From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: sashiko-reviews@lists.linux.dev
Cc: linux-rt-devel@lists.linux.dev, tj@kernel.org,
hannes@cmpxchg.org, mkoutny@suse.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 04/21] sched/deadline: Do not divide by zero active CPUs of a root domain
Date: Thu, 5 Nov 2026 14:11:06 -0500 [thread overview]
Message-ID: <399a3f4a-76f1-4cf1-913c-4200cb4ce44a@efficios.com> (raw)
In-Reply-To: <sashiko-outbox-198153@kernel.org>
On 2026-11-04 16:46, sashiko-bot@kernel.org wrote:
[...]
>
> [Severity: Medium]
> Can updating dl_b->total_bw when cpus == 0 (or on an inactive CPU) underflow
> or corrupt dl_b->total_bw in the paths mentioned in the commit message?
That write is refused in v3 while the CPU is inactive (patch 4). The inactive
timer path is closed by patches 10 and 14: a release after a rebuild takes
nothing, and otherwise comes from the root domain that counted the bandwidth.
With admission control off, sched_setattr() on a task asleep on an offline
CPU still counts in the default root domain, with no active CPU to spread
the change over; the guard is for that, and the record releases from the
same root domain.
Thanks,
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com
next prev parent reply other threads:[~2026-11-05 19:11 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-04 21:11 [PATCH v2 00/21] sched/deadline: bandwidth accounting fixes and selftests Mathieu Desnoyers
2026-11-04 21:11 ` [PATCH v2 01/21] sched: Reject SCHED_FLAG_KEEP_PARAMS before reserving deadline bandwidth Mathieu Desnoyers
2026-11-05 7:14 ` Juri Lelli
2026-11-04 21:11 ` [PATCH v2 02/21] sched: Refuse SCHED_FLAG_KEEP_PARAMS that would change the policy Mathieu Desnoyers
2026-11-05 7:15 ` Juri Lelli
2026-11-04 21:11 ` [PATCH v2 03/21] sched/deadline: Do not admit bandwidth for parameters that are kept Mathieu Desnoyers
2026-11-05 10:20 ` Juri Lelli
2026-11-04 21:11 ` [PATCH v2 04/21] sched/deadline: Do not divide by zero active CPUs of a root domain Mathieu Desnoyers
2026-11-04 21:46 ` sashiko-bot
2026-11-05 19:11 ` Mathieu Desnoyers [this message]
2026-11-05 10:53 ` Juri Lelli
2026-11-04 21:11 ` [PATCH v2 05/21] sched/deadline: Do not BUG() on a deadline task with no active CPU allowed Mathieu Desnoyers
2026-11-05 10:59 ` Juri Lelli
2026-11-04 21:11 ` [PATCH v2 06/21] sched/deadline: Do not lose a throttled task switched out and back Mathieu Desnoyers
2026-11-04 22:09 ` sashiko-bot
2026-11-05 14:48 ` Juri Lelli
2026-11-04 21:11 ` [PATCH v2 07/21] sched/deadline: Do not release a departing sleeper's bandwidth twice Mathieu Desnoyers
2026-11-04 22:15 ` sashiko-bot
2026-11-05 19:11 ` Mathieu Desnoyers
2026-11-04 21:11 ` [PATCH v2 08/21] selftests/sched: Add a test of SCHED_DEADLINE policy round trips Mathieu Desnoyers
2026-11-05 15:00 ` Juri Lelli
2026-11-04 21:11 ` [PATCH v2 09/21] sched/deadline: Keep departing bandwidth across a root domain rebuild Mathieu Desnoyers
2026-11-04 22:44 ` sashiko-bot
2026-11-05 19:11 ` Mathieu Desnoyers
2026-11-04 21:11 ` [PATCH v2 10/21] selftests/sched: Test SCHED_DEADLINE " Mathieu Desnoyers
2026-11-04 21:11 ` [PATCH v2 11/21] sched/deadline: Do not take a waking task's bandwidth off a runqueue it left Mathieu Desnoyers
2026-11-04 21:11 ` [PATCH v2 12/21] sched/debug: Show the deadline bandwidth of each runqueue Mathieu Desnoyers
2026-11-04 21:11 ` [PATCH v2 13/21] sched/deadline: Rebuild the root domains' accounting without cpusets too Mathieu Desnoyers
2026-11-04 23:18 ` sashiko-bot
2026-11-04 21:12 ` [PATCH v2 14/21] selftests/sched: Add a test of SCHED_DEADLINE bandwidth accounting Mathieu Desnoyers
2026-11-04 21:12 ` [PATCH v2 15/21] sched/deadline: Record the root domain holding a task's bandwidth Mathieu Desnoyers
2026-11-04 23:31 ` sashiko-bot
2026-11-05 19:11 ` Mathieu Desnoyers
2026-11-04 21:12 ` [PATCH v2 16/21] sched/deadline: Move a task's bandwidth only where room was made Mathieu Desnoyers
2026-11-04 21:12 ` [PATCH v2 17/21] cgroup/cpuset: Give back the bandwidth an attach did not move Mathieu Desnoyers
2026-11-04 23:56 ` sashiko-bot
2026-11-04 21:12 ` [PATCH v2 18/21] sched/deadline: Credit a rebuild to a CPU that can hold the bandwidth Mathieu Desnoyers
2026-11-05 0:18 ` sashiko-bot
2026-11-04 21:12 ` [PATCH v2 19/21] sched: Clear cpuset_locked where the policy check retries Mathieu Desnoyers
2026-11-05 16:43 ` Andrea Parri
2026-11-05 17:08 ` Mathieu Desnoyers
2026-11-05 17:28 ` Andrea Parri
2026-11-04 21:12 ` [PATCH v2 20/21] sched/deadline: Cancel the replenishment timer with the parameters Mathieu Desnoyers
2026-11-05 0:25 ` sashiko-bot
2026-11-04 21:12 ` [PATCH v2 21/21] sched/deadline: Count the bandwidth a boosted task is given Mathieu Desnoyers
2026-11-05 0:36 ` sashiko-bot
[not found] ` <CGME20261105111941eucas1p1b50e9720b000ca86204aff3977c9fcbb@eucas1p1.samsung.com>
2026-11-05 11:19 ` [PATCH v2 00/21] sched/deadline: bandwidth accounting fixes and selftests Marek Szyprowski
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