On 05/21/12 13:10, Venkat Subbiah wrote:
> On 05/16/2012 06:09 PM, Frank Rowand wrote:
>> Updates console-make-rt-friendly.patch
>>
>> #ifdef CONFIG_PREEMPT_RT_FULL, printk() output is never flushed by
>> printk() because:
> So this is an issue for printk() itself and is not just for early_printk()?
>
>
> # 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()
>
> As I read it console_trylock_for_printk() is called from printk() but in
> code it is called from vprintk()
Yes, I goofed on the indentation, starting at console_trylock_for_printk().
It should have been:
# 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
Thanks,
Frank
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