Alan Stern wrote:
> On Tue, 3 Jul 2007, Steven Rostedt wrote:
>
> You never answered my second question. Is this sort of thing
> acceptable?
Doh! I never noticed your second question. Sorry about that.
>
> DECLARE_SPINLOCK(lock);
>
> static void irq_handler()
> {
> spin_lock_irqsave(&lock, flags);
> ...
> internal_func();
> ...
> spin_lock_irqrestore(&lock, flags);
> }
>
> static void internal_func()
> {
> ...
> spin_unlock(&lock);
> invoke_callback();
> spin_lock(&lock);
> ...
> }
Perfectly fine! No problems, we do it too.
>
> For that matter, would it be okay to use spin_lock_irq() rather than
> spin_lock_irqsave() in the IRQ handler? Assume the handler was
> registered without IRQF_DISABLED.
If it works on vanilla, it should work with RT. That is, if you use all
the spin_lock variants. In RT, spin_lock(), spin_lock_irqsave(), and
spin_lock_irq() are simply all the same. No difference.
from -rt patch include/linux/spinlock.h:
#ifdef CONFIG_PREEMPT_RT
# define _spin_lock(l) rt_spin_lock(l)
# define _spin_lock_nested(l, s) rt_spin_lock_nested(l, s)
# define _spin_lock_bh(l) rt_spin_lock(l)
# define _spin_lock_irq(l) rt_spin_lock(l)
# define _spin_unlock(l) rt_spin_unlock(l)
# define _spin_unlock_no_resched(l) rt_spin_unlock(l)
# define _spin_unlock_bh(l) rt_spin_unlock(l)
# define _spin_unlock_irq(l) rt_spin_unlock(l)
# define _spin_unlock_irqrestore(l, f) rt_spin_unlock(l)
static inline unsigned long __lockfunc _spin_lock_irqsave(spinlock_t *lock)
{
rt_spin_lock(lock);
return 0;
}
static inline unsigned long __lockfunc
_spin_lock_irqsave_nested(spinlock_t *lock, int subclass)
{
rt_spin_lock_nested(lock, subclass);
return 0;
}
#else
The nesting is for lockdep.
:-)
-- Steve
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