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Cisco Bug: CSCum70178 - Datapath:Observing Deadlock in different DATAPATH threads

Last Modified

Jun 08, 2020

Products (1)

  • Cisco ASA 5500-X Series Firewalls

Known Affected Releases

100.8(38.102) 8.4(7.9) 9.1 9.1(4.5) 9.1(5)

Description (partial)

Symptom:
Cisco ASA working as a Failover Standby Unit, periodically reloads in thread name datapath.

Crash message could be like the following :

Deadlock in thread DATAPATH-9-2588, from: 
Traceback from thread DATAPATH-9-2588:
Test scenario was Multiple ftp Clients from Outside to single FTP Server on Inside, with 1K conn/sec rate

Conditions:
Cisco ASA 8.4 when configured as standby in a failover pair.
Reason problem is more evident on Standby could be that, as there isn't much work to do,
it is possible that multiple Cores to work on flow-time-out at the same time

As part of detaching a flow from host->h_tcp_eflow emb-flow-count is being decremeted
But this is being done for a paired_flow->host, while holding the flow->host lock

This can lead to dead-locck, in the following senario :
Core-1 :
Forward_flow->host_A host-lock was acquired  snp_host_detach_flow and invoke snp_flow_dec_host_tcp_eflow_counters
Reverse_flow->host_B  host-lock is attempt to acquire at snp_flow_dec_host_tcp_eflow_counters.

Core-2 :
Forward_flow->host_A  host-lock was acquired  snp_host_detach_flow and invoke snp_flow_dec_host_tcp_eflow_counters
Reverse_flow->host_B   host-lock is attempt to acquire at snp_flow_dec_host_tcp_eflow_counters.
</RootCause>
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