diff options
| author | Colin Cross <ccross@android.com> | 2013-05-06 23:50:11 +0000 |
|---|---|---|
| committer | Dan Willemsen <dwillemsen@nvidia.com> | 2013-08-30 19:10:55 -0700 |
| commit | 872e91dfc6e4903a9934a61a6f271d1020cf65b7 (patch) | |
| tree | 2ba18193ad89f071d15ef35c68f01669e6dd9aa2 /kernel | |
| parent | 58ca5cf8456cc2f5a7915495fd057f81bfab99b6 (diff) | |
UPSTREAM next (v3.11): freezer: skip waking up tasks with PF_FREEZER_SKIP set
Android goes through suspend/resume very often (every few seconds when
on a busy wifi network with the screen off), and a significant portion
of the energy used to go in and out of suspend is spent in the
freezer. If a task has called freezer_do_not_count(), don't bother
waking it up. If it happens to wake up later it will call
freezer_count() and immediately enter the refrigerator.
Combined with patches to convert freezable helpers to use
freezer_do_not_count() and convert common sites where idle userspace
tasks are blocked to use the freezable helpers, this reduces the
time and energy required to suspend and resume.
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Colin Cross <ccross@android.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
(cherry picked from commit 613f5d13b569859171f0896fbc73ee0bfa811fda)
Change-Id: I184a3a065f0c6b951dc129c722f6e42268da81f7
Reviewed-on: http://git-master/r/228691
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Prashant Gaikwad <pgaikwad@nvidia.com>
Tested-by: Prashant Gaikwad <pgaikwad@nvidia.com>
Reviewed-by: Bharat Nihalani <bnihalani@nvidia.com>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/freezer.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/kernel/freezer.c b/kernel/freezer.c index c38893b0efba..8b2afc1c9df0 100644 --- a/kernel/freezer.c +++ b/kernel/freezer.c @@ -110,6 +110,18 @@ bool freeze_task(struct task_struct *p) { unsigned long flags; + /* + * This check can race with freezer_do_not_count, but worst case that + * will result in an extra wakeup being sent to the task. It does not + * race with freezer_count(), the barriers in freezer_count() and + * freezer_should_skip() ensure that either freezer_count() sees + * freezing == true in try_to_freeze() and freezes, or + * freezer_should_skip() sees !PF_FREEZE_SKIP and freezes the task + * normally. + */ + if (freezer_should_skip(p)) + return false; + spin_lock_irqsave(&freezer_lock, flags); if (!freezing(p) || frozen(p)) { spin_unlock_irqrestore(&freezer_lock, flags); |