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Mon, 07 Sep 2026 07:06:33 -0700 (PDT) Date: Mon, 7 Sep 2026 16:06:31 +0200 From: Michal =?utf-8?Q?Koutn=C3=BD?= To: Zhe Liu Cc: bsegall@google.com, cgroups@vger.kernel.org, corbet@lwn.net, dietmar.eggemann@arm.com, hannes@cmpxchg.org, juri.lelli@redhat.com, kprateek.nayak@amd.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, mgorman@suse.de, mingo@redhat.com, peterz@infradead.org, rostedt@goodmis.org, skhan@linuxfoundation.org, tj@kernel.org, vincent.guittot@linaro.org, vschneid@redhat.com, stable@vger.kernel.org Subject: Re: [PATCH v2 1/3] sched/fair: Remove the write-order dependency between cpu.max and cpu.max.burst Message-ID: References: <20260904062013.504236-1-liuzhe1@kylinos.cn> <20260904062013.504236-2-liuzhe1@kylinos.cn> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="5sahav5mzexczfrn" Content-Disposition: inline In-Reply-To: <20260904062013.504236-2-liuzhe1@kylinos.cn> --5sahav5mzexczfrn Content-Type: text/plain; protected-headers=v1; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [PATCH v2 1/3] sched/fair: Remove the write-order dependency between cpu.max and cpu.max.burst MIME-Version: 1.0 On Fri, Sep 04, 2026 at 02:20:11PM +0800, Zhe Liu wrot= e: > Keep the configured burst independent of the current quota and cap it > when CFS refills runtime. This allows quota and burst updates in either > order. >=20 > Fixes: f4183717b370 ("sched/fair: Introduce the burstable CFS controller") >=20 > Cc: stable@vger.kernel.org The change makes sense to me and it should've been like that from the beginning. OTOH, it may break someone's setup, so I'd take it but revert it should regressions be reported. Hence, I wouldn't mark it for stable.=20 > Signed-off-by: Zhe Liu > --- > kernel/sched/core.c | 3 +-- > kernel/sched/fair.c | 3 ++- > 2 files changed, 3 insertions(+), 3 deletions(-) >=20 > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index f78275192036..5269b8cfcf7f 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -10159,8 +10159,7 @@ static int tg_set_bandwidth(struct task_group *tg, > if (quota_us !=3D RUNTIME_INF && quota_us > max_bw_runtime_us) > return -EINVAL; > =20 > - if (quota_us !=3D RUNTIME_INF && (burst_us > quota_us || > - burst_us + quota_us > max_bw_runtime_us)) > + if (burst_us > max_bw_runtime_us) > return -EINVAL; I notice this'd be relaxed rather like: if (burst_us > max_bw_runtime_us / 2) return -EINVAL; I don't see in the current code that these BW_SHIFT'd calculations were relevant for burst. (Sashiko mentions overflows of the addition but I think it's confused MAX_BW and UULONG_MAX or more precisely (UULONG_MAX / NSEC_PER_USEC),) so even your version should still be safe. (Without that stable annotation above.) Reviewed-by: Michal Koutn=FD --5sahav5mzexczfrn Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iJEEABYKADkWIQRCE24Fn/AcRjnLivR+PQLnlNv4CAUCap7E4hsUgAAAAAAEAA5t YW51MiwyLjUrMS4xMiwyLDIACgkQfj0C55Tb+AgafAEA/lDIyfoaL+fSg3OpnbzT kKX5pkBVfO+FBzeCudKKlY0A/jVSRzj8PL3weJy/l9NmUY9jh/ilifk5nRv6Z0tK K/cK =kYvk -----END PGP SIGNATURE----- --5sahav5mzexczfrn--