[PATCH 3.4.62-rt77] fix irq thread scheduling

[Thomas Pfaff <tpfaff@xxxxxxx>]

If an irq is requested during device open, for example by opening a serial 
device, then request_irq is called in the context of the opening process.
If the process lacks off CAP_SYS_NICE the irq thread is running with SCHED_OTHER 
priority.

The problem exists in other real time patches as well, 3.10 seems to be ok.

Signed-off-by: Thomas Pfaff <tpfaff@xxxxxxx>
---
diff -urp linux-3.4.62-rt.old/kernel/irq/manage.c linux-3.4.62-rt/kernel/irq/manage.c
--- linux-3.4.62-rt.old/kernel/irq/manage.c	2013-09-16 10:13:15.365559288 +0200
+++ linux-3.4.62-rt/kernel/irq/manage.c	2013-09-19 10:22:40.092831656 +0200
@@ -1024,7 +1024,7 @@ __setup_irq(unsigned int irq, struct irq
 			goto out_mput;
 		}
 
-		sched_setscheduler(t, SCHED_FIFO, &param);
+		sched_setscheduler_nocheck(t, SCHED_FIFO, &param);
 
 		/*
 		 * We keep the reference to the task struct even if
--
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