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From: Attilio Rao <attilio@FreeBSD.org>
Date: Mon, 18 Jan 2010 14:43:44 +0000 (UTC)
To: cvs-src-old@freebsd.org
X-FreeBSD-CVS-Branch: RELENG_8
Subject: cvs commit: src/share/man/man9 sleepqueue.9 src/sys/kern
 kern_lock.c kern_sx.c subr_sleepqueue.c src/sys/sys lockmgr.h
 sleepqueue.h
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attilio     2010-01-18 14:43:44 UTC

  FreeBSD src repository

  Modified files:        (Branch: RELENG_8)
    share/man/man9       sleepqueue.9 
    sys/kern             kern_lock.c kern_sx.c subr_sleepqueue.c 
    sys/sys              lockmgr.h sleepqueue.h 
  Log:
  SVN rev 202576 on 2010-01-18 14:43:44Z by attilio
  
  MFC r200447,201703,201709-201710:
  In current code, threads performing an interruptible sleep
  will leave the waiters flag on forcing the owner to do a wakeup even
  when the waiter queue is empty.
  That operation may lead to a deadlock in the case of doing a fake wakeup
  on the "preferred" queue while the other queue has real waiters on it,
  because nobody is going to wakeup the 2nd queue waiters and they will
  sleep indefinitively.
  A similar bug, is present, for lockmgr in the case the waiters are
  sleeping with LK_SLEEPFAIL on.
  
  Add a sleepqueue interface which does report the actual number of waiters
  on a specified queue of a waitchannel and track if at least one sleepfail
  waiter is present or not. In presence of this or empty "preferred" queue,
  wakeup both waiters queues.
  
  Discussed with: kib
  Tested by:      Pete French <petefrench at ticketswitch dot com>,
                  Justin Head <justin at encarnate dot com>
  
  Revision   Changes    Path
  1.17.2.3   +12 -1     src/share/man/man9/sleepqueue.9
  1.144.2.7  +142 -15   src/sys/kern/kern_lock.c
  1.67.2.7   +5 -1      src/sys/kern/kern_sx.c
  1.64.2.2   +31 -4     src/sys/kern/subr_sleepqueue.c
  1.72.2.2   +3 -0      src/sys/sys/lockmgr.h
  1.17.2.2   +1 -0      src/sys/sys/sleepqueue.h