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 04/17] sched_ext: Fix bypassed tasks looping on a host without SCX_CAP_ENQ
Date: Fri, 23 Oct 2026 09:08:21 -1000 [thread overview]
Message-ID: <6f2d7109b2e68b12157f94841f929249@kernel.org> (raw)
In-Reply-To: <sashiko-outbox-183085@kernel.org>
Hello,
On Fri, Oct 23, 2026 at 06:50:45PM +0000, sashiko-bot@kernel.org wrote:
> [Severity: Medium]
> Can a bypassed task consumed with SCX_ENQ_IMMED get left waiting on
> rq->scx.local_dsq without being reenqueued when dispatch_one() finishes with
> SCX_DSP_PREV?
...
> Should the check at has_tasks in dispatch_one() also trigger
> scx_schedule_reenq_local() when verdict == SCX_DSP_PREV and rq->scx.nr_immed
> is non-zero, such as checking (rq->scx.local_dsq.nr > 1 || verdict ==
> SCX_DSP_PREV) && rq->scx.nr_immed?
The only way to get there is the parent keeping prev after dispatching its
children. The suggested change looks harmless though. I'll follow up with
it as a separate patch.
Thanks.
--
tejun
next prev parent reply other threads:[~2026-10-23 19:08 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-23 17:55 [PATCHSET v3 sched_ext/for-7.4] sched_ext: Fix bypassed sub-scheduler tasks stalling when the host lacks caps Tejun Heo
2026-10-23 17:55 ` [PATCH 01/17] sched_ext: Pack scx_ent_flags' multi-bit fields at the top Tejun Heo
2026-10-23 17:55 ` [PATCH 02/17] sched_ext: Clear holding_cpu where the claim is confirmed Tejun Heo
2026-10-23 17:55 ` [PATCH 03/17] sched_ext: Fix bypassed tasks stranded by the reenqueue limit Tejun Heo
2026-10-23 17:55 ` [PATCH 04/17] sched_ext: Fix bypassed tasks looping on a host without SCX_CAP_ENQ Tejun Heo
2026-10-23 18:50 ` sashiko-bot
2026-10-23 19:08 ` Tejun Heo [this message]
2026-10-23 17:55 ` [PATCH 05/17] sched_ext: Move refill_task_slice_dfl() below apply_slice_vtime() Tejun Heo
2026-10-23 17:55 ` [PATCH 06/17] sched_ext: Fix rescue served time disagreeing with the slice under proxy execution Tejun Heo
2026-10-23 17:55 ` [PATCH 07/17] sched_ext: Restore a rescuee's slice after ops.stopping() Tejun Heo
2026-10-23 17:55 ` [PATCH 08/17] sched_ext: Fix a cpu idling with a runnable rescuee Tejun Heo
2026-10-23 17:56 ` [PATCH 09/17] sched_ext: Mark the rescue grant as a kernel slice with SCX_TASK_KERNEL_SLICE Tejun Heo
2026-10-23 17:56 ` [PATCH 10/17] sched_ext: Refuse extending a kernel slice Tejun Heo
2026-10-23 17:56 ` [PATCH 11/17] sched_ext: Fix a cpu idling after put_prev_task_scx() queues its task on the local DSQ Tejun Heo
2026-10-23 17:56 ` [PATCH 12/17] sched_ext: Expire prev's slice in dispatch_one() under bypass Tejun Heo
2026-10-23 17:56 ` [PATCH 13/17] sched_ext: Fix bypassed tasks stalling when the host lacks SCX_CAP_BASE Tejun Heo
2026-10-23 19:02 ` sashiko-bot
2026-10-23 20:06 ` Tejun Heo
2026-10-23 17:56 ` [PATCH 14/17] sched_ext: Fix the bypass load balancer stranding tasks on cpus where " Tejun Heo
2026-10-23 17:56 ` [PATCH 15/17] sched_ext: Factor out bypass_lb_move() and insert with the donor DSQ unlocked Tejun Heo
2026-10-23 17:56 ` [PATCH 16/17] sched_ext: Let the bypass load balancer move tasks homed on other cpus Tejun Heo
2026-10-23 17:56 ` [PATCH 17/17] sched_ext: Fix queued bypassed tasks stalling when the host loses SCX_CAP_BASE Tejun Heo
2026-10-25 15:47 ` Andrea Righi
2026-10-26 21:31 ` Tejun Heo
2026-10-23 20:06 ` [PATCH 18/17] sched_ext: Fix use-after-free of a NONE rescuee leaving sched_ext Tejun Heo
2026-10-23 20:06 ` [PATCH 19/17] sched_ext: Fix the stall watchdog blaming a bypassing owner for a stuck task Tejun Heo
2026-10-25 15:52 ` Andrea Righi
2026-10-26 21:31 ` Tejun Heo
2026-10-23 20:10 ` [PATCH 20/17] sched_ext: Fix a lone IMMED task waiting behind a kept prev Tejun Heo
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