[S390] lockdep: trace hardirq off in smp_send_stop

With lockdep we got the following trace after a panic:

Badness at /home/autobuild/BUILD/linux-2.6.28-20090204/kernel/lockdep.c:2878
[...]
Call Trace:
 [<0000000000176334>] lock_acquire+0x54/0xbc
 [<000000000050b4fe>] __atomic_notifier_call_chain+0x6e/0xdc
 [<000000000050b59c>] atomic_notifier_call_chain+0x30/0x44
 [<0000000000504274>] panic+0xd0/0x1e8
[...]
INFO: lockdep is turned off.
Last Breaking-Event-Address:
 [<0000000000170e62>] check_flags+0xae/0x15c
possible reason: unannotated irqs-off.

lockdep is right. We missed a trace_hardirq_off in our smp_send_stop
function and smp_send_stop is called before the panic call chain.

Reported-by: Mijo <Safradin mijo@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/smp.c

@@ -32,6 +32,7 @@
 #include <linux/delay.h>
 #include <linux/cache.h>
 #include <linux/interrupt.h>
+#include <linux/irqflags.h>
 #include <linux/cpu.h>
 #include <linux/timex.h>
 #include <linux/bootmem.h>
@@ -75,6 +76,7 @@ void smp_send_stop(void)
 
 	/* Disable all interrupts/machine checks */
 	__load_psw_mask(psw_kernel_bits & ~PSW_MASK_MCHECK);
+	trace_hardirqs_off();
 
 	/* stop all processors */
 	for_each_online_cpu(cpu) {