[3.11.y.z extended stable] Patch "genirq: Set the irq thread policy without checking CAP_SYS_NICE" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    genirq: Set the irq thread policy without checking CAP_SYS_NICE

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 76c9d3c4290534312f70ee9b3271294de5320053 Mon Sep 17 00:00:00 2001
From: Thomas Pfaff <tpfaff at pcs.com>
Date: Fri, 11 Oct 2013 13:00:40 +0200
Subject: genirq: Set the irq thread policy without checking CAP_SYS_NICE

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 <tpfaff at pcs.com>
Cc: Ivo Sieben <meltedpianoman at gmail.com>
Link: http://lkml.kernel.org/r/1381489240-29626-1-git-send-email-bigeasy@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy at linutronix.de>
Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 kernel/irq/manage.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 514bcfd..3e59f95 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -956,7 +956,7 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
 			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
--
1.8.3.2