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Subject[PATCH] 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>
---
Compile tested only. It would be great if someone w/ affected
configuraiton can test this.

Thank you.

drivers/char/apm-emulation.c | 16 ++++++----------
1 file changed, 6 insertions(+), 10 deletions(-)

Index: work/drivers/char/apm-emulation.c
===================================================================
--- work.orig/drivers/char/apm-emulation.c
+++ work/drivers/char/apm-emulation.c
@@ -300,17 +300,13 @@ apm_ioctl(struct file *filp, u_int cmd,
/*
* 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;

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