APAR status
Closed as program error.
Error description
A crash can occur when running the load balancer on AIX
Local fix
Problem summary
**************************************************************** * USERS AFFECTED: IBM WebSphere Application Server Load * * Balancer for IPv4 and IPv6 users * **************************************************************** * PROBLEM DESCRIPTION: This issue can only occur on the Load * * Balaner for IPv4 and IPv6 on AIX. A * * hang or crash occurs when LB is * * sending an ARP packet. * **************************************************************** * RECOMMENDATION: * **************************************************************** A crash can occur with a stack similar to : e_block_thread+000280 () soesend+00069C sosend+000014 .kernel_add_gate_cstack+000030 () os_packetxmit+000E1C lbarp_send+00099C _lbneigh_reply+0008C4 lbneigh_pbuf_entry+0003CC lbarp_entry+000B44 aix_recv+000234 Offsets may differ depending on code levels. This crash is more likely with multiple interfaces. The crash occur when LB is sending an ARP packet and an interrupt occurs, most likely from a packet received off a different interface. The interrupt processing triggers a context switch within the operating system kernel and the transmit API LB was using is not interrupt safe.
Problem conclusion
LB code was modified to change the API used to send ARP packets. The previous API (sosend) was not thread safe. Code was modified to use the interface output function which is thread safe. Fix packs containing fix: 8.5.5.18 9.0.5.4
Temporary fix
Minimize ARP as much as possible to avoid the problem. Use static ARP entries for HA partner, reach targets, MAC-based servers, etc. Gratuitous ARP on takeovers could still trigger issue even with static ARP entries.
Comments
APAR Information
APAR number
PH22784
Reported component name
WS EDGE LB IPV4
Reported component ID
5724H8812
Reported release
850
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt / Xsystem
Submitted date
2020-03-02
Closed date
2020-03-04
Last modified date
2020-06-30
APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:
Fix information
Fixed component name
WS EDGE LB IPV4
Fixed component ID
5724H8812
Applicable component levels
[{"Business Unit":{"code":"BU053","label":"Cloud & Data Platform"},"Product":{"code":"SSEQTP","label":"WebSphere Application Server"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"8.5","Line of Business":{"code":"LOB45","label":"Automation"}}]
Document Information
Modified date:
01 July 2020