On Tue, Apr 02, 2019 at 08:43:51AM +0000, Rasmus Villemoes wrote: > Thanks! There's one other option I can think of: don't do the interrupts > at all, but just busy-wait for the completion of each word transfer (in > a cpu_relax() loop). That could be guarded by something like > 1000000*bits_per_word < hz (roughly, the word transfer takes less than 1 > us). At least on -rt, having the interrupt thread scheduled in and out > again easily takes more than 1us of cpu time, and AFAIU we'd still be > preemptible throughout - and/or one can throw in a cond_resched() every > nnn words. But this might be a bit -rt specific, and the 1us threshold > is rather arbitrary. Yeah, that's definitely worth exploring as a mitigation but obviously with things like flash I/O that gets a bit rude. Hopefully what's there at the minute turns out to be robust enough.
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