Commit 613f5d13 authored by Colin Cross's avatar Colin Cross Committed by Rafael J. Wysocki
Browse files

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: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarPavel Machek <pavel@ucw.cz>
Signed-off-by: default avatarColin Cross <ccross@android.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 18ad0c62
......@@ -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);
......
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