• Frederic Weisbecker's avatar
    nohz: Allow rcu extended quiescent state handling seperately from tick stop · 2bbb6817
    Frederic Weisbecker authored
    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: default avatarFrederic 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: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
    2bbb6817
process.c 9.04 KB