linux-kernel - [PATCH] genirq: Set the irq thread policy without checking CAP_SYS

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Message-Id: <1381489240-29626-1-git-send-email-bigeasy@linutronix.de>
Date:	Fri, 11 Oct 2013 13:00:40 +0200
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Ivo Sieben <meltedpianoman@...il.com>,
	Thomas Pfaff <tpfaff@....com>, linux-kernel@...r.kernel.org,
	linux-rt-users@...r.kernel.org,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: [PATCH] genirq: Set the irq thread policy without checking CAP_SYS_NICE

From: Thomas Pfaff <tpfaff@....com>

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.

Cc: Ivo Sieben <meltedpianoman@...il.com>
Cc: stable@...r.kernel.org
Signed-off-by: Thomas Pfaff <tpfaff@....com>
[bigeasy: rewrite the changelog]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 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
-- 
1.8.4.rc3

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