rcu/context-tracking: Move deferred nocb resched to context tracking

To prepare for migrating the RCU eqs accounting code to context tracking,
split the last-resort deferred nocb resched from rcu_user_enter() and
move it into a separate call from context tracking.

Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Uladzislau Rezki <uladzislau.rezki@sony.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Nicolas Saenz Julienne <nsaenz@kernel.org>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Cc: Yu Liao <liaoyu15@huawei.com>
Cc: Phil Auld <pauld@redhat.com>
Cc: Paul Gortmaker<paul.gortmaker@windriver.com>
Cc: Alex Belits <abelits@marvell.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Tested-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index f1562d9..3717cad 100644 (file)
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -112,6 +112,12 @@ static inline void rcu_user_enter(void) { }
 static inline void rcu_user_exit(void) { }
 #endif /* CONFIG_NO_HZ_FULL */
 
+#if defined(CONFIG_NO_HZ_FULL) && (!defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_KVM_XFER_TO_GUEST_WORK))
+void rcu_irq_work_resched(void);
+#else
+static inline void rcu_irq_work_resched(void) { }
+#endif
+
 #ifdef CONFIG_RCU_NOCB_CPU
 void rcu_init_nohz(void);
 int rcu_nocb_cpu_offload(int cpu);

diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 7c3033e..8cf59d8 100644 (file)
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -177,6 +177,8 @@ static __always_inline void context_tracking_recursion_exit(void)
  */
 void noinstr __ct_user_enter(enum ctx_state state)
 {
+       lockdep_assert_irqs_disabled();
+
        /* Kernel threads aren't supposed to go to userspace */
        WARN_ON_ONCE(!current->mm);
 
@@ -198,6 +200,12 @@ void noinstr __ct_user_enter(enum ctx_state state)
                                vtime_user_enter(current);
                                instrumentation_end();
                        }
+                       /*
+                        * Other than generic entry implementation, we may be past the last
+                        * rescheduling opportunity in the entry code. Trigger a self IPI
+                        * that will fire and reschedule once we resume in user/guest mode.
+                        */
+                       rcu_irq_work_resched();
                        rcu_user_enter();
                }
                /*

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 006939b..8c0c349 100644 (file)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -681,7 +681,7 @@ static DEFINE_PER_CPU(struct irq_work, late_wakeup_work) =
  * last resort is to fire a local irq_work that will trigger a reschedule once IRQs
  * get re-enabled again.
  */
-noinstr static void rcu_irq_work_resched(void)
+noinstr void rcu_irq_work_resched(void)
 {
        struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
 
@@ -697,10 +697,7 @@ noinstr static void rcu_irq_work_resched(void)
        }
        instrumentation_end();
 }
-
-#else
-static inline void rcu_irq_work_resched(void) { }
-#endif
+#endif /* #if !defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_KVM_XFER_TO_GUEST_WORK) */
 
 /**
  * rcu_user_enter - inform RCU that we are resuming userspace.
@@ -715,14 +712,6 @@ static inline void rcu_irq_work_resched(void) { }
  */
 noinstr void rcu_user_enter(void)
 {
-       lockdep_assert_irqs_disabled();
-
-       /*
-        * Other than generic entry implementation, we may be past the last
-        * rescheduling opportunity in the entry code. Trigger a self IPI
-        * that will fire and reschedule once we resume in user/guest mode.
-        */
-       rcu_irq_work_resched();
        rcu_eqs_enter(true);
 }