Interrupt randomness in 3.14.10-rt

Interrupt randomness in 3.14.10-rt

[Ben Hutchings]

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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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Re: Interrupt randomness in 3.14.10-rt

[Thomas Gleixner]

On Fri, 11 Jul 2014, Ben Hutchings wrote:

> 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.

Hmm, how did I lose that one? Thanks for spotting it! I'll pick it up for rt8

     tglx