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authorFrederic Weisbecker <fweisbec@gmail.com>2012-07-11 20:26:32 +0200
committerFrederic Weisbecker <fweisbec@gmail.com>2012-09-26 15:47:01 +0200
commit1e1a689f10a27a4fe1ab9b4c6db04fa7232746a5 (patch)
tree098f180287723813d248f59f452ca3a7db04b636 /kernel
parentc5d900bf676b1e2a61c44483932c8088651bbb4e (diff)
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@gmail.com> Cc: Alessio Igor Bogani <abogani@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Avi Kivity <avi@redhat.com> 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: H. Peter Anvin <hpa@zytor.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Kevin Hilman <khilman@ti.com> Cc: Max Krasnyansky <maxk@qualcomm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephen Hemminger <shemminger@vyatta.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/rcutree.c5
-rw-r--r--kernel/rcutree.h1
2 files changed, 5 insertions, 1 deletions
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index d62c04482228..6b82a9565149 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 10cc2f9f8433..5faf05d68326 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
};