From: Peter Zijlstra <peterz@infradead.org>
To: Andrea Righi <arighi@nvidia.com>
Cc: Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Valentin Schneider <vschneid@redhat.com>,
K Prateek Nayak <kprateek.nayak@amd.com>,
Tejun Heo <tj@kernel.org>,
Patrick Bellasi <patrick.bellasi@arm.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] sched/deadline: Skip bandwidth accounting with SCHED_FLAG_KEEP_PARAMS
Date: Thu, 30 Jul 2026 12:04:57 +0200 [thread overview]
Message-ID: <20260730100457.GP49951@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20260730055631.2271580-1-arighi@nvidia.com>
On Thu, Jul 30, 2026 at 07:56:31AM +0200, Andrea Righi wrote:
> A sched_setattr() invocation targeting a non-deadline task can specify
> SCHED_DEADLINE together with SCHED_FLAG_KEEP_PARAMS. The flag prevents
> __sched_setscheduler() from applying the requested parameters or class,
> but deadline admission runs before the guarded update and immediately
> accounts the requested bandwidth in the root domain. Repeating the
> invocation can therefore consume bandwidth without creating a deadline
> task capable of releasing it.
>
> Skip deadline bandwidth admission when SCHED_FLAG_KEEP_PARAMS is set,
> since neither the deadline policy nor its parameters will change.
I'm thinking this should be fixed by simply not allowing KEEP_PARAM when
the policy changes, no?
next prev parent reply other threads:[~2026-07-30 10:05 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-30 5:50 [PATCH 0/2] sched: Fix SCHED_FLAG_KEEP_PARAMS side effects Andrea Righi
2026-07-30 5:50 ` [PATCH 1/2] sched: Skip class callbacks with SCHED_FLAG_KEEP_PARAMS Andrea Righi
2026-07-30 7:29 ` K Prateek Nayak
2026-07-30 8:57 ` Andrea Righi
2026-07-30 9:57 ` Peter Zijlstra
2026-07-30 11:42 ` Andrea Righi
2026-07-30 5:56 ` [PATCH 2/2] sched/deadline: Skip bandwidth accounting " Andrea Righi
2026-07-30 10:04 ` Peter Zijlstra [this message]
2026-07-30 9:32 ` [PATCH 0/2] sched: Fix SCHED_FLAG_KEEP_PARAMS side effects Peter Zijlstra
2026-07-30 9:52 ` Peter Zijlstra
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