Commit-ID: 5871968d531f39c23a8e6c69525bb705bca52e04
Gitweb: http://git.kernel.org/tip/5871968d531f39c23a8e6c69525bb705bca52e04
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Tue, 24 Feb 2015 11:05:36 -0800
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Thu, 26 Feb 2015 16:04:37 -0800
rcu: Tighten up affinity and check for sysidle
If the RCU grace-period kthread invoking rcu_sysidle_check_cpu()
happens to be running on the tick_do_timer_cpu initially,
then rcu_bind_gp_kthread() won't bind it. This kthread might
then migrate before invoking rcu_gp_fqs(), which will trigger the
WARN_ON_ONCE() in rcu_sysidle_check_cpu(). This commit therefore makes
rcu_bind_gp_kthread() do the binding even if the kthread is currently
on the same CPU. Because this incurs added overhead, this commit also
causes each RCU grace-period kthread to invoke rcu_bind_gp_kthread()
once at boot rather than at the beginning of each grace period.
And as long as rcu_bind_gp_kthread() is being modified, this commit
eliminates its #ifdef.
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
kernel/rcu/tree.c | 2 +-
kernel/rcu/tree_plugin.h | 12 ++++++------
2 files changed, 7 insertions(+), 7 deletions(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 735bd7e..a6972c2 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1707,7 +1707,6 @@ static int rcu_gp_init(struct rcu_state *rsp)
struct rcu_node *rnp = rcu_get_root(rsp);
ACCESS_ONCE(rsp->gp_activity) = jiffies;
- rcu_bind_gp_kthread();
raw_spin_lock_irq(&rnp->lock);
smp_mb__after_unlock_lock();
if (!ACCESS_ONCE(rsp->gp_flags)) {
@@ -1895,6 +1894,7 @@ static int __noreturn rcu_gp_kthread(void *arg)
struct rcu_state *rsp = arg;
struct rcu_node *rnp = rcu_get_root(rsp);
+ rcu_bind_gp_kthread();
for (;;) {
/* Handle grace-period start. */
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 0a571e9..b46c928 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -2763,7 +2763,8 @@ static void rcu_sysidle_exit(int irq)
/*
* Check to see if the current CPU is idle. Note that usermode execution
- * does not count as idle. The caller must have disabled interrupts.
+ * does not count as idle. The caller must have disabled interrupts,
+ * and must be running on tick_do_timer_cpu.
*/
static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle,
unsigned long *maxj)
@@ -2784,8 +2785,8 @@ static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle,
if (!*isidle || rdp->rsp != rcu_state_p ||
cpu_is_offline(rdp->cpu) || rdp->cpu == tick_do_timer_cpu)
return;
- if (rcu_gp_in_progress(rdp->rsp))
- WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu);
+ /* Verify affinity of current kthread. */
+ WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu);
/* Pick up current idle and NMI-nesting counter and check. */
cur = atomic_read(&rdtp->dynticks_idle);
@@ -3068,11 +3069,10 @@ static void rcu_bind_gp_kthread(void)
return;
#ifdef CONFIG_NO_HZ_FULL_SYSIDLE
cpu = tick_do_timer_cpu;
- if (cpu >= 0 && cpu < nr_cpu_ids && raw_smp_processor_id() != cpu)
+ if (cpu >= 0 && cpu < nr_cpu_ids)
set_cpus_allowed_ptr(current, cpumask_of(cpu));
#else /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */
- if (!is_housekeeping_cpu(raw_smp_processor_id()))
- housekeeping_affine(current);
+ housekeeping_affine(current);
#endif /* #else #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */
}
--
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