core: Do not disable interrupts on RT in res_counter.c

Frederic Weisbecker reported this warning:

[   45.228562] BUG: sleeping function called from invalid context at kernel/rtmutex.c:683
[   45.228571] in_atomic(): 0, irqs_disabled(): 1, pid: 4290, name: ntpdate
[   45.228576] INFO: lockdep is turned off.
[   45.228580] irq event stamp: 0
[   45.228583] hardirqs last  enabled at (0): [<(null)>] (null)
[   45.228589] hardirqs last disabled at (0): [<ffffffff8025449d>] copy_process+0x68d/0x1500
[   45.228602] softirqs last  enabled at (0): [<ffffffff8025449d>] copy_process+0x68d/0x1500
[   45.228609] softirqs last disabled at (0): [<(null)>] (null)
[   45.228617] Pid: 4290, comm: ntpdate Tainted: G        W  2.6.29-rc4-rt1-tip #1
[   45.228622] Call Trace:
[   45.228632]  [<ffffffff8027dfb0>] ? print_irqtrace_events+0xd0/0xe0
[   45.228639]  [<ffffffff8024cd73>] __might_sleep+0x113/0x130
[   45.228646]  [<ffffffff8077c811>] rt_spin_lock+0xa1/0xb0
[   45.228653]  [<ffffffff80296a3d>] res_counter_charge+0x5d/0x130
[   45.228660]  [<ffffffff802fb67f>] __mem_cgroup_try_charge+0x7f/0x180
[   45.228667]  [<ffffffff802fc407>] mem_cgroup_charge_common+0x57/0x90
[   45.228674]  [<ffffffff80212096>] ? ftrace_call+0x5/0x2b
[   45.228680]  [<ffffffff802fc49d>] mem_cgroup_newpage_charge+0x5d/0x60
[   45.228688]  [<ffffffff802d94ce>] __do_fault+0x29e/0x4c0
[   45.228694]  [<ffffffff8077c843>] ? rt_spin_unlock+0x23/0x80
[   45.228700]  [<ffffffff802db8b5>] handle_mm_fault+0x205/0x890
[   45.228707]  [<ffffffff80212096>] ? ftrace_call+0x5/0x2b
[   45.228714]  [<ffffffff8023495e>] do_page_fault+0x11e/0x2a0
[   45.228720]  [<ffffffff8077e5a5>] page_fault+0x25/0x30
[   45.228727]  [<ffffffff8043e1ed>] ? __clear_user+0x3d/0x70
[   45.228733]  [<ffffffff8043e1d1>] ? __clear_user+0x21/0x70

The reason is the raw IRQ flag use of kernel/res_counter.c.

The irq flags tricks there seem a bit pointless: it cannot protect the
c->parent linkage because local_irq_save() is only per CPU.

So replace it with _nort(). This code needs a second look.
Reported-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

kernel/res_counter.c

@@ -14,6 +14,7 @@
 #include <linux/res_counter.h>
 #include <linux/uaccess.h>
 #include <linux/mm.h>
+#include <linux/interrupt.h>
 
 void res_counter_init(struct res_counter *counter, struct res_counter *parent)
 {
@@ -43,7 +44,7 @@ int res_counter_charge(struct res_counter *counter, unsigned long val,
 	struct res_counter *c, *u;
 
 	*limit_fail_at = NULL;
-	local_irq_save(flags);
+	local_irq_save_nort(flags);
 	for (c = counter; c != NULL; c = c->parent) {
 		spin_lock(&c->lock);
 		ret = res_counter_charge_locked(c, val);
@@ -62,7 +63,7 @@ undo:
 		spin_unlock(&u->lock);
 	}
 done:
-	local_irq_restore(flags);
+	local_irq_restore_nort(flags);
 	return ret;
 }
 
@@ -79,13 +80,13 @@ void res_counter_uncharge(struct res_counter *counter, unsigned long val)
 	unsigned long flags;
 	struct res_counter *c;
 
-	local_irq_save(flags);
+	local_irq_save_nort(flags);
 	for (c = counter; c != NULL; c = c->parent) {
 		spin_lock(&c->lock);
 		res_counter_uncharge_locked(c, val);
 		spin_unlock(&c->lock);
 	}
-	local_irq_restore(flags);
+	local_irq_restore_nort(flags);
 }