diff options
| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2013-06-21 20:10:40 -0400 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2013-08-31 17:44:02 -0400 |
| commit | eb75767be0e514f97bf1b5cec763696cfc7f7e2a (patch) | |
| tree | 08cae2878e46409d6f5cffd0d37499bfa4851abc /kernel/rcutree_plugin.h | |
| parent | 0edd1b1784cbdad55aca2c1293be018f53c0ab1d (diff) | |
nohz_full: Force RCU's grace-period kthreads onto timekeeping CPU
Because RCU's quiescent-state-forcing mechanism is used to drive the
full-system-idle state machine, and because this mechanism is executed
by RCU's grace-period kthreads, this commit forces these kthreads to
run on the timekeeping CPU (tick_do_timer_cpu). To do otherwise would
mean that the RCU grace-period kthreads would force the system into
non-idle state every time they drove the state machine, which would
be just a bit on the futile side.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Diffstat (limited to 'kernel/rcutree_plugin.h')
| -rw-r--r-- | kernel/rcutree_plugin.h | 21 |
1 files changed, 20 insertions, 1 deletions
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index 45ebba747af4..130c97b027f2 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h | |||
| @@ -2531,7 +2531,8 @@ static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle, | |||
| 2531 | if (!*isidle || rdp->rsp != rcu_sysidle_state || | 2531 | if (!*isidle || rdp->rsp != rcu_sysidle_state || |
| 2532 | cpu_is_offline(rdp->cpu) || rdp->cpu == tick_do_timer_cpu) | 2532 | cpu_is_offline(rdp->cpu) || rdp->cpu == tick_do_timer_cpu) |
| 2533 | return; | 2533 | return; |
| 2534 | /* WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu); */ | 2534 | if (rcu_gp_in_progress(rdp->rsp)) |
| 2535 | WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu); | ||
| 2535 | 2536 | ||
| 2536 | /* Pick up current idle and NMI-nesting counter and check. */ | 2537 | /* Pick up current idle and NMI-nesting counter and check. */ |
| 2537 | cur = atomic_read(&rdtp->dynticks_idle); | 2538 | cur = atomic_read(&rdtp->dynticks_idle); |
| @@ -2557,6 +2558,20 @@ static bool is_sysidle_rcu_state(struct rcu_state *rsp) | |||
| 2557 | } | 2558 | } |
| 2558 | 2559 | ||
| 2559 | /* | 2560 | /* |
| 2561 | * Bind the grace-period kthread for the sysidle flavor of RCU to the | ||
| 2562 | * timekeeping CPU. | ||
| 2563 | */ | ||
| 2564 | static void rcu_bind_gp_kthread(void) | ||
| 2565 | { | ||
| 2566 | int cpu = ACCESS_ONCE(tick_do_timer_cpu); | ||
| 2567 | |||
| 2568 | if (cpu < 0 || cpu >= nr_cpu_ids) | ||
| 2569 | return; | ||
| 2570 | if (raw_smp_processor_id() != cpu) | ||
| 2571 | set_cpus_allowed_ptr(current, cpumask_of(cpu)); | ||
| 2572 | } | ||
| 2573 | |||
| 2574 | /* | ||
| 2560 | * Return a delay in jiffies based on the number of CPUs, rcu_node | 2575 | * Return a delay in jiffies based on the number of CPUs, rcu_node |
| 2561 | * leaf fanout, and jiffies tick rate. The idea is to allow larger | 2576 | * leaf fanout, and jiffies tick rate. The idea is to allow larger |
| 2562 | * systems more time to transition to full-idle state in order to | 2577 | * systems more time to transition to full-idle state in order to |
| @@ -2766,6 +2781,10 @@ static bool is_sysidle_rcu_state(struct rcu_state *rsp) | |||
| 2766 | return false; | 2781 | return false; |
| 2767 | } | 2782 | } |
| 2768 | 2783 | ||
| 2784 | static void rcu_bind_gp_kthread(void) | ||
| 2785 | { | ||
| 2786 | } | ||
| 2787 | |||
| 2769 | static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle, | 2788 | static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle, |
| 2770 | unsigned long maxj) | 2789 | unsigned long maxj) |
| 2771 | { | 2790 | { |