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>

2 files changed, 1 insertions, 4 deletions

diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index 29eb805ea4a6..c1d6555d2567 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 24a921bcf04f..f42ff97e1f8f 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