IPMI driver may hang when two request are issued at the same time

Issue

• While two IPMI clients issuing the requests to IPMI driver at the same time, the deadlock situation may happen.
• This is because IPMI driver uses two different kinds of lock variables, smi_info->msg_lock & smi_info->si_lock and two requests from clients get one of these two locks and waits the other lock respectively in some situations.
• This is one of the typical deadlock case.
• This problem is already fixed in upstream kernels and RHEL6.4. In that fix , one of the two locks is eliminated because the structure of IPMI driver is changed so that its function works as a kernel thread.
• So, this deadlock never happens after the fix.
• The related part in the change log of RHEL6.4 is this.

 +- [char] ipmi: use a tasklet for handling received messages (Prarit 
  Bhargava) [890160]

• We want the same fix for the RHEL5.9 errata and RH5.10GA