On 4/4/07, Rajat Jain <rajat.noida.india@xxxxxxxxx> 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 - To unsubscribe from this list: send the line "unsubscribe linux-newbie" 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.linux-learn.org/faqs
