On Tue, 2014-01-07 at 10:18 +0000, dongsheng.w...@freescale.com wrote: > > > -----Original Message----- > > From: Benjamin Herrenschmidt [mailto:b...@kernel.crashing.org] > > Sent: Tuesday, January 07, 2014 1:50 PM > > To: Wang Dongsheng-B40534 > > Cc: Wood Scott-B07421; linuxppc-dev@lists.ozlabs.org > > Subject: Re: [PATCH] powerpc/mpic: supply a .disable callback > > > > On Tue, 2014-01-07 at 13:38 +0800, Dongsheng Wang wrote: > > > From: Wang Dongsheng <dongsheng.w...@freescale.com> > > > > > > Currently MPIC provides .mask, but not .disable. This means that > > > effectively disable_irq() soft-disables the interrupt, and you get > > > a .mask call if an interrupt actually occurs. > > > > > > I'm not sure if this was intended as a performance benefit (it seems > > > common > > > to omit .disable on powerpc interrupt controllers, but nowhere else), but > > > it > > > interacts badly with threaded/workqueue interrupts (including KVM > > > reflection). In such cases, where the real interrupt handler does a > > > disable_irq_nosync(), schedules defered handling, and returns, we get two > > > interrupts for every real interrupt. The second interrupt does nothing > > > but see that IRQ_DISABLED is set, and decide that it would be a good > > > idea to actually call .mask. > > > > We probably don't want to do that for edge, only level interrupts. > > > Sorry Ben, I am not understand your comments. > > This issue is the kernel api irq_disable() only use chip->irq_disable(), but > mpic > not have this interface so we don't real disable the interrupt.
Yes, because we want to keep the existing behaviour of "lazy disable" for edge interrupts. It's faster. Cheers, Ben. > -Dongsheng > > > Cheers, > > Ben. > > > _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
