Messages in this thread Patch in this message | | | Date | Thu, 18 Aug 2011 10:06:53 +0200 | From | Tejun Heo <> | Subject | [PATCH] apm-emulation: use wait_event_freezable() instead of freezer_[do_not_]count() |
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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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