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  r4994 | marko | 2009-05-14 15:04:55 +0300 (Thu, 14 May 2009) | 18 lines

  branches/5.1: Prevent a race condition in innobase_commit() by ensuring
  that innodb_commit_concurrency>0 remains constant at run time. (Bug #42101)

  srv_commit_concurrency: Make this a static variable in ha_innodb.cc.

  innobase_commit_concurrency_validate(): Check that innodb_commit_concurrency
  is not changed from or to 0 at run time.  This is needed, because
  innobase_commit() assumes that innodb_commit_concurrency>0 remains constant.
  Without this limitation, the checks for innodb_commit_concurrency>0
  in innobase_commit() should be removed and that function would have to
  acquire and release commit_cond_m at least twice per invocation.
  Normally, innodb_commit_concurrency=0, and introducing the mutex operations
  would mean significant overhead.

  innodb_bug42101.test, innodb_bug42101-nonzero.test: Test cases.

  rb://123 approved by Heikki Tuuri
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