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  1. Couchbase Server
  2. MB-47760

[BP 7.0.2 MB-47749] - handleIndexMergeSnapshot() panic from extraneous s.muSnap.Unlock() calls

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    Description

      secondary/indexer/storage_manager.go handleIndexMergeSnapshot() does not lock, and its caller does not hold, the s.muSnap mutex (apparently it used to lock this at the top), but it still contains rarely-entered error reporting code blocks that unlock this mutex. If one of these error blocks gets entered, it triggers a panic.

      The fix is to delete the s.muSnap.Unlock() calls from this method. There are three of them (one is in commented-out code and two are in live code).
       

      Seen in currently undelivered new version of set14_rebalance_test.go TestFailoverAndRebalance:
      http://ci2i-unstable.northscale.in/gsi-04.08.2021-09.40.fail.html

      fatal error: sync: unlock of unlocked mutex
       
      goroutine 166 [running]:
      runtime.throw(0x131592e, 0x1e)
              /home/buildbot/.cbdepscache/exploded/x86_64/go-1.16.5/go/src/runtime/panic.go:1117 +0x72 fp=0xc006507ba0 sp=0xc006507b70 pc=0x43fdd2
      sync.throw(0x131592e, 0x1e)
              /home/buildbot/.cbdepscache/exploded/x86_64/go-1.16.5/go/src/runtime/panic.go:1103 +0x35 fp=0xc006507bc0 sp=0xc006507ba0 pc=0x474375
      sync.(*Mutex).unlockSlow(0xc004e96610, 0xffffffff)
              /home/buildbot/.cbdepscache/exploded/x86_64/go-1.16.5/go/src/sync/mutex.go:196 +0xd8 fp=0xc006507be8 sp=0xc006507bc0 pc=0x491e18
       
       
      Unlock call that panicked:
       
      sync.(*Mutex).Unlock(...)
              /home/buildbot/.cbdepscache/exploded/x86_64/go-1.16.5/go/src/sync/mutex.go:190
       
       
      Caused by s.muSnap.Unlock() in handleIndexMergeSnapshot (storage_manager.go:1720):
       
      github.com/couchbase/indexing/secondary/indexer.(*storageMgr).handleIndexMergeSnapshot(0xc004e96580, 0x14a4a80, 0xc00cdd0ff0)
              /opt/build/goproj/src/github.com/couchbase/indexing/secondary/indexer/storage_manager.go:1720 +0x699 fp=0xc006507f20 sp=0xc006507be8 pc=0xfb67f9
       
       
      github.com/couchbase/indexing/secondary/indexer.(*storageMgr).handleSupvervisorCommands(0xc004e96580, 0x14a4a80, 0xc00cdd0ff0)
              /opt/build/goproj/src/github.com/couchbase/indexing/secondary/indexer/storage_manager.go:224 +0x1b2 fp=0xc006507f58 sp=0xc006507f20 pc=0xfab8f2
      github.com/couchbase/indexing/secondary/indexer.(*storageMgr).run(0xc004e96580)
              /opt/build/goproj/src/github.com/couchbase/indexing/secondary/indexer/storage_manager.go:182 +0x48 fp=0xc006507fd8 sp=0xc006507f58 pc=0xfab628
      runtime.goexit()
              /home/buildbot/.cbdepscache/exploded/x86_64/go-1.16.5/go/src/runtime/asm_amd64.s:1371 +0x1 fp=0xc006507fe0 sp=0xc006507fd8 pc=0x4792e1
      created by github.com/couchbase/indexing/secondary/indexer.NewStorageManager
              /opt/build/goproj/src/github.com/couchbase/indexing/secondary/indexer/storage_manager.go:157 +0x2e5
      

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              kevin.cherkauer Kevin Cherkauer
              jeelan.poola Jeelan Poola
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