softirq/preempt: Add missing current->preempt_disable_ip update

While debugging some "sleeping function called from invalid context" bug I
realized that the debugging message "Preemption disabled at:" pointed to
an incorrect function.

In particular if the last function/action that disabled preemption was
spin_lock_bh() then current->preempt_disable_ip won't be updated.

The reason for this is that __local_bh_disable_ip() will increase
preempt_count manually instead of calling preempt_count_add(), which
would handle the update correctly.

It look like the manual handling was done to work around some lockdep issue.

So add the missing update of current->preempt_disable_ip to
__local_bh_disable_ip() as well.

Signed-off-by: Heiko Carstens <[e-mail]>
Signed-off-by: Peter Zijlstra (Intel) <[e-mail]>
Cc: Paul E. McKenney <[e-mail]>
Cc: Andrew Morton <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Link: http://lkml.kernel.org/r/20150107090441.GC4365@osiris
Signed-off-by: Ingo Molnar <[e-mail]>

kernel/softirq.c

···
 		trace_softirqs_off(ip);
 	raw_local_irq_restore(flags);
 
-	if (preempt_count() == cnt)
+	if (preempt_count() == cnt) {
+#ifdef CONFIG_DEBUG_PREEMPT
+		current->preempt_disable_ip = get_parent_ip(CALLER_ADDR1);
+#endif
 		trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1));
+	}
 }
 EXPORT_SYMBOL(__local_bh_disable_ip);
 #endif /* CONFIG_TRACE_IRQFLAGS */