cvs commit: src/sys/kern kern_condvar.c kern_mutex.c kern_synch.c subr_sleepqueue.c subr_turnstile.c src/sys/sys sleepqueue.h turnstile.h

[John Baldwin]

jhb         2004-10-12 18:36:20 UTC

  FreeBSD src repository

  Modified files:
    sys/kern             kern_condvar.c kern_mutex.c kern_synch.c 
                         subr_sleepqueue.c subr_turnstile.c 
    sys/sys              sleepqueue.h turnstile.h 
  Log:
  Refine the turnstile and sleep queue interfaces just a bit:
  - Add a new _lock() call to each API that locks the associated chain lock
    for a lock_object pointer or wait channel.  The _lookup() functions now
    require that the chain lock be locked via _lock() when they are called.
  - Change sleepq_add(), turnstile_wait() and turnstile_claim() to lookup
    the associated queue structure internally via _lookup() rather than
    accepting a pointer from the caller.  For turnstiles, this means that
    the actual lookup of the turnstile in the hash table is only done when
    the thread actually blocks rather than being done on each loop iteration
    in _mtx_lock_sleep().  For sleep queues, this means that sleepq_lookup()
    is no longer used outside of the sleep queue code except to implement an
    assertion in cv_destroy().
  - Change sleepq_broadcast() and sleepq_signal() to require that the chain
    lock is already required.  For condition variables, this lets the
    cv_broadcast() and cv_signal() functions lock the sleep queue chain lock
    while testing the waiters count.  This means that the waiters count
    internal to condition variables is no longer protected by the interlock
    mutex and cv_broadcast() and cv_signal() now no longer require that the
    interlock be held when they are called.  This lets consumers of condition
    variables drop the lock before waking other threads which can result in
    fewer context switches.
  
  MFC after:      1 month
  
  Revision  Changes    Path
  1.52      +16 -15    src/sys/kern/kern_condvar.c
  1.151     +4 -5      src/sys/kern/kern_mutex.c
  1.263     +4 -3      src/sys/kern/kern_synch.c
  1.13      +31 -14    src/sys/kern/subr_sleepqueue.c
  1.150     +34 -12    src/sys/kern/subr_turnstile.c
  1.5       +11 -12    src/sys/sys/sleepqueue.h
  1.5       +17 -16    src/sys/sys/turnstile.h