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X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: YpCv8FNba0D1WRkd1OrqmFPS4rs4q3xC/jlZ3+e8WzFJs9no6kenxz9rheIW+hChncij/PpJDa77qfTkFKM0dQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ1PR11MB6131 X-OriginatorOrg: intel.com Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023-03-13 at 14:57:59 +0800, Yicong Yang wrote: > From: Yicong Yang > > On load balance we didn't check whether the candidate task is migration > disabled or not, this may hit the WARN_ON in set_task_cpu() since the > migration disabled tasks are expected to run on their current CPU. > We've run into this case several times on our server: > > ------------[ cut here ]------------ > WARNING: CPU: 7 PID: 0 at kernel/sched/core.c:3115 set_task_cpu+0x188/0x240 > Modules linked in: hclgevf xt_CHECKSUM ipt_REJECT nf_reject_ipv4 <...snip> > CPU: 7 PID: 0 Comm: swapper/7 Kdump: loaded Tainted: G O 6.1.0-rc4+ #1 > Hardware name: Huawei TaiShan 2280 V2/BC82AMDC, BIOS 2280-V2 CS V5.B221.01 12/09/2021 > pstate: 604000c9 (nZCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--) > pc : set_task_cpu+0x188/0x240 > lr : load_balance+0x5d0/0xc60 > sp : ffff80000803bc70 > x29: ffff80000803bc70 x28: ffff004089e190e8 x27: ffff004089e19040 > x26: ffff007effcabc38 x25: 0000000000000000 x24: 0000000000000001 > x23: ffff80000803be84 x22: 000000000000000c x21: ffffb093e79e2a78 > x20: 000000000000000c x19: ffff004089e19040 x18: 0000000000000000 > x17: 0000000000001fad x16: 0000000000000030 x15: 0000000000000000 > x14: 0000000000000003 x13: 0000000000000000 x12: 0000000000000000 > x11: 0000000000000001 x10: 0000000000000400 x9 : ffffb093e4cee530 > x8 : 00000000fffffffe x7 : 0000000000ce168a x6 : 000000000000013e > x5 : 00000000ffffffe1 x4 : 0000000000000001 x3 : 0000000000000b2a > x2 : 0000000000000b2a x1 : ffffb093e6d6c510 x0 : 0000000000000001 > Call trace: > set_task_cpu+0x188/0x240 > load_balance+0x5d0/0xc60 > rebalance_domains+0x26c/0x380 > _nohz_idle_balance.isra.0+0x1e0/0x370 > run_rebalance_domains+0x6c/0x80 > __do_softirq+0x128/0x3d8 > ____do_softirq+0x18/0x24 > call_on_irq_stack+0x2c/0x38 > do_softirq_own_stack+0x24/0x3c > __irq_exit_rcu+0xcc/0xf4 > irq_exit_rcu+0x18/0x24 > el1_interrupt+0x4c/0xe4 > el1h_64_irq_handler+0x18/0x2c > el1h_64_irq+0x74/0x78 > arch_cpu_idle+0x18/0x4c > default_idle_call+0x58/0x194 > do_idle+0x244/0x2b0 > cpu_startup_entry+0x30/0x3c > secondary_start_kernel+0x14c/0x190 > __secondary_switched+0xb0/0xb4 > ---[ end trace 0000000000000000 ]--- > > Signed-off-by: Yicong Yang > --- > kernel/sched/fair.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 7a1b1f855b96..8fe767362d22 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -8433,6 +8433,10 @@ int can_migrate_task(struct task_struct *p, struct lb_env *env) > if (kthread_is_per_cpu(p)) > return 0; > > + /* Migration disabled tasks need to be kept on their running CPU. */ > + if (is_migration_disabled(p)) > + return 0; > + > if (!cpumask_test_cpu(env->dst_cpu, p->cpus_ptr)) { > int cpu; > > -- > 2.24.0 > Looks reasonable to me. Would it be possible to also update the comments at the beginning of can_migrate_task() starts with: "We do not migrate tasks that are:" Reviewed-by: Chen Yu thanks, Chenyu