On Fri 2013-07-12 10:37:33, Alan Stern wrote:
> On Fri, 12 Jul 2013, Yanmin Zhang wrote:
>
> > On Thu, 2013-07-11 at 16:03 +0800, [email protected] wrote:
> > > From: Liu ShuoX <[email protected]>
> > >
> > > In shutdown progress, system is possible to do power transition
> > > (such as suspend-to-ram) in parallel. It is unreasonable. So,
> > > fixes it by adding a system_state checking and queue try_to_suspend
> > > again when system status is not running.
> > >
> > > Signed-off-by: Liu ShuoX <[email protected]>
> > > ---
> > > kernel/power/autosleep.c | 3 ++-
> > > 1 files changed, 2 insertions(+), 1 deletions(-)
> > >
> > Without this patch, we hit an hang issue on Android.
> >
> > Scenario:
> > Kernel starts shutdown and calls all device driver's shutdown callback.
> > When a driver's shutdown is called, the last wakelock is released and
> > suspend-to-ram starts. However, as some driver's shut down callbacks
> > already shut down devices and disable runtime pm, the suspend-to-ram
> > calls driver's suspend callback without noticing that device is already
> > off and causes crash.
> > We know the drivers should be fixed, but can we also change generic
> > codes a little to make it stronger?
>
> Indeed, this does seem like the sort of thing we want to have.
> Allowing an "automatic" or "opportunistic" sleep in the middle of a
> shutdown makes no sense at all. In fact, it might be a good idea to
> disable system sleep completely at this time -- not even a write to
> /sys/power/state should be allowed to interrupt a shutdown.
I'm not completely sure, but as long as userland is running, we should
have system_state == RUNNING, no?
Pavel
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