Messages in this thread | | | Date | Tue, 30 Jan 2001 09:44:21 -0600 | From | Joe deBlaquiere <> | Subject | Re: [linux-audio-dev] low-latency scheduling patch for 2.4.0 |
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David Woodhouse wrote:
> jadb@redhat.com said: > >> (If you're running a program XIP from flash and a RT interrupt leaves >> the flash in a unreadable state, boom!). > > > Bad example. I don't expect Linux to support writable XIP any time in the > near future. The only thing I envisage myself doing to help people who want > writable XIP is to take away their crackpipe. >
I wasn't thinking of running the kernel XIP from writable, but even trying to do that from the filesystem is a mess. If you're going to be that way about it...
/me hands over the crackpipe
> Until we get dual-port flash, of course. > > The thing that really does concern me about the flash driver code is the > fact that it often wants to wait for about 100µs. On machines with > HZ==100, that sucks if you use udelay() and it sucks if you schedule(). So > we end up dropping the spinlock (so at least bottom halves can run again) > and calling: > > static inline void cfi_udelay(int us) > { > if (current->need_resched) > schedule(); > else > udelay(us); > } >
The locical answer is run with HZ=10000 so you get 100us intervals, right ;o). On systems with multiple hardware timers you could kick off a single event at 200us, couldn't you? I've done that before with the extra timer assigned exclusively to a resource. It's not a giant time slice, but at least you feel like you're allowing something to happen, right?
> > -- > dwmw2
-- Joe
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