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Wysocki" , Joel Granados , Thomas Gleixner Subject: [RFC 2/3] kernel/cpu: Mark nonboot cpus as inactive when shutting down nonboot cpus Date: Wed, 22 Oct 2025 20:13:44 +0800 Message-ID: <20251022121345.23496-3-piliu@redhat.com> In-Reply-To: <20251022121345.23496-1-piliu@redhat.com> References: <20251022121345.23496-1-piliu@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Content-Type: text/plain; charset="utf-8" The previous patch lifted the deadline bandwidth check during the kexec process, which raises a potential issue: as the number of online CPUs decreases, DL tasks may be crowded onto a few CPUs, which may starve the CPU hotplug kthread. As a result, the hot-removal cannot proceed in practice. On the other hand, as CPUs are offlined one by one, all tasks will eventually be migrated to the kexec CPU. Therefore, this patch marks all other CPUs as inactive to signal the scheduler to migrate tasks to the kexec CPU during hot-removal. Signed-off-by: Pingfan Liu Cc: Waiman Long Cc: Peter Zijlstra Cc: Juri Lelli Cc: Pierre Gondois Cc: Thomas Gleixner Cc: kexec@lists.infradead.org To: linux-kernel@vger.kernel.org --- kernel/cpu.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/kernel/cpu.c b/kernel/cpu.c index db9f6c539b28c..76aa0f784602b 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -1546,6 +1546,16 @@ void smp_shutdown_nonboot_cpus(unsigned int primary_= cpu) if (!cpu_online(primary_cpu)) primary_cpu =3D cpumask_first(cpu_online_mask); =20 + /* + * Mark all other CPUs as inactive so the scheduler won't select them as + * migration targets. + */ + for_each_online_cpu(cpu) { + if (cpu =3D=3D primary_cpu) + continue; + set_cpu_active(cpu, false); + } + for_each_online_cpu(cpu) { if (cpu =3D=3D primary_cpu) continue; --=20 2.49.0