On Thu, 2007-03-08 at 08:01 -0500, linux-os (Dick Johnson) wrote:
> > Anything kernel configuration I need to be aware of to enable
> > preemption in kernel?
> >
> >
> > Thank you,
> > LNgo
> >
>
> First, in the ioctl, if you need spin-locks, you need to use
> spin_lock_irqsave/spin_unlock/irqrestore. The ones that don't
> save and restore are for the ISR where we know that the interrupts
> are already off and don't intend to turn them on. Further, make
As usual completely wrong:
ioctl code is called with interrupts enabled. So if you need to protect
against interrupts it is completely correct to use spin_lock_irq /
spin_unlock_irq. There is nothing to save and nothing to restore.
> sure that you don't try to schedule() with the interrupts off.
>
> interruptible_sleep_on(&qu);
> ^______ Where is this?
Not included in the pseudo code.
> This must be accessible both in the ISR and in the ioctl(). It
> also needs to have been properly initialized when your module
> was installed (see numerious code samples in the kernel).
Instead of blurbing about obvious things you should point Luong to the
real problems:
include/linux/wait.h:
/*
* These are the old interfaces to sleep waiting for an event.
* They are racy. DO NOT use them, use the wait_event* interfaces above.
* We plan to remove these interfaces during 2.7.
*/
extern void FASTCALL(sleep_on(wait_queue_head_t *q));
extern long FASTCALL(sleep_on_timeout(wait_queue_head_t *q,
signed long timeout));
extern void FASTCALL(interruptible_sleep_on(wait_queue_head_t *q));
extern long FASTCALL(interruptible_sleep_on_timeout(wait_queue_head_t *q,
signed long timeout));
Luong, please use wait_event_interruptible() instead.
spin_lock_irq(dev->lock);
do_whatever_you_need_to_initialize(dev);
dev->event_happened = 0;
spin_unlock_irq(dev->lock);
res = wait_event_interruptible(&dev->queue, dev->event_happened != 0);
Thanks,
tglx
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