On 4/4/07, Rajat Jain <[EMAIL PROTECTED]> wrote:
> > We often have a case where a driver wants to access its data structure
> > in process context as well as in interrupt context (in its ISR). In
> > such scenarios, we generally use spin_lock_irqsave() to grab the lock
> > as well as disable all the local interrupts. AFAIK, disabling of local
> > interrupts is required so as to avoid running your ISR (which needs
> > the lock) while process context is holding the lock. However, this
> > also disables any other ISRs (which DO NOT need the lock) on the local
> > processor.
> >
> > Isn't this sub-optimal? Shouldn't there be a finer grained locking?
>
> actually it's optimal.
> It's fastest to delay the interrupts a little and be done with what you
> want to do under the lock quickly, and THEN take the interrupt. This
> means the lock hold time is short, which significantly reduces
> contention on this lock...
So on the same lines, if a data structure is accessed in both process
context and in a (single) driver ISR, should a driver use
spin_lock_irqsave() to get the lock in ISR? Or will a simple
spin_lock() suffice?
a simple spin_lock() should do,as in Linux the ISR's are not
recursive,and you just need protection in a single ISR.
Anubhav Rakshit
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