Commit-ID: 1e1a689f10a27a4fe1ab9b4c6db04fa7232746a5
Gitweb: http://git.kernel.org/tip/1e1a689f10a27a4fe1ab9b4c6db04fa7232746a5
Author: Frederic Weisbecker <fweisbec@xxxxxxxxx>
AuthorDate: Wed, 11 Jul 2012 20:26:32 +0200
Committer: Frederic Weisbecker <fweisbec@xxxxxxxxx>
CommitDate: Wed, 26 Sep 2012 15:47:01 +0200
rcu: Ignore userspace extended quiescent state by default
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 <fweisbec@xxxxxxxxx>
Cc: Alessio Igor Bogani <abogani@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Avi Kivity <avi@xxxxxxxxxx>
Cc: Chris Metcalf <cmetcalf@xxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Geoff Levand <geoff@xxxxxxxxxxxxx>
Cc: Gilad Ben Yossef <gilad@xxxxxxxxxxxxx>
Cc: Hakan Akkan <hakanakkan@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
Cc: Kevin Hilman <khilman@xxxxxx>
Cc: Max Krasnyansky <maxk@xxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Stephen Hemminger <shemminger@xxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Sven-Thorsten Dietrich <thebigcorporation@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
---
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 d62c044..6b82a95 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -206,6 +206,9 @@ 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. */
@@ -430,7 +433,7 @@ 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 10cc2f9..5faf05d 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
};
--
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