ARM: Stop irqsoff trace on return to user

If the irqsoff tracer is in use, stop tracing the interrupt disable
interval when returning to userspace.  Tracing userspace execution
time as interrupts disabled time is not helpful for kernel
performance analysis purposes.  Only do so if the irqsoff tracer
is enabled, to avoid overhead purely for lockdep, which doesn't
care.

Change-Id: I74cde7dd0c4c3a783af34e76bd4efc1f85315abe
Signed-off-by: Todd Poynor <toddpoynor@google.com>
(cherry picked from commit 20713df2d48712bab9b4d690fbf838c8f3fc3927)

Signed-off-by: nobodyAtall <tsogkas@ceid.upatras.gr>
Signed-off-by: garwedgess <garethwilliams21@gmail.com>

arch/arm/kernel/entry-common.S

@@ -29,6 +29,9 @@ ret_fast_syscall:
 	ldr	r1, [tsk, #TI_FLAGS]
 	tst	r1, #_TIF_WORK_MASK
 	bne	fast_work_pending
+#if defined(CONFIG_IRQSOFF_TRACER)
+	asm_trace_hardirqs_on
+#endif
 
 	/* perform architecture specific actions before user return */
 	arch_ret_to_user r1, lr
@@ -63,6 +66,9 @@ ret_slow_syscall:
 	tst	r1, #_TIF_WORK_MASK
 	bne	work_pending
 no_work_pending:
+#if defined(CONFIG_IRQSOFF_TRACER)
+	asm_trace_hardirqs_on
+#endif
 	/* perform architecture specific actions before user return */
 	arch_ret_to_user r1, lr