Messages in this thread | | | Subject | Re: Using random in interrupts for RT | From | Steven Rostedt <> | Date | Tue, 21 Aug 2012 14:12:13 -0400 |
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On Tue, 2012-08-14 at 10:30 -0400, Steven Rostedt wrote: > Thomas, > > Ben Hutchings asked me if we still need "genirq: Disable random call on > preempt-rt" for -rt? With commit 902c098a366 "random: use lockless > techniques in the interrupt path" there is no more locks used. But does > it still produce high latencies?
Ben,
Looks that the #ifndef can't be removed just yet. The code is not totally lockless...
add_interrupt_randomness -> credit_entropy_bits -> kill_fasync -> kill_fasync_rcu -> spin_lock_irqsave(&fa->fa_lock, flags)
to make things worse, that spinlock turns into a mutex on -rt, so it may crash the box if triggered.
-- Steve
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