Messages in this thread | | | Date | Sun, 27 Dec 2009 13:28:37 +0100 | From | Alain Knaff <> | Subject | Re: [Fdutils] DMA cache consistency bug introduced in 2.6.28 |
| |
Andi Kleen wrote: >>> Does pmqos work with apci=off etc.? >> yes >> >>> I didn't think it shut down >>> the classic "HLT" idle, does it? >> it does if you specify a latency of 0; it will then go into the >> spin-only state until you give up your latency requirement > > I looked at it this evening, but it seems like pm_qos is not > interrupt safe (e.g. calls blocking notifiers) and floppy currently does > enable/disable_hlt from interrupts and bottom halves. > > Would need some more infrastructure work or restructuring > of the floppy driver. > > -Andi
disable_hlt/enable_hlt was only needed to work around a bug on TM4000 (Texas Instrument) Laptops which were popular around 1994 / 1995. Basically, as soon as the CPU went into hlt() state, so did the DMA controller, either causing a really slow transfer, or (worse) a buffer over/underrun which failed the operation.
On hardware unaffected by this particular bug (which would be most hardware around now, 14 years after the fact...), these calls can safely be removed.
Regards,
Alain
| |