Hello Matthew,
On Wed, 19 May 2010, Matthew Garrett wrote:
> On Wed, May 19, 2010 at 10:17:01AM -0600, Paul Walmsley wrote:
>
> > Could you please elaborate, or provide a link to an E-mail in the archives
> > that would explain why?
>
> What would otherwise be a wakeup event may be delivered between you
> deciding to stop tasks and you actually stopping tasks. How do you know
> to restart tasks at that point?
The original message you sent[1] quoted this part[2] of the proposal:
----
A. To prevent untrusted process timers from waking the system,
the processes can be run in a cgroup that calls
del_timer_sync() on all process timers upon receipt of some
trigger. When the system returns from the system low-power
state and some trigger event happens, add_timer() can be
called to add all the cgroup's timers back.
----
That isn't intended to address the task restarting problem. The task
restarting problem is intended to be addressed by this part[3]:
----
B. To prevent untrusted processes from hogging CPUs, the
processes can be run in a cgroup that puts all threads in
TASK_RUNNING processes into TASK_INTERRUPTIBLE state and
calls schedule() [6], upon receipt of some trigger. This
should allow processes to be awakened by an external system
event, e.g., network packet received. When the system
returns from the system low-power state and some trigger
event happens, those process threads can be placed back into
TASK_RUNNING state and rescheduled.
----
It sounds like Android doesn't even need to use full system suspend if
some proposal like (A) and (B) are implemented[4]. In that case, all the
code that deals with races in full system suspend (like suspend blockers)
can be dropped.
- Paul
1. Matthew Garrett E-mail to the linux-pm mailing list, dated Tue May 18
02:55:19 +0100
https://lists.linux-foundation.org/pipermail/linux-pm/2010-May/025664.html
2. Paragraph B4A of Paul Walmsley E-mail to the linux-pm mailing list,
dated Mon May 17 19:39:44 CDT 2010:
https://lists.linux-foundation.org/pipermail/linux-pm/2010-May/025663.html
3. Paragraph B4B of Paul Walmsley E-mail to the linux-pm mailing list,
dated Mon May 17 19:39:44 CDT 2010:
https://lists.linux-foundation.org/pipermail/linux-pm/2010-May/025663.html
4. Arve Hjønnevåg E-mail to the linux-pm mailing list, dated Mon, May 17
20:06:33 PDT 2010:
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