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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Fri, 12 Dec 2008 12:06:28 +0000 (UTC)
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Subject: cvs commit: src/sys/kern kern_prot.c kern_sysctl.c
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kib         2008-12-12 12:06:28 UTC

  FreeBSD src repository

  Modified files:
    sys/kern             kern_prot.c kern_sysctl.c 
  Log:
  SVN rev 185983 on 2008-12-12 12:06:28Z by kib
  
  The userland_sysctl() function retries sysctl_root() until returned
  error is not EAGAIN. Several sysctls that inspect another process use
  p_candebug() for checking access right for the curproc. p_candebug()
  returns EAGAIN for some reasons, in particular, for the process doing
  exec() now. If execing process tries to lock Giant, we get a livelock,
  because sysctl handlers are covered by Giant, and often do not sleep.
  
  Break the livelock by dropping Giant and allowing other threads to
  execute in the EAGAIN loop.
  
  Also, do not return EAGAIN from p_candebug() when process is executing,
  use more appropriate EBUSY error [1].
  
  Reported and tested by: pho
  Suggested by:   rwatson [1]
  Reviewed by:    rwatson, des
  MFC after:      1 week
  
  Revision  Changes    Path
  1.215     +1 -1      src/sys/kern/kern_prot.c
  1.181     +8 -2      src/sys/kern/kern_sysctl.c