[PATCH 1/2] irq: Remove IRQ_EXIT_OFFSET workaround

From: Frederic Weisbecker
Date: Thu Feb 28 2013 - 15:03:27 EST


The IRQ_EXIT_OFFSET trick was used to make sure the irq
doesn't get preempted after we substract the HARDIRQ_OFFSET
until we are entirely done with any code in irq_exit().

This workaround was necessary because some archs may call
irq_exit() with irqs enabled and there is still some code
in the end of this function that is not covered by the
HARDIRQ_OFFSET but want to stay non-preemptible.

Now that irq are always disabled in irq_exit(), the whole code
is guaranteed not to be preempted. We can thus remove this hack.

Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
include/linux/hardirq.h | 2 --
kernel/softirq.c | 3 +--
2 files changed, 1 insertions(+), 4 deletions(-)

diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index 29eb805..c1d6555 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -118,10 +118,8 @@

#ifdef CONFIG_PREEMPT_COUNT
# define preemptible() (preempt_count() == 0 && !irqs_disabled())
-# define IRQ_EXIT_OFFSET (HARDIRQ_OFFSET-1)
#else
# define preemptible() 0
-# define IRQ_EXIT_OFFSET HARDIRQ_OFFSET
#endif

#if defined(CONFIG_SMP) || defined(CONFIG_GENERIC_HARDIRQS)
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 24a921b..f42ff97 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -343,7 +343,7 @@ void irq_exit(void)

account_irq_exit_time(current);
trace_hardirq_exit();
- sub_preempt_count(IRQ_EXIT_OFFSET);
+ sub_preempt_count(HARDIRQ_OFFSET);
if (!in_interrupt() && local_softirq_pending())
invoke_softirq();

@@ -353,7 +353,6 @@ void irq_exit(void)
tick_nohz_irq_exit();
#endif
rcu_irq_exit();
- sched_preempt_enable_no_resched();
#ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED
local_irq_restore(flags);
#endif
--
1.7.5.4

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