lkml.org 
[lkml]   [2013]   [Jan]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 23/33] nohz: Don't turn off the tick if rcu needs it
    Date
    If RCU is waiting for the current CPU to complete a grace
    period, don't turn off the tick. Unlike dynctik-idle, we
    are not necessarily going to enter into rcu extended quiescent
    state, so we may need to keep the tick to note current CPU's
    quiescent states.

    [added build fix from Zen Lin]

    CHECKME: OTOH we don't want to handle a locally started
    grace period, this should be offloaded for rcu_nocb CPUs.
    What we want is to be kicked if we stay dynticks in the kernel
    for too long (ie: to report a quiescent state).
    rcu_pending() is perhaps an overkill just for that.

    Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Alessio Igor Bogani <abogani@kernel.org>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Chris Metcalf <cmetcalf@tilera.com>
    Cc: Christoph Lameter <cl@linux.com>
    Cc: Geoff Levand <geoff@infradead.org>
    Cc: Gilad Ben Yossef <gilad@benyossef.com>
    Cc: Hakan Akkan <hakanakkan@gmail.com>
    Cc: Ingo Molnar <mingo@kernel.org>
    Cc: Li Zhong <zhong@linux.vnet.ibm.com>
    Cc: Namhyung Kim <namhyung.kim@lge.com>
    Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Steven Rostedt <rostedt@goodmis.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
    ---
    include/linux/rcupdate.h | 1 +
    kernel/rcutree.c | 3 +--
    kernel/time/tick-sched.c | 3 +++
    3 files changed, 5 insertions(+), 2 deletions(-)

    diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
    index 829312e..2ebadac 100644
    --- a/include/linux/rcupdate.h
    +++ b/include/linux/rcupdate.h
    @@ -211,6 +211,7 @@ static inline int rcu_preempt_depth(void)
    extern void rcu_sched_qs(int cpu);
    extern void rcu_bh_qs(int cpu);
    extern void rcu_check_callbacks(int cpu, int user);
    +extern int rcu_pending(int cpu);
    struct notifier_block;
    extern void rcu_idle_enter(void);
    extern void rcu_idle_exit(void);
    diff --git a/kernel/rcutree.c b/kernel/rcutree.c
    index e9e0ffa..6ba3e02 100644
    --- a/kernel/rcutree.c
    +++ b/kernel/rcutree.c
    @@ -232,7 +232,6 @@ module_param(jiffies_till_next_fqs, ulong, 0644);

    static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *));
    static void force_quiescent_state(struct rcu_state *rsp);
    -static int rcu_pending(int cpu);

    /*
    * Return the number of RCU-sched batches processed thus far for debug & stats.
    @@ -2521,7 +2520,7 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
    * by the current CPU, returning 1 if so. This function is part of the
    * RCU implementation; it is -not- an exported member of the RCU API.
    */
    -static int rcu_pending(int cpu)
    +int rcu_pending(int cpu)
    {
    struct rcu_state *rsp;

    diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
    index 805eded..743b021 100644
    --- a/kernel/time/tick-sched.c
    +++ b/kernel/time/tick-sched.c
    @@ -596,6 +596,9 @@ static bool can_stop_full_tick(int cpu)
    if (!rcu_is_nocb_cpu(cpu))
    return false;

    + if (rcu_pending(cpu))
    + return false;
    +
    return true;
    }
    #endif
    --
    1.7.5.4


    \
     
     \ /
      Last update: 2013-01-08 04:41    [W:4.207 / U:0.288 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site