@@ -35,6 +35,7 @@ extern int spinning_secondaries;
extern void cpu_die(void);
extern int cpu_to_chip_id(int cpu);
+DECLARE_PER_CPU(struct cpu, cpu_devices);
#ifdef CONFIG_SMP
struct smp_ops_t {
@@ -26,7 +26,7 @@
#include <asm/lppaca.h>
#endif
-static DEFINE_PER_CPU(struct cpu, cpu_devices);
+DEFINE_PER_CPU(struct cpu, cpu_devices);
/*
* SMT snooze delay stuff, 64-bit only for now
@@ -367,6 +367,7 @@ static int dlpar_online_cpu(struct device_node *dn)
cpu_maps_update_done();
timed_topology_update(1);
find_and_online_cpu_nid(cpu);
+ register_cpu(&per_cpu(cpu_devices, cpu), cpu);
rc = device_online(get_cpu_device(cpu));
if (rc)
goto out;
@@ -541,6 +542,8 @@ static int dlpar_offline_cpu(struct device_node *dn)
rc = device_offline(get_cpu_device(cpu));
if (rc)
goto out;
+ unregister_cpu(container_of(get_cpu_device(cpu),
+ struct cpu, dev));
cpu_maps_update_begin();
break;
Technically speaking, echo 1/0 > cpuX/online is only a subset of cpu hotplug/unplug, i.e. add/remove. The latter one includes the physical adding/removing of a cpu device. Some user space tools such as kexec-tools resort to the event add/remove to automatically rebuild dtb. If the dtb is not rebuilt correctly, we may hang on 2nd kernel due to lack the info of boot-cpu-hwid in dtb. The steps to trigger the bug: (suppose 8 threads/core) drmgr -c cpu -r -q 1 systemctl restart kdump.service drmgr -c cpu -a -q 1 taskset -c 11 sh -c "echo c > /proc/sysrq-trigger" Then, failure info: [ 205.299528] SysRq : Trigger a crash [ 205.299551] Unable to handle kernel paging request for data at address 0x00000000 [ 205.299558] Faulting instruction address: 0xc0000000006001a0 [ 205.299564] Oops: Kernel access of bad area, sig: 11 [#1] [ 205.299569] SMP NR_CPUS=2048 NUMA pSeries [ 205.299575] Modules linked in: macsec sctp_diag sctp tcp_diag udp_diag inet_diag unix_diag af_packet_diag netlink_diag ip6t_rpfilter ipt_REJECT nf_reject_ipv4 ip6t_REJECT nf_reject_ipv6 xt_conntrack ip_set nfnetlink ebtable_nat ebtable_broute bridge stp llc ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle ip6table_security ip6table_raw iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle iptable_security iptable_raw ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter xfs libcrc32c sg pseries_rng binfmt_misc ip_tables ext4 mbcache jbd2 sd_mod crc_t10dif crct10dif_generic crct10dif_common ibmvscsi scsi_transport_srp ibmveth scsi_tgt dm_mirror dm_region_hash dm_log dm_mod [ 205.299658] CPU: 11 PID: 2521 Comm: bash Not tainted 3.10.0-799.el7.ppc64le #1 [ 205.299664] task: c00000017bcd15e0 ti: c00000014f410000 task.ti: c00000014f410000 [ 205.299670] NIP: c0000000006001a0 LR: c000000000600ddc CTR: c000000000600180 [ 205.299676] REGS: c00000014f413a70 TRAP: 0300 Not tainted (3.10.0-799.el7.ppc64le) [ 205.299681] MSR: 8000000000009033 <SF,EE,ME,IR,DR,RI,LE> CR: 28222822 XER: 00000001 [ 205.299696] CFAR: c000000000009368 DAR: 0000000000000000 DSISR: 42000000 SOFTE: 1 GPR00: c000000000600dbc c00000014f413cf0 c000000001263200 0000000000000063 GPR04: c0000000019ca818 c0000000019db5f8 00000000000000c2 c00000000140aa30 GPR08: 0000000000000007 0000000000000001 0000000000000000 c00000000140fc60 GPR12: c000000000600180 c000000007b36300 0000000010139e58 0000000040000000 GPR16: 000000001013b5d0 0000000000000000 00000000101306fc 0000000010139de4 GPR20: 0000000010139de8 0000000010093150 0000000000000000 0000000000000000 GPR24: 000000001013b5e0 00000000100fa0e8 0000000000000007 c0000000011af1c8 GPR28: 0000000000000063 c0000000011af588 c000000001179ba8 0000000000000002 [ 205.299770] NIP [c0000000006001a0] sysrq_handle_crash+0x20/0x30 [ 205.299776] LR [c000000000600ddc] write_sysrq_trigger+0x10c/0x230 [ 205.299781] Call Trace: [ 205.299786] [c00000014f413cf0] [c000000000600dbc] write_sysrq_trigger+0xec/0x230 (unreliable) [ 205.299794] [c00000014f413d90] [c0000000003eb2c4] proc_reg_write+0x84/0x120 [ 205.299801] [c00000014f413dd0] [c000000000330a80] SyS_write+0x150/0x400 [ 205.299808] [c00000014f413e30] [c00000000000a184] system_call+0x38/0xb4 [ 205.299813] Instruction dump: [ 205.299816] 409effb8 7fc3f378 4bfff381 4bffffac 3c4c00c6 38423080 3d42fff1 394a6930 [ 205.299827] 39200001 912a0000 7c0004ac 39400000 <992a0000> 4e800020 60000000 60420000 [ 205.299838] ---[ end trace f590a5dbd3f63aab ]--- [ 205.301812] [ 205.301829] Sending IPI to other CPUs [ 205.302846] IPI complete I'm in purgatory -- > hang up here This patch uses the interface register_/unregister_cpu to fix the problem Signed-off-by: Pingfan Liu <kernelfans@gmail.com> Reported-by: Hari Bathini <hbathini@linux.vnet.ibm.com> Reviewed-by: Hari Bathini <hbathini@linux.vnet.ibm.com> --- arch/powerpc/include/asm/smp.h | 1 + arch/powerpc/kernel/sysfs.c | 2 +- arch/powerpc/platforms/pseries/hotplug-cpu.c | 3 +++ 3 files changed, 5 insertions(+), 1 deletion(-)