Re: Spinlock query

[Rajat Jain]

On 8/30/06, Rik van Riel <riel@xxxxxxxxxxx> wrote:
> Rick Brown wrote:
> > Hi,
> >
> > In my driver (Process context), I have written the following code:
> >
> > --------------------------------------------
> > spin_lock(lock)
> > ...
> > //Critical section to manipulate driver data
>
> ... interrupt hits here
>     interrupt handler tries to grab the spinlock, which is already taken
>     *BOOM*
>
> > spin_u lock(lock)
> > ---------------------------------------------
> >

The interrupt handler TRIES to grab the spinlock, which is already
taken. Why will it "BOOM"? Wouldn't the interrupt handler busy wait,
waiting for the lock?

Am I missing something here?

Rajat

> > I have written similar code in my interrupt handler (Interrupt
> > context). The driver data is not accessed from anywhere else. Is my
> > code safe from any potential concurrency issues? Is there a need to
> > use spin_lock_irqsave()? In both the places?
>
> You need to use spin_lock_irqsave() from process context.
>  From the interrupt handler itself it doesn't hurt, but it
> shouldn't matter much since interrupt handlers should not
> get preempted.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/