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author | Colin Cross <ccross@android.com> | 2013-05-06 23:50:11 +0000 |
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committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2013-05-12 14:16:22 +0200 |
commit | 613f5d13b569859171f0896fbc73ee0bfa811fda (patch) | |
tree | 92f3f25db1fe1063624cc0ef69506d2f38a1988a /kernel/freezer.c | |
parent | 18ad0c6297df1d671ecea83b608cd9e432642a05 (diff) | |
download | kernel_goldelico_gta04-613f5d13b569859171f0896fbc73ee0bfa811fda.zip kernel_goldelico_gta04-613f5d13b569859171f0896fbc73ee0bfa811fda.tar.gz kernel_goldelico_gta04-613f5d13b569859171f0896fbc73ee0bfa811fda.tar.bz2 |
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>
Diffstat (limited to 'kernel/freezer.c')
-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 c38893b..8b2afc1 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); |