sched/fair: Fix new task's load avg removed from source CPU in wake_up_new_task()
authorYuyang Du <yuyang.du@intel.com>
Wed, 16 Dec 2015 23:34:27 +0000 (07:34 +0800)
committerIngo Molnar <mingo@kernel.org>
Wed, 6 Jan 2016 10:06:29 +0000 (11:06 +0100)
commit0905f04eb21fc1c2e690bed5d0418a061d56c225
tree453158d4e26692cbd1244bf14fdc7dd2ffd9ac96
parent5a1078043f844074cbd53981432778a8d5dd56e9
sched/fair: Fix new task's load avg removed from source CPU in wake_up_new_task()

If a newly created task is selected to go to a different CPU in fork
balance when it wakes up the first time, its load averages should
not be removed from the source CPU since they are never added to
it before. The same is also applicable to a never used group entity.

Fix it in remove_entity_load_avg(): when entity's last_update_time
is 0, simply return. This should precisely identify the case in
question, because in other migrations, the last_update_time is set
to 0 after remove_entity_load_avg().

Reported-by: Steve Muckle <steve.muckle@linaro.org>
Signed-off-by: Yuyang Du <yuyang.du@intel.com>
[peterz: cfs_rq_last_update_time]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Juri Lelli <Juri.Lelli@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Morten Rasmussen <morten.rasmussen@arm.com>
Cc: Patrick Bellasi <patrick.bellasi@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Link: http://lkml.kernel.org/r/20151216233427.GJ28098@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
kernel/sched/fair.c