Attachment 617625 Details for Bug 859226 – fix printk flush of messages

[patch] fix printk flush of messages

fix-printk-flush-of-messages.patch (text/plain), 1.95 KB, created by Luis Claudio R. Goncalves on 2012-09-26 16:05:00 UTC

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Creator: Luis Claudio R. Goncalves

Created: 2012-09-26 16:05:00 UTC

Size: 1.95 KB

patch

obsolete

>commit 172314790a65db61c5f7d7adb91c00f67bcb2166
>Author: Frank Rowand <frank.rowand@am.sony.com>
>Date:   Wed May 16 18:09:36 2012 -0700
>
>    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 <frank.rowand@am.sony.com>
>    Cc: Frank <Frank_Rowand@sonyusa.com>
>    Link: http://lkml.kernel.org/r/4FB44FD0.4090800@am.sony.com
>    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
>
>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

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Attachments on bug 859226: 617625