 Subject: fix printk flush of messages 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 Cc: Frank Link: http://lkml.kernel.org/r/4FB44FD0.4090800@am.sony.com Signed-off-by: Thomas Gleixner --- kernel/printk.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/printk.c b/kernel/printk.c index 60f4290d796b..f2c459f43d25 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -835,7 +835,7 @@ static int console_trylock_for_printk(unsigned int cpu, unsigned long flags) { #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 -- cgit v1.2.3