apm-emulation: use wait_event_freezable() instead of freezer_[do_not_]count()

vfork is moving away from freezer_[do_not_]count() one way or the
other leaving apm_ioctl() as the only user.  apm_ioctl() just wants to
wait for suspend/resume cycle to complete without hindering the
freezer.  Use wait_event_freezable() instead.

The only annoyance is that wait_event_freezable() wakes up with
-ERESTART if there are pending signals while apm_ioctl() wants to
ignore all signals until suspend is complete.  We can play with
@current->[real_]blocked but this is hardly a performance or latency
critical path - simply chill a bit on each iteration until
SUSPEND_DONE for unlikely cases where there are pending signals.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

diff --git a/drivers/char/apm-emulation.c b/drivers/char/apm-emulation.c
index 548708c..7e2709c 100644 (file)
--- a/drivers/char/apm-emulation.c
+++ b/drivers/char/apm-emulation.c
@@ -300,17 +300,13 @@ apm_ioctl(struct file *filp, u_int cmd, u_long arg)
                        /*
                         * Wait for the suspend/resume to complete.  If there
                         * are pending acknowledges, we wait here for them.
                        /*
                         * Wait for the suspend/resume to complete.  If there
                         * are pending acknowledges, we wait here for them.

+                        * wait_event_freezable() is interruptible and pending
+                        * signal can cause busy looping.  We aren't doing
+                        * anything critical, chill a bit on each iteration.

                         */
                         */

-                       freezer_do_not_count();
-
-                       wait_event(apm_suspend_waitqueue,
-                                  as->suspend_state == SUSPEND_DONE);
-
-                       /*
-                        * Since we are waiting until the suspend is done, the
-                        * try_to_freeze() in freezer_count() will not trigger
-                        */
-                       freezer_count();
+                       while (wait_event_freezable(apm_suspend_waitqueue,
+                                       as->suspend_state == SUSPEND_DONE))
+                               msleep(10);

                        break;
                case SUSPEND_ACKTO:
                        as->suspend_result = -ETIMEDOUT;
                        break;
                case SUSPEND_ACKTO:
                        as->suspend_result = -ETIMEDOUT;