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From: KATO Takenori <kato@freefall.FreeBSD.ORG>
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	Mon, 28 Apr 1997 19:06:08 -0700 (PDT)
Date: Mon, 28 Apr 1997 19:06:08 -0700 (PDT)
Message-Id: <199704290206.TAA02655@freefall.freebsd.org>
To: CVS-committers@FreeBSD.org, cvs-all@FreeBSD.org, cvs-sys@FreeBSD.org
Subject: cvs commit:  src/sys/miscfs/union union_vnops.c
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kato        97/04/28 19:06:08

  Modified:    sys/miscfs/union  union_vnops.c
  Log:
  Revised fix for locking violation when unionfs calls vput with
  UN_KLOCK flag.
  
  When UN_KLOCK is set, VOP_UNLOCK should keep uppervp locked and clear
  UN_ULOCK flag.  To do this, when UN_KLOCK is set, (1) union_unlock
  clears UN_ULOCK and does not clear UN_KLOCK, (2) union_lock() does not
  access uppervp and does not clear UN_KLOCK, and (3) callers of
  vput/VOP_UNLOCK should clear UN_KLOCK.  For example, vput becomes:
  
  	SETKLOCK(union_node);
  	vput(vnode);
  	CLEARKLOCK(union_node);
  
  where SETKLOCK macro sets UN_KLOCK and CLEARKLOCK macro clears
  UN_KLOCK.
  
  Revision  Changes    Path
  1.31      +36 -32    src/sys/miscfs/union/union_vnops.c