IJ49587: DEADLOCK RELATED TO RETRIEVING NFSV4 ACL WITH LONG WAITER MESSAGE ?WAITING FOR EXCLUSIVE NF THSXLOCK FOR READERS TO FINISH

APAR status

• Closed as program error.

Error description

• When building an NFSv4 ACL from a POSIX access and default ACL
  of a directory, in between the retrievals of the access ACL and
  the default ACL, if an update or store ACL to another file or a
  directory happens, a deadlock can occur and the long waiter
  message ?waiting for exclusive NF ThSXLock for readers to
  finish? is seen.
  

Local fix

• - If NFSv4 ACL is needed, use NFSv4 ACL as the native ACL
  instead of using POSIX ACL, or
  - Avoid retrieving ACLs of directories as NFSv4 ACLs when their
  native version are POSIX,
  or
  - Use mode bits instead of ACLs.
  

Problem summary

• When building an NFSv4 ACL from a POSIX access and default ACL
  of a directory, in between the retrievals of the access ACL and
  the default ACL, if an update or store ACL to another file or a
  directory happens, a deadlock can occur and the long waiter
  message ?waiting for exclusive NF ThSXLock for readers to
  finish? is seen.
  

Problem conclusion

• This problem is fixed in 5.1.9.2
  To see all Spectrum Scale APARs and their respective
  Fix solutions refer to page:
  https://public.dhe.ibm.com/storage/spectrumscale/spectrum_scale_
  apars.html
  
  Benefits of the solution:
  Fixed the code so that the deadlock is avoided in this
  situation.
  
  Work Around:
  - If NFSv4 ACL is needed, use NFSv4 ACL as the native ACL
  instead of using POSIX ACL, or
  - Avoid retrieving ACLs of directories as NFSv4 ACLs when their
  native version are POSIX, or
  - Use mode bits instead of ACLs.
  
  Problem trigger:
  - Have directories with POSIX access and default ACL- Retrieve
  the NFSv4 ACL of the directories- At the same time, store or
  update the ACLs of other files/directories- If the store/update
  occurs in between the retrieval of the access ACL and the
  default ACL during the process of building the NFSv4 ACL, the
  deadlock will be hit.
  
  Symptom:
  Hang/Deadlock/Unresponsiveness/Long Waiters
  
  Platforms affected:
  Linux
  
  Functional Area affected:
  All Scale Users
  
  Customer Impact:
  High Importance
  

Temporary fix

Comments

APAR Information

• 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

  SPEC SCALE STD

• Fixed component ID

  5737F33AP

Applicable component levels