Commit 9a1c4fb5 authored by Zhang Qiao's avatar Zhang Qiao Committed by sanglipeng
Browse files

sched/fair: sanitize vruntime of entity being placed

stable inclusion
from stable-v5.10.177
commit dfdcda25fb5e3c09394a28173f24b22e7c7e4731
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I88YNP

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=dfdcda25fb5e3c09394a28173f24b22e7c7e4731



--------------------------------

commit 829c1651 upstream.

When a scheduling entity is placed onto cfs_rq, its vruntime is pulled
to the base level (around cfs_rq->min_vruntime), so that the entity
doesn't gain extra boost when placed backwards.

However, if the entity being placed wasn't executed for a long time, its
vruntime may get too far behind (e.g. while cfs_rq was executing a
low-weight hog), which can inverse the vruntime comparison due to s64
overflow.  This results in the entity being placed with its original
vruntime way forwards, so that it will effectively never get to the cpu.

To prevent that, ignore the vruntime of the entity being placed if it
didn't execute for much longer than the characteristic sheduler time
scale.

[rkagan: formatted, adjusted commit log, comments, cutoff value]
Signed-off-by: default avatarZhang Qiao <zhangqiao22@huawei.com>
Co-developed-by: default avatarRoman Kagan <rkagan@amazon.de>
Signed-off-by: default avatarRoman Kagan <rkagan@amazon.de>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20230130122216.3555094-1-rkagan@amazon.de


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarsanglipeng <sanglipeng1@jd.com>
parent afe4bac1
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