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sched/uclamp: Fix fits_capacity() check in feec()

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commit 244226035a1f9b2b6c326e55ae5188fab4f428cb upstream.

As reported by Yun Hsiang [1], if a task has its uclamp_min >= 0.8 * 1024,
it'll always pick the previous CPU because fits_capacity() will always
return false in this case.

The new util_fits_cpu() logic should handle this correctly for us beside
more corner cases where similar failures could occur, like when using
UCLAMP_MAX.

We open code uclamp_rq_util_with() except for the clamp() part,
util_fits_cpu() needs the 'raw' values to be passed to it.

Also introduce uclamp_rq_{set, get}() shorthand accessors to get uclamp
value for the rq. Makes the code more readable and ensures the right
rules (use READ_ONCE/WRITE_ONCE) are respected transparently.

[1] https://lists.linaro.org/pipermail/eas-dev/2020-July/001488.html

Fixes: 1d42509e47 ("sched/fair: Make EAS wakeup placement consider uclamp restrictions")
Reported-by: Yun Hsiang <hsiang023167@gmail.com>
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220804143609.515789-4-qais.yousef@arm.com
(cherry picked from commit 244226035a1f9b2b6c326e55ae5188fab4f428cb)
[Fix trivial conflict in kernel/sched/fair.c due to new automatic
variables in master vs 5.10]
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Qais Yousef
2023-04-18 15:09:35 +01:00
committed by Greg Kroah-Hartman
parent 5cb1a56ced
commit 8ca2bf63d9
3 changed files with 68 additions and 10 deletions
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10
kernel/sched/core.c
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@@ -980,7 +980,7 @@ static inline void uclamp_idle_reset(struct rq *rq, enum uclamp_id clamp_id,
if (!(rq->uclamp_flags & UCLAMP_FLAG_IDLE))
return;
WRITE_ONCE(rq->uclamp[clamp_id].value, clamp_value);
uclamp_rq_set(rq, clamp_id, clamp_value);
}
static inline
@@ -1158,8 +1158,8 @@ static inline void uclamp_rq_inc_id(struct rq *rq, struct task_struct *p,
if (bucket->tasks == 1 || uc_se->value > bucket->value)
bucket->value = uc_se->value;
if (uc_se->value > READ_ONCE(uc_rq->value))
WRITE_ONCE(uc_rq->value, uc_se->value);
if (uc_se->value > uclamp_rq_get(rq, clamp_id))
uclamp_rq_set(rq, clamp_id, uc_se->value);
}
/*
@@ -1225,7 +1225,7 @@ static inline void uclamp_rq_dec_id(struct rq *rq, struct task_struct *p,
if (likely(bucket->tasks))
return;
rq_clamp = READ_ONCE(uc_rq->value);
rq_clamp = uclamp_rq_get(rq, clamp_id);
/*
* Defensive programming: this should never happen. If it happens,
* e.g. due to future modification, warn and fixup the expected value.
@@ -1233,7 +1233,7 @@ static inline void uclamp_rq_dec_id(struct rq *rq, struct task_struct *p,
SCHED_WARN_ON(bucket->value > rq_clamp);
if (bucket->value >= rq_clamp) {
bkt_clamp = uclamp_rq_max_value(rq, clamp_id, uc_se->value);
WRITE_ONCE(uc_rq->value, bkt_clamp);
uclamp_rq_set(rq, clamp_id, bkt_clamp);
}
}