Interrupt randomness in 3.14.10-rt

From: Ben Hutchings
Date: Thu Jul 10 2014 - 22:25:14 EST


I noticed this change between 3.14.3-rt5 and 3.14.10-rt7:

--- debian/patches/features/all/rt/random-make-it-work-on-rt.patch (revision 21522)
+++ debian/patches/features/all/rt/random-make-it-work-on-rt.patch (working copy)
[...]
---- a/kernel/irq/manage.c
-+++ b/kernel/irq/manage.c
-@@ -942,6 +942,12 @@ static int irq_thread(void *data)
- if (action_ret == IRQ_HANDLED)
- atomic_inc(&desc->threads_handled);
-
-+#ifdef CONFIG_PREEMPT_RT_FULL
-+ migrate_disable();
-+ add_interrupt_randomness(action->irq, 0,
-+ desc->random_ip ^ (unsigned long) action);
-+ migrate_enable();
-+#endif
- wake_threads_waitq(desc);
- }
-

(I.e. old patch included these additions, new patch doesn't.)

Evidently this was made in the announced 3.14.10-rt6, not -rt7. Was it
intentional? Now irq_desc::random_ip is set but never used.

Ben.

--
Ben Hutchings
To err is human; to really foul things up requires a computer.

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