On Mon, Oct 22, 2012 at 10:01 AM, Eric Dumazet <eric.duma...@gmail.com> wrote:
> This looks like a corruption of s->sequence, and is value is odd, even
> if no writer is alive.
>
> Does local_bh_disable() disables preemption on RT ?
Hmmm....
With PREEMPT_RT_FULL defined (as we have):
void local_bh_disable(void)
{
migrate_disable();
current->softirq_nestcnt++;
}
And the RT patches add the following:
#ifdef CONFIG_PREEMPT_RT_FULL
# define preempt_disable_rt() preempt_disable()
# define preempt_enable_rt() preempt_enable()
# define preempt_disable_nort() do { } while (0)
# define preempt_enable_nort() do { } while (0)
# ifdef CONFIG_SMP
extern void migrate_disable(void);
extern void migrate_enable(void);
# else /* CONFIG_SMP */
# define migrate_disable() do { } while (0)
# define migrate_enable() do { } while (0)
# endif /* CONFIG_SMP */
#else
# define preempt_disable_rt() do { } while (0)
# define preempt_enable_rt() do { } while (0)
# define preempt_disable_nort() preempt_disable()
# define preempt_enable_nort() preempt_enable()
# define migrate_disable() preempt_disable()
# define migrate_enable() preempt_enable()
#endif
And since we are not SMP, local_bh_disable() essentially does nothing.
These definitions are consistent across all the RT patches, up to
3.6.2-rt4 (as far as I can tell).
Now, is preemption required to be disabled in non-SMP systems?
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