Ping Ingo, Peter Z, HPA, 于 14-9-17 下午3:17, Wanpeng Li 写道: > BUG: unable to handle kernel NULL pointer dereference at 0000000000000004 > IP: [..] find_busiest_group > PGD 5a9d5067 PUD 13067 PMD 0 > Oops: 0000 [#3] SMP > [...] > Call Trace: > load_balance > ? _raw_spin_unlock_irqrestore > idle_balance > __schedule > schedule > schedule_timeout > ? lock_timer_base > schedule_timeout_uninterruptible > msleep > lock_device_hotplug_sysfs > online_store > dev_attr_store > sysfs_write_file > vfs_write > SyS_write > system_call_fastpath > > This bug can be triggered by hot add and remove large number of xen > domain0's vcpus repeatedly. > > Last level cache shared map is built during cpu up and build sched domain > routine takes advantage of it to setup sched domain cpu topology, however, > llc shared map is unreleased during cpu disable which lead to invalid sched > domain cpu topology. This patch fix it by release llc shared map correctly > during cpu disable. > > Reviewed-by: Toshi Kani <toshi.k...@hp.com> > Reviewed-by: Yasuaki Ishimatsu <isimatu.yasu...@jp.fujitsu.com> > Tested-by: Linn Crosetto <l...@hp.com> > Signed-off-by: Wanpeng Li <wanpeng...@linux.intel.com> > --- > v4 -> v5: > * add the description when the bug can occur > v3 -> v4: > * simplify backtrace > v2 -> v3: > * simplify backtrace > v1 -> v2: > * fix subject line > > arch/x86/kernel/smpboot.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c > index 5492798..0134ec7 100644 > --- a/arch/x86/kernel/smpboot.c > +++ b/arch/x86/kernel/smpboot.c > @@ -1292,6 +1292,9 @@ static void remove_siblinginfo(int cpu) > > for_each_cpu(sibling, cpu_sibling_mask(cpu)) > cpumask_clear_cpu(cpu, cpu_sibling_mask(sibling)); > + for_each_cpu(sibling, cpu_llc_shared_mask(cpu)) > + cpumask_clear_cpu(cpu, cpu_llc_shared_mask(sibling)); > + cpumask_clear(cpu_llc_shared_mask(cpu)); > cpumask_clear(cpu_sibling_mask(cpu)); > cpumask_clear(cpu_core_mask(cpu)); > c->phys_proc_id = 0;
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