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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Tue, 3 Jul 2007 17:42:37 +0000 (UTC)
To: src-committers@FreeBSD.org, cvs-src@FreeBSD.org, cvs-all@FreeBSD.org
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Cc: 
Subject: cvs commit: src/sys/fs/devfs devfs_int.h devfs_vnops.c
 src/sys/kern kern_conf.c src/sys/sys conf.h
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kib         2007-07-03 17:42:37 UTC

  FreeBSD src repository

  Modified files:
    sys/fs/devfs         devfs_int.h devfs_vnops.c 
    sys/kern             kern_conf.c 
    sys/sys              conf.h 
  Log:
  Since rev. 1.199 of sys/kern/kern_conf.c, the thread that calls
  destroy_dev() from d_close() cdev method would self-deadlock.
  devfs_close() bump device thread reference counter, and destroy_dev()
  sleeps, waiting for si_threadcount to reach zero for cdev without
  d_purge method.
  
  destroy_dev_sched() could be used instead from d_close(), to
  schedule execution of destroy_dev() in another context. The
  destroy_dev_sched_drain() function can be used to drain the scheduled
  calls to destroy_dev_sched(). Similarly, drain_dev_clone_events() drains
  the events clone to make sure no lingering devices are left after
  dev_clone event handler deregistered.
  
  make_dev_credf(MAKEDEV_REF) function should be used from dev_clone
  event handlers instead of make_dev()/make_dev_cred() to ensure that created
  device has reference counter bumped before cdev mutex is dropped inside
  make_dev().
  
  Reviewed by:    tegge (early versions), njl (programming interface)
  Debugging help and testing by:  Peter Holm
  Approved by:    re (kensmith)
  
  Revision  Changes    Path
  1.4       +6 -0      src/sys/fs/devfs/devfs_int.h
  1.148     +13 -0     src/sys/fs/devfs/devfs_vnops.c
  1.204     +147 -18   src/sys/kern/kern_conf.c
  1.233     +10 -0     src/sys/sys/conf.h