[PATCH v2] x86, hotplug: fix llc shared map unreleased during cpu hotplug

Wanpeng Li
2014-07-22T08:05:13Z

[ 220.262093] BUG: unable to handle kernel NULL pointer dereference at 0000000000000004
[ 220.262104] IP: [<ffffffff810e7ac9>] find_busiest_group+0x2b9/0xa30
[ 220.262111] PGD 5a9d5067 PUD 13067 PMD 0
[ 220.262117] Oops: 0000 [#3] SMP
[...]
[ 220.262245] Call Trace:
[ 220.262252] [<ffffffff810e8396>] load_balance+0x156/0x980
[ 220.262259] [<ffffffff816eeffe>] ? _raw_spin_unlock_irqrestore+0x2e/0xa0
[ 220.262266] [<ffffffff810e9aa3>] idle_balance+0xe3/0x150
[ 220.262270] [<ffffffff816ec4e7>] __schedule+0x797/0x8d0
[ 220.262277] [<ffffffff816ec934>] schedule+0x24/0x70
[ 220.262283] [<ffffffff816e9cd9>] schedule_timeout+0x119/0x1f0
[ 220.262294] [<ffffffff810bb6e0>] ? lock_timer_base+0x70/0x70
[ 220.262301] [<ffffffff816e9dc9>] schedule_timeout_uninterruptible+0x19/0x20
[ 220.262308] [<ffffffff810bd3e8>] msleep+0x18/0x20
[ 220.262317] [<ffffffff813aa11a>] lock_device_hotplug_sysfs+0x2a/0x50
[ 220.262323] [<ffffffff813aa16e>] online_store+0x2e/0x80
[ 220.262358] [<ffffffff813a873b>] dev_attr_store+0x1b/0x20
[ 220.262366] [<ffffffff812292fd>] sysfs_write_file+0xdd/0x160
[ 220.262377] [<ffffffff811b7e78>] vfs_write+0xc8/0x170
[ 220.262384] [<ffffffff811b83ca>] SyS_write+0x5a/0xa0
[ 220.262388] [<ffffffff816f76b9>] system_call_fastpath+0x16/0x1b

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.

Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
---
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;
--
1.9.1