PM: Prevent waiting forever on asynchronous resume after abort
authorColin Cross <ccross@android.com>
Thu, 2 Sep 2010 01:35:55 +0000 (18:35 -0700)
committerDan Willemsen <dwillemsen@nvidia.com>
Thu, 1 Dec 2011 05:38:20 +0000 (21:38 -0800)
commitd0add622e869a057c793165bddfb4b8c5d7ced36
treec7e078800b572567672a76d07a995de941000870
parent4821b01af559f225600d4c3b303d89f9ca4f765b
PM: Prevent waiting forever on asynchronous resume after abort

Only wait on a parent device during resume if the parent device is
suspended.

Consider three drivers, A, B, and C.  The parent of A is C, and C
has async_suspend set.  On boot, C->power.completion is initialized
to 0.

During the first suspend:
suspend_devices_and_enter(...)
 dpm_resume(...)
  device_suspend(A)
  device_suspend(B) returns error, aborts suspend
 dpm_resume_end(...)
   dpm_resume(...)
    device_resume(A)
     dpm_wait(A->parent == C)
      wait_for_completion(C->power.completion)

The wait_for_completion will never complete, because
complete_all(C->power.completion) will only be called from
device_suspend(C) or device_resume(C), neither of which is called
if suspend is aborted before C.

After a successful suspend->resume cycle, where B doesn't abort
suspend, C->power.completion is left in the completed state by the
call to device_resume(C), and the same call path will work if B
aborts suspend.

Signed-off-by: Colin Cross <ccross@android.com>
drivers/base/power/main.c