1. 12 12月, 2011 2 次提交
    • F
      nohz: Allow rcu extended quiescent state handling seperately from tick stop · 2bbb6817
      Frederic Weisbecker 提交于
      It is assumed that rcu won't be used once we switch to tickless
      mode and until we restart the tick. However this is not always
      true, as in x86-64 where we dereference the idle notifiers after
      the tick is stopped.
      
      To prepare for fixing this, add two new APIs:
      tick_nohz_idle_enter_norcu() and tick_nohz_idle_exit_norcu().
      
      If no use of RCU is made in the idle loop between
      tick_nohz_enter_idle() and tick_nohz_exit_idle() calls, the arch
      must instead call the new *_norcu() version such that the arch doesn't
      need to call rcu_idle_enter() and rcu_idle_exit().
      
      Otherwise the arch must call tick_nohz_enter_idle() and
      tick_nohz_exit_idle() and also call explicitly:
      
      - rcu_idle_enter() after its last use of RCU before the CPU is put
      to sleep.
      - rcu_idle_exit() before the first use of RCU after the CPU is woken
      up.
      Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
      Cc: Mike Frysinger <vapier@gentoo.org>
      Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
      Cc: David Miller <davem@davemloft.net>
      Cc: Chris Metcalf <cmetcalf@tilera.com>
      Cc: Hans-Christian Egtvedt <hans-christian.egtvedt@atmel.com>
      Cc: Ralf Baechle <ralf@linux-mips.org>
      Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Russell King <linux@arm.linux.org.uk>
      Cc: Paul Mackerras <paulus@samba.org>
      Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
      Cc: Paul Mundt <lethal@linux-sh.org>
      Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      2bbb6817
    • F
      nohz: Separate out irq exit and idle loop dyntick logic · 280f0677
      Frederic Weisbecker 提交于
      The tick_nohz_stop_sched_tick() function, which tries to delay
      the next timer tick as long as possible, can be called from two
      places:
      
      - From the idle loop to start the dytick idle mode
      - From interrupt exit if we have interrupted the dyntick
      idle mode, so that we reprogram the next tick event in
      case the irq changed some internal state that requires this
      action.
      
      There are only few minor differences between both that
      are handled by that function, driven by the ts->inidle
      cpu variable and the inidle parameter. The whole guarantees
      that we only update the dyntick mode on irq exit if we actually
      interrupted the dyntick idle mode, and that we enter in RCU extended
      quiescent state from idle loop entry only.
      
      Split this function into:
      
      - tick_nohz_idle_enter(), which sets ts->inidle to 1, enters
      dynticks idle mode unconditionally if it can, and enters into RCU
      extended quiescent state.
      
      - tick_nohz_irq_exit() which only updates the dynticks idle mode
      when ts->inidle is set (ie: if tick_nohz_idle_enter() has been called).
      
      To maintain symmetry, tick_nohz_restart_sched_tick() has been renamed
      into tick_nohz_idle_exit().
      
      This simplifies the code and micro-optimize the irq exit path (no need
      for local_irq_save there). This also prepares for the split between
      dynticks and rcu extended quiescent state logics. We'll need this split to
      further fix illegal uses of RCU in extended quiescent states in the idle
      loop.
      Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
      Cc: Mike Frysinger <vapier@gentoo.org>
      Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
      Cc: David Miller <davem@davemloft.net>
      Cc: Chris Metcalf <cmetcalf@tilera.com>
      Cc: Hans-Christian Egtvedt <hans-christian.egtvedt@atmel.com>
      Cc: Ralf Baechle <ralf@linux-mips.org>
      Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
      Cc: Ingo Molnar <mingo@redhat.com>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Russell King <linux@arm.linux.org.uk>
      Cc: Paul Mackerras <paulus@samba.org>
      Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
      Cc: Paul Mundt <lethal@linux-sh.org>
      Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
      280f0677
  2. 08 12月, 2011 1 次提交
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