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Subject[PATCH RT 19/25][RFC 3.0.23-rt39-rc1] timer: Fix hotplug for -rt
From: Steven Rostedt <rostedt@goodmis.org>

Revert the RT patch:
Author: Ingo Molnar <mingo@elte.hu>
Date: Fri Jul 3 08:30:32 2009 -0500
timers: fix timer hotplug on -rt

Here we are in the CPU_DEAD notifier, and we must not sleep nor
enable interrupts.

There's no problem with sleeping in this notifier.

But the get_cpu_var() had to be converted to a get_local_var().

Replace the previous fix with the get_local_var() convert.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Carsten Emde <C.Emde@osadl.org>
Cc: John Kacur <jkacur@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Clark Williams <clark.williams@gmail.com>
Cc: stable-rt@vger.kernel.org
Link: http://lkml.kernel.org/r/20120301190344.948157137@goodmis.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/timer.c | 16 +++++-----------
1 files changed, 5 insertions(+), 11 deletions(-)
diff --git a/kernel/timer.c b/kernel/timer.c
index 937799f..a319c6a 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -1743,21 +1743,17 @@ static void __cpuinit migrate_timers(int cpu)
{
struct tvec_base *old_base;
struct tvec_base *new_base;
- unsigned long flags;
int i;

BUG_ON(cpu_online(cpu));
old_base = per_cpu(tvec_bases, cpu);
- new_base = get_cpu_var(tvec_bases);
+ new_base = get_local_var(tvec_bases);
/*
* The caller is globally serialized and nobody else
* takes two locks at once, deadlock is not possible.
*/
- local_irq_save(flags);
- while (!spin_trylock(&new_base->lock))
- cpu_relax();
- while (!spin_trylock(&old_base->lock))
- cpu_relax();
+ spin_lock_irq(&new_base->lock);
+ spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);

BUG_ON(old_base->running_timer);

@@ -1771,10 +1767,8 @@ static void __cpuinit migrate_timers(int cpu)
}

spin_unlock(&old_base->lock);
- spin_unlock(&new_base->lock);
- local_irq_restore(flags);
-
- put_cpu_var(tvec_bases);
+ spin_unlock_irq(&new_base->lock);
+ put_local_var(tvec_bases);
}
#endif /* CONFIG_HOTPLUG_CPU */

--
1.7.8.3



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