From: David Vernet <void@manifault.com>
To: Tejun Heo <tj@kernel.org>
Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com,
schatzberg.dan@gmail.com
Subject: Re: [PATCH 2/2] sched_ext: Make scx_bpf_reenqueue_local() skip tasks that are being migrated
Date: Tue, 9 Jul 2024 17:16:48 -0500 [thread overview]
Message-ID: <20240709221648.GB248762@maniforge> (raw)
In-Reply-To: <20240709211001.1198145-3-tj@kernel.org>
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On Tue, Jul 09, 2024 at 11:09:43AM -1000, Tejun Heo wrote:
> When a running task is migrated to another CPU, the stop_task is used to
> preempt the running task and migrate it. This, expectedly, invokes
> ops.cpu_release(). If the BPF scheduler then calls
> scx_bpf_reenqueue_local(), it re-enqueues all tasks on the local DSQ
> including the task which is being migrated.
>
> This creates an unnecessary re-enqueue of a task which is about to be
> deactivated and re-activated for migration anyway. It can also cause
> confusion for the BPF scheduler as scx_bpf_task_cpu() of the task and its
> allowed CPUs may not agree while migration is pending.
>
> Signed-off-by: Tejun Heo <tj@kernel.org>
> Fixes: 245254f7081d ("sched_ext: Implement sched_ext_ops.cpu_acquire/release()")
> Cc: David Vernet <void@manifault.com>
Acked-by: David Vernet <void@manifault.com>
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next prev parent reply other threads:[~2024-07-09 22:16 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-07-09 21:09 [PATCHSET sched_ext/for-6.11] sched_ext: Fix scx_bpf_reenqueue_local() Tejun Heo
2024-07-09 21:09 ` [PATCH 1/2] sched_ext: Reimplement scx_bpf_reenqueue_local() Tejun Heo
2024-07-09 21:18 ` David Vernet
2024-07-09 21:09 ` [PATCH 2/2] sched_ext: Make scx_bpf_reenqueue_local() skip tasks that are being migrated Tejun Heo
2024-07-09 22:16 ` David Vernet [this message]
2024-07-09 22:31 ` [PATCHSET sched_ext/for-6.11] sched_ext: Fix scx_bpf_reenqueue_local() Tejun Heo
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