Scott Wood wrote:

Anton Vorontsov wrote:

quoted

As the compromise I might suggest this: forbid pattern_start/pattern_end
from the ISRs (by marking them as might_sleep()), and replace _irqsave
spinlock with simple spinlock.

No, you cannot use a bare spinlock with IRQs enabled.  You'll deadlock 
on SMP, and you'll have races with preemption enabled.

Sorry, brain fart...  obviously, with preemption on it'd disable 
preemption even with a plain spinlock, and on SMP without preemption 
it's not an issue.

Still, all you're getting rid of is the MSR twiddling, which should be 
pretty minor.

-Scott