s390/ap: introduce mutex to lock the AP bus scan

Rework the invocations around ap_scan_bus():
- Protect ap_scan_bus() with a mutex to make sure only one
  scan at a time is running.
- The workqueue invocation which is triggered by either the
  module init or via AP bus scan timer expiration uses this
  mutex and if there is already a scan running, the work
  is simple aborted (as the job is done by another task).
- The ap_bus_force_rescan() which is invoked by higher level
  layers mostly on failures which indicate a bus scan may
  help is reworked to call ap_scan_bus() direct instead of
  enqueuing work into a system workqueue and waiting for that
  to finish. Of course the mutex is respected and in case of
  another task already running a bus scan the shortcut of
  waiting for this scan to finish and reusing the scan result
  is taken.

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Reviewed-by: Holger Dengler <dengler@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/drivers/s390/crypto/ap_bus.h b/drivers/s390/crypto/ap_bus.h
index be320bd46f65..59c7ed49aa02 100644
--- a/drivers/s390/crypto/ap_bus.h
+++ b/drivers/s390/crypto/ap_bus.h
@@ -266,7 +266,7 @@ int ap_sb_available(void);
 bool ap_is_se_guest(void);
 void ap_wait(enum ap_sm_wait wait);
 void ap_request_timeout(struct timer_list *t);
-void ap_bus_force_rescan(void);
+bool ap_bus_force_rescan(void);
 
 int ap_test_config_usage_domain(unsigned int domain);
 int ap_test_config_ctrl_domain(unsigned int domain);