On Thu, 2007-03-22 at 00:29 +0530, anubhav rakshit wrote: > On 3/21/07, Arjan van de Ven <[EMAIL PROTECTED]> wrote: > > On Wed, 2007-03-21 at 09:23 +0530, Rajat Jain wrote: > > > Hi, > > > > > > 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. > how is it optimal,when all you require is to disable just one particular IRQ?
because if you don't disable all you increase hold times, which increases contention. Contention is BAD. > > > 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... > Aren't we increasing the latency because of this scheme? very very tiny amounts; since typically lock hold times are really short -- if you want to mail me at work (you don't), use arjan (at) linux.intel.com Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org - To unsubscribe from this list: send the line "unsubscribe linux-newbie" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.linux-learn.org/faqs
