From: Tejun Heo <tj@kernel.org>
To: sashiko-reviews@lists.linux.dev
Cc: sashiko-bot@kernel.org, sched-ext@lists.linux.dev
Subject: Re: [PATCH 06/14] sched_ext: Fix a cpu idling with a runnable rescuee
Date: Thu, 22 Oct 2026 14:03:32 -1000 [thread overview]
Message-ID: <f80c1546b3d2831782241fb613e5c3ec@kernel.org> (raw)
In-Reply-To: <sashiko-outbox-182079@kernel.org>
Hello,
On Thu, Oct 22, 2026 at 09:56:08PM +0000, sashiko-bot@kernel.org wrote:
> [Severity: Medium]
> Should the scx_rescue_keep() check in kernel/sched/ext/ext.c:dispatch_one()
> run before the SCX_EV_DISPATCH_KEEP_LAST check above it?
No. A rescuee which passes the keep-last test is on a CPU where its
scheduler holds SCX_CAP_BASE. Either the insert it was rescued for
lacked ENQ or PREEMPT, or BASE came back during the rescue. It can stay
on that CPU like any other task of its scheduler, so ending the rescue
and refilling a default slice is fine. The comment saying that the keep
above declined prev is wrong for this case and the next version fixes
both the comment and the description.
Thanks.
--
tejun
next prev parent reply other threads:[~2026-10-23 0:03 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-22 21:38 [PATCHSET sched_ext/for-7.4] sched_ext: Fix bypassed sub-scheduler tasks stalling when the host lacks caps Tejun Heo
2026-10-22 21:38 ` [PATCH 01/14] sched_ext: Pack scx_ent_flags' multi-bit fields at the top Tejun Heo
2026-10-22 21:38 ` [PATCH 02/14] sched_ext: Clear holding_cpu where the claim is confirmed Tejun Heo
2026-10-22 21:38 ` [PATCH 03/14] sched_ext: Fix bypassed tasks looping on a host without SCX_CAP_ENQ Tejun Heo
2026-10-22 22:04 ` sashiko-bot
2026-10-23 0:03 ` Tejun Heo
2026-10-22 21:38 ` [PATCH 04/14] sched_ext: Move refill_task_slice_dfl() below apply_slice_vtime() Tejun Heo
2026-10-22 21:38 ` [PATCH 05/14] sched_ext: Restore a rescuee's slice after ops.stopping() Tejun Heo
2026-10-22 21:38 ` [PATCH 06/14] sched_ext: Fix a cpu idling with a runnable rescuee Tejun Heo
2026-10-22 21:56 ` sashiko-bot
2026-10-23 0:03 ` Tejun Heo [this message]
2026-10-22 21:38 ` [PATCH 07/14] sched_ext: Mark the rescue grant as a kernel slice with SCX_TASK_KERNEL_SLICE Tejun Heo
2026-10-22 21:38 ` [PATCH 08/14] sched_ext: Refuse extending a kernel slice Tejun Heo
2026-10-22 21:38 ` [PATCH 09/14] sched_ext: Fix a cpu idling after put_prev_task_scx() queues its task on the local DSQ Tejun Heo
2026-10-22 21:38 ` [PATCH 10/14] sched_ext: Fix bypassed tasks stalling when the host lacks SCX_CAP_BASE Tejun Heo
2026-10-22 22:09 ` sashiko-bot
2026-10-23 0:03 ` Tejun Heo
2026-10-22 21:38 ` [PATCH 11/14] sched_ext: Fix the bypass load balancer stranding tasks on cpus where " Tejun Heo
2026-10-22 21:38 ` [PATCH 12/14] sched_ext: Factor out bypass_lb_move() and insert with the donor DSQ unlocked Tejun Heo
2026-10-22 21:38 ` [PATCH 13/14] sched_ext: Let the bypass load balancer move tasks homed on other cpus Tejun Heo
2026-10-22 21:38 ` [PATCH 14/14] sched_ext: Fix queued bypassed tasks stalling when the host loses SCX_CAP_BASE Tejun Heo
2026-10-22 22:04 ` sashiko-bot
2026-10-23 0:03 ` Tejun Heo
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