path: root/kernel/time
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authorFrederic Weisbecker <fweisbec@gmail.com>2013-03-26 23:47:24 +0100
committerFrederic Weisbecker <fweisbec@gmail.com>2013-04-19 13:54:04 +0200
commitd1e43fa5f8bb25f83a86a29f11fcfb57ed4d7566 (patch)
tree9eff00255c1061248b6aef2c8341ea527610150c /kernel/time
parent0453b435df0d69dd0d8c42eb9b3015aaf0d8a032 (diff)
nohz: Ensure full dynticks CPUs are RCU nocbs
We need full dynticks CPU to also be RCU nocb so that we don't have to keep the tick to handle RCU callbacks. Make sure the range passed to nohz_full= boot parameter is a subset of rcu_nocbs= The CPUs that fail to meet this requirement will be excluded from the nohz_full range. This is checked early in boot time, before any CPU has the opportunity to stop its tick. Suggested-by: Steven Rostedt <rostedt@goodmis.org> Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> 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: Kevin Hilman <khilman@linaro.org> Cc: Li Zhong <zhong@linux.vnet.ibm.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>
Diffstat (limited to 'kernel/time')
1 files changed, 16 insertions, 6 deletions
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 2bac5ea2c9a..d71a5f2bd7b 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -203,17 +203,27 @@ static int __cpuinit tick_nohz_cpu_down_callback(struct notifier_block *nfb,
static char __initdata nohz_full_buf[NR_CPUS + 1];
-static int __init init_tick_nohz_full(void)
+void __init tick_nohz_init(void)
- if (have_nohz_full_mask)
- cpu_notifier(tick_nohz_cpu_down_callback, 0);
+ int cpu;
+ if (!have_nohz_full_mask)
+ return;
+ cpu_notifier(tick_nohz_cpu_down_callback, 0);
+ /* Make sure full dynticks CPU are also RCU nocbs */
+ for_each_cpu(cpu, nohz_full_mask) {
+ if (!rcu_is_nocb_cpu(cpu)) {
+ pr_warning("NO_HZ: CPU %d is not RCU nocb: "
+ "cleared from nohz_full range", cpu);
+ cpumask_clear_cpu(cpu, nohz_full_mask);
+ }
+ }
cpulist_scnprintf(nohz_full_buf, sizeof(nohz_full_buf), nohz_full_mask);
pr_info("NO_HZ: Full dynticks CPUs: %s.\n", nohz_full_buf);
- return 0;
#define have_nohz_full_mask (0)