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irq: Remove IRQ_EXIT_OFFSET workaround 

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@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Frederic Weisbecker 2013-02-22 00:05:07 +01:00
parent af7bdbafe3
commit 4d4c4e24cf
2 changed files with 1 additions and 4 deletions
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2
include/linux/hardirq.h
View File

@ -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)

3
kernel/softirq.c
View File

@ -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