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| author | Ran Xiaokai <ran.xiaokai@zte.com.cn> | 2023-10-17 12:09:53 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-11-28 20:19:36 +0300 |
| commit | 3073f6df783d9d75f7f69f73e16c7ef85d6cfb63 (patch) | |
| tree | 43960cf79bad845c608087fccd083b501b5aa343 /kernel/cpu.c | |
| parent | f6cc3d85cb80d79578b9616e3fc6ab8e8d9aaa55 (diff) | |
| download | linux-3073f6df783d9d75f7f69f73e16c7ef85d6cfb63.tar.xz | |
cpu/hotplug: Don't offline the last non-isolated CPU
[ Upstream commit 38685e2a0476127db766f81b1c06019ddc4c9ffa ]
If a system has isolated CPUs via the "isolcpus=" command line parameter,
then an attempt to offline the last housekeeping CPU will result in a
WARN_ON() when rebuilding the scheduler domains and a subsequent panic due
to and unhandled empty CPU mas in partition_sched_domains_locked().
cpuset_hotplug_workfn()
rebuild_sched_domains_locked()
ndoms = generate_sched_domains(&doms, &attr);
cpumask_and(doms[0], top_cpuset.effective_cpus, housekeeping_cpumask(HK_FLAG_DOMAIN));
Thus results in an empty CPU mask which triggers the warning and then the
subsequent crash:
WARNING: CPU: 4 PID: 80 at kernel/sched/topology.c:2366 build_sched_domains+0x120c/0x1408
Call trace:
build_sched_domains+0x120c/0x1408
partition_sched_domains_locked+0x234/0x880
rebuild_sched_domains_locked+0x37c/0x798
rebuild_sched_domains+0x30/0x58
cpuset_hotplug_workfn+0x2a8/0x930
Unable to handle kernel paging request at virtual address fffe80027ab37080
partition_sched_domains_locked+0x318/0x880
rebuild_sched_domains_locked+0x37c/0x798
Aside of the resulting crash, it does not make any sense to offline the last
last housekeeping CPU.
Prevent this by masking out the non-housekeeping CPUs when selecting a
target CPU for initiating the CPU unplug operation via the work queue.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/202310171709530660462@zte.com.cn
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'kernel/cpu.c')
| -rw-r--r-- | kernel/cpu.c | 11 |
1 files changed, 7 insertions, 4 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c index 1a189da3bdac..303cb0591b4b 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -1523,11 +1523,14 @@ static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target) /* * Ensure that the control task does not run on the to be offlined * CPU to prevent a deadlock against cfs_b->period_timer. + * Also keep at least one housekeeping cpu onlined to avoid generating + * an empty sched_domain span. */ - cpu = cpumask_any_but(cpu_online_mask, cpu); - if (cpu >= nr_cpu_ids) - return -EBUSY; - return work_on_cpu(cpu, __cpu_down_maps_locked, &work); + for_each_cpu_and(cpu, cpu_online_mask, housekeeping_cpumask(HK_TYPE_DOMAIN)) { + if (cpu != work.cpu) + return work_on_cpu(cpu, __cpu_down_maps_locked, &work); + } + return -EBUSY; } static int cpu_down(unsigned int cpu, enum cpuhp_state target) |