[PATCH 3.12 026/212] genirq: Set the irq thread policy without checking CAP_SYS_NICE

[Greg Kroah-Hartman]

3.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Thomas Pfaff <tpf...@pcs.com>

commit bbfe65c219c638e19f1da5adab1005b2d68ca810 upstream.

In commit ee23871389 ("genirq: Set irq thread to RT priority on
creation") we moved the assigment of the thread's priority from the
thread's function into __setup_irq(). That function may run in user
context for instance if the user opens an UART node and then driver
calls requests in the ->open() callback. That user may not have
CAP_SYS_NICE and so the irq thread won't run with the SCHED_OTHER
policy.

This patch uses sched_setscheduler_nocheck() so we omit the CAP_SYS_NICE
check which is otherwise required for the SCHED_OTHER policy.

[bigeasy: Rewrite the changelog]

Signed-off-by: Thomas Pfaff <tpf...@pcs.com>
Cc: Ivo Sieben <meltedpiano...@gmail.com>
Link: 
http://lkml.kernel.org/r/1381489240-29626-1-git-send-email-bige...@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bige...@linutronix.de>
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 kernel/irq/manage.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -956,7 +956,7 @@ __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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