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Subject[tip:sched/urgent] Revert "x86, timers: Check for pending timers after (device) interrupts"
Commit-ID:  e7ab0f7b50bc4688fb5cf65de5d42e3b882fb8d1
Gitweb: http://git.kernel.org/tip/e7ab0f7b50bc4688fb5cf65de5d42e3b882fb8d1
Author: Ingo Molnar <mingo@elte.hu>
AuthorDate: Fri, 9 Oct 2009 15:58:20 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Fri, 9 Oct 2009 15:58:20 +0200

Revert "x86, timers: Check for pending timers after (device) interrupts"

This reverts commit 9bcbdd9c58617f1301dd4f17c738bb9bc73aca70.

The real bug producing LatencyTop latencies has been fixed in:

f5dc375: sched: Update the clock of runqueue select_task_rq() selected

And the commit being reverted here triggers local timer processing
from every device IRQ. If device IRQs come in at a high frequency,
this could cause a performance regression.

The commit being reverted here purely 'fixed' the reported latency
as a side effect, because CPUs were being moved out of idle more
often.

Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Frans Pop <elendil@planet.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <20091008064041.67219b13@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
arch/x86/kernel/irq.c | 2 --
arch/x86/kernel/smp.c | 1 -
2 files changed, 0 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index 3912061..74656d1 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -244,7 +244,6 @@ unsigned int __irq_entry do_IRQ(struct pt_regs *regs)
__func__, smp_processor_id(), vector, irq);
}

- run_local_timers();
irq_exit();

set_irq_regs(old_regs);
@@ -269,7 +268,6 @@ void smp_generic_interrupt(struct pt_regs *regs)
if (generic_interrupt_extension)
generic_interrupt_extension();

- run_local_timers();
irq_exit();

set_irq_regs(old_regs);
diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
index d915d95..ec1de97 100644
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -198,7 +198,6 @@ void smp_reschedule_interrupt(struct pt_regs *regs)
{
ack_APIC_irq();
inc_irq_stat(irq_resched_count);
- run_local_timers();
/*
* KVM uses this interrupt to force a cpu out of guest mode
*/

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