lkml.org 
[lkml]   [2008]   [Mar]   [18]   [last100]   RSS Feed
Views: [more markup]   [less markup]   [headers]   [forward]  
 
Messages in this thread
/
DateTue, 18 Mar 2008 00:14:29 -0700
FromAndrew Morton <>
SubjectRe: use of preempt_count instead of in_atomic() at leds-gpio.c
On Sun, 16 Mar 2008 11:46:23 -0800 David Brownell <david-b@pacbell.net> wrote:

> On Sunday 16 March 2008, Henrique de Moraes Holschuh wrote:
> > Is the use of "if (preempt_count())" to know when to defer led gpio work to
> > a workqueue needed? __Shouldn't "if (in_atomic())" be enough?
> 
> At this point, I don't know of any such reason.
> 
> I remember hunting for the right heuristic, and settling on
> that one for reasons that I can't recall now.  They may even
> be no longer applicable.

Both are incorrect.  When CONFIG_PREEMPT=n we have no support for
determining whether schedule() may be called.  The calling code has to sort
out its stuff on its own.

<greps for preempt_count>

The LEDs code seems to be the sole offender.  print_vma_addr() might be
wrong too, but Ingo did it, and perhaps he knows that all code paths which
call print_vma_addr() from deadlockable contexts have already called
inc_preempt_count().  But is that true for all architectures?

<greps for in_atomic>

omigawd, what have we done, and how can we fix it? :(
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2008-03-18 07:17    [W:0.330 / U:0.280 seconds]
©2003-2008 Jasper Spaans