linux-kernel - Interrupt randomness in 3.14.10-rt

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Date:	Fri, 11 Jul 2014 03:24:52 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>, stable-rt@...r.kernel.org
Subject: Interrupt randomness in 3.14.10-rt

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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