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From: Mitsuru IWASAKI <iwasaki@FreeBSD.org>
Date: Thu, 17 Oct 2002 06:55:44 -0700 (PDT)
To: cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject: cvs commit: src/sys/i386/isa clock.c
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iwasaki     2002/10/17 06:55:44 PDT

  Modified files:
    sys/i386/isa         clock.c 
  Log:
  1. Fix a comment.  Locking _is_ needed (but not done).
  2. Update a comment.  We now restore much more than RTC updates and
     interrupts.
  3. Order change.  Stop interrupts by writing to RTC_STATUSB,
     restore rate bits for the interrupts by writing to RTC_STATUSA,
     then enable interrupts again.
     This seems to be done perfectly backwards in startrtclock().
     Otherwise, the idea for this change was obtained from
     startrtclock().
  4. Don't stop the clock (RTCB_HALT).  We only program some control bits
     and don't want to stop the clock.
  5. (Not really related.)  Add caveats to the comment about timer_restore().
     The update is non-atomic since locking is not done.
  
  On locking:
  6. rtcin() and writertc() are locked() adequately by splhigh() in RELENG_4,
     but this locking is null in -current.
  7. Doing things in the correct order in (3) combined with (6) is probably
     enough locking for rtcrestore() in RELENG_4.  In -current, the
     writertc()'s race with rtcintr() unless the BIOS disables RTC interrupts.
  
  Submitted by:   bde (including commit message)
  MFC after:      1 week
  
  Revision  Changes    Path
  1.190     +8 -12     src/sys/i386/isa/clock.c

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