By default we don't want to enter into RCU extended quiescent
state while in userspace because doing this produces some overhead
(eg: use of syscall slowpath). Set it off by default and ready to
run when some feature like adaptive tickless need it.
Signed-off-by: Frederic Weisbecker <fweis...@gmail.com>
Cc: Alessio Igor Bogani <abog...@kernel.org>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Avi Kivity <a...@redhat.com>
Cc: Chris Metcalf <cmetc...@tilera.com>
Cc: Christoph Lameter <c...@linux.com>
Cc: Geoff Levand <ge...@infradead.org>
Cc: Gilad Ben Yossef <gi...@benyossef.com>
Cc: Hakan Akkan <hakanak...@gmail.com>
Cc: H. Peter Anvin <h...@zytor.com>
Cc: Ingo Molnar <mi...@kernel.org>
Cc: Josh Triplett <j...@joshtriplett.org>
Cc: Kevin Hilman <khil...@ti.com>
Cc: Max Krasnyansky <m...@qualcomm.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Stephen Hemminger <shemmin...@vyatta.com>
Cc: Steven Rostedt <rost...@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporat...@gmail.com>
Cc: Thomas Gleixner <t...@linutronix.de>
---
kernel/rcutree.c | 5 ++++-
kernel/rcutree.h | 1 +
2 files changed, 5 insertions(+), 1 deletions(-)
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index d5df618..78b0c30 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -209,6 +209,9 @@ EXPORT_SYMBOL_GPL(rcu_note_context_switch);
DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
.dynticks_nesting = DYNTICK_TASK_EXIT_IDLE,
.dynticks = ATOMIC_INIT(1),
+#ifdef CONFIG_RCU_USER_QS
+ .ignore_user_qs = true,
+#endif
};
static int blimit = 10; /* Maximum callbacks per rcu_do_batch.
*/
@@ -442,7 +445,7 @@ void rcu_user_enter(void)
local_irq_save(flags);
rdtp = &__get_cpu_var(rcu_dynticks);
- if (!rdtp->in_user) {
+ if (!rdtp->ignore_user_qs && !rdtp->in_user) {
rdtp->in_user = true;
rcu_eqs_enter(1);
}
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 4d82cb5..55bcef1 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -103,6 +103,7 @@ struct rcu_dynticks {
int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */
#endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
#ifdef CONFIG_RCU_USER_QS
+ bool ignore_user_qs; /* Treat userspace as extended QS or not */
bool in_user; /* Is the CPU in userland from RCU POV? */
#endif
};
--
1.7.5.4
--
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