Messages in this thread Patch in this message | | | From | Hao Jia <> | Subject | [PATCH v2] sched/core: Adapt WARN_DOUBLE_CLOCK machinery for core-sched | Date | Wed, 15 Feb 2023 15:39:27 +0800 |
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When sched_core_enabled(), we sometimes need to call update_rq_clock() to update the rq clock of sibling CPUs on the same core, before that we need to clear RQCF_UPDATED of rq->clock_update_flags to avoid the WARN_DOUBLE_CLOCK warning. Because at this time the rq->clock_update_flags of sibling CPUs may be RQCF_UPDATED. If sched_core_enabled(), we will get a core wide rq->lock, so at this point we can safely clear RQCF_UPDATED of rq->clock_update_flags of all CPUs on this core to avoid the WARN_DOUBLE_CLOCK warning.
We cannot clear rq->clock_update_flags of other cpus on the same core in rq_pin_lock(). Because in some functions, we will temporarily give up core wide rq->lock, and then use raw_spin_rq_lock() to obtain core wide rq->lock, such as newidle_balance() and _double_lock_balance().
Steps to reproduce: 1. Enable CONFIG_SCHED_DEBUG and CONFIG_SCHED_CORE when compiling the kernel 2. echo 1 > /sys/kernel/debug/clear_warn_once echo "WARN_DOUBLE_CLOCK" > /sys/kernel/debug/sched/features 3. Run the linux/tools/testing/selftests/sched/cs_prctl_test test
Signed-off-by: Hao Jia <jiahao.os@bytedance.com> --- - Adapt WARN_DOUBLE_CLOCK machinery for core-sched instead of clearing WARN_DOUBLE_CLOCK warning one by one. - Modify commit information [v1] https://lore.kernel.org/all/20221206070550.31763-1-jiahao.os@bytedance.com
kernel/sched/core.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index e838feb6adc5..16a33e5adb77 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -427,11 +427,27 @@ void sched_core_put(void) schedule_work(&_work); } +static inline void sched_core_rq_clock_clear_update(struct rq *rq) +{ +#ifdef CONFIG_SCHED_DEBUG + const struct cpumask *smt_mask; + int i; + + if (rq->core_enabled) { + smt_mask = cpu_smt_mask(rq->cpu); + for_each_cpu(i, smt_mask) { + if (rq->cpu != i) + cpu_rq(i)->clock_update_flags &= (RQCF_REQ_SKIP|RQCF_ACT_SKIP); + } + } +#endif +} #else /* !CONFIG_SCHED_CORE */ static inline void sched_core_enqueue(struct rq *rq, struct task_struct *p) { } static inline void sched_core_dequeue(struct rq *rq, struct task_struct *p, int flags) { } +static inline void sched_core_rq_clock_clear_update(struct rq *rq) { } #endif /* CONFIG_SCHED_CORE */ @@ -546,6 +562,7 @@ void raw_spin_rq_lock_nested(struct rq *rq, int subclass) if (likely(lock == __rq_lockp(rq))) { /* preempt_count *MUST* be > 1 */ preempt_enable_no_resched(); + sched_core_rq_clock_clear_update(rq); return; } raw_spin_unlock(lock); -- 2.37.0 (Apple Git-136)
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