CASA6

• 

  Rui Xue <rx.astro@gmail.com> 01 Apr 2026 63a325ea22ef235dbdf4cc525f9b6cdf1e3203c3

  CAS-14756: Fix AutoLocking and `FilebufIO::readBlock` race condition in MPI parallel I/O
  This commit addresses potential I/O serialization and metadata corruption
  issues encountered when multiple MPI workers concurrently write to shared
  image cubes during the major cycle.
  
  Two primary fixes are introduced:
  1. Replaced `AutoNoReadLocking` with `AutoLocking`: When `inspectInterval=1.0`
     was used with `AutoNoReadLocking`, workers were permitted to read `table.f0`
     metadata without an explicitly synchronized read lock. This caused race
     conditions where one worker's metadata rewrite over `table.f0` (a non-atomic
     write >4KB) would crash another worker attempting to open the table,
     triggering a `FilebufIO::readBlock` exception. `AutoLocking` ensures the
     opening phase explicitly acquires the read lock, guaranteeing a coherent state.
  
  2. Release file locks during exception sleeps: When a `FilebufIO::readBlock`
     exception *is* caught natively (requiring the 50ms re-attempt sleep cycle),
     `im=nullptr` is now instantly called. This manually destructs the `PagedImage`
     pointer and surrenders the process's write lock *before* triggering the sleep.
     Previously, the write lock was retained during the 50ms delay, which
     needlessly serialized all other parallel workers awaiting their flush cycle.
  
  This commit further reduces the risk of random filesystem collisions on
  table re-open while enabling maximal tile streaming parallelism across workers.

  • casatools/src/code/synthesis/ImagerObjects/CubeMajorCycleAlgorithm.cc (version 63a325ea22ef235dbdf4cc525f9b6cdf1e3203c3) (diffs)
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  Rui Xue <rx.astro@gmail.com> 31 Mar 2026 4b3bfca414918261df2401ecd4274572d83dbf8f

  CAS-14756: use AutoNoReadLocking(inspectInterval=1s) in writeBackToFullImage
  NoLocking was allowing concurrent table.dat_tmp→table.dat renames to race
  across MPI workers, causing "RegularFile::move error: No such file or
  directory" in rank N's PagedImage destructor (job on cvpost124, build-5).
  
  casacore's table.dat metadata file is always shared — even when tile data
  blocks are strictly disjoint. NoLocking is therefore not safe for concurrent
  writers.
  
  AutoNoReadLocking with the default inspectInterval=0 is safe (the write lock
  is held from first putSlice to flush), but autoRelease() becomes a no-op and
  the entire writeback is serialized across workers — identical throughput to
  UserLocking.
  
  Setting inspectInterval=1.0 activates periodic lock inspection: every ~1 s
  autoRelease() checks whether another worker wants the lock; if so it flushes
  table.dat and releases, then the waiting worker acquires. Tile data I/O
  interleaves across workers (disjoint blocks → no contention); only the brief
  table.dat rename is serialized per transfer.

  • casatools/src/code/synthesis/ImagerObjects/CubeMajorCycleAlgorithm.cc (version 4b3bfca414918261df2401ecd4274572d83dbf8f) (diffs)