IJ49856: LONG WAITER - FILEBLOCKWRITEFETCHHANDLERTHREAD

APAR status

• Closed as program error.

Error description

• deadlock may appear
  
  FileBlockWriteFetchHandlerThread:
  (FetchFlowControlCondvar), reason 'wait for buffer for
  fetch'
  
  node is deadlocked to itself
  
  Benefits of the solution:
  
  Avoid unexpected long waiter that could occur during
  fetch by
  ensure a working writebehind thread if there are buffers
  on
  writebehind list.
  
  Work Around:
  
  
  Problem trigger:
  
  using desired prefetch threads instead of actual number
  of prefetch threads when determine if we still have
  threads available for writebehind.
  The internal dump showed the number of prefetch threads
  is less than desired
  number of prefetch threads which would cause making wrong
  decision
  
  
   Symptom:
  Hang/Deadlock/Unresponsiveness/LongWaiters
  
  Platforms affected:
  ALL Operating System environments
  
  Functional Area affected:
  All Scale Users
  
  Customer Impact:
  Critical
  
  Reported in:
  
  Storage Scale 5.1.8-2 , 5.1.9-0 , 5.1.9-1
  

Local fix

Problem summary

• Unexpected long waiter could appear with fetch thread waiting on
  FetchFlowControlCondvar with reason 'wait for buffer for
  fetch'.   This could happen workload caused all
  prefetch/writebehind threads are assigned to do prefetching.
  

Problem conclusion

• This problem is fixed in 5.1.9.3
  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:
  Prevent all prefetch/writebehind threads been assigned to do
  prefetch which can lead to deadlock/long waiter.
  
  Work Around:
  Avoid concurrently read/write to same file from multiple
  process.
  
  Problem trigger:
  Multiple application perform read/write to the same file at the
  same time.
  
  Symptom:
  Hang/Deadlock/Unresponsiveness/Long Waiters
  
  Platforms affected:
  ALL Operating System environments
  
  Functional Area affected:
  All Scale Users
  
  Customer Impact:
  Critical
  

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 DME

• Fixed component ID

  5737F34AP

Applicable component levels