rcu/context-tracking: Remove rcu_irq_enter/exit()

Now rcu_irq_enter/exit() is an unnecessary middle call between
ct_irq_enter/exit() and nmi_irq_enter/exit(). Take this opportunity
to remove the former functions and move the comments above them to the
new entrypoints.

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>

1 files changed, 67 insertions, 4 deletions

diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index b8a731f20778..c0d86dac98f1 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -36,24 +36,87 @@ void ct_idle_exit(void)
 }
 EXPORT_SYMBOL_GPL(ct_idle_exit);
 
+/**
+ * ct_irq_enter - inform RCU that current CPU is entering irq away from idle
+ *
+ * Enter an interrupt handler, which might possibly result in exiting
+ * idle mode, in other words, entering the mode in which read-side critical
+ * sections can occur.  The caller must have disabled interrupts.
+ *
+ * Note that the Linux kernel is fully capable of entering an interrupt
+ * handler that it never exits, for example when doing upcalls to user mode!
+ * This code assumes that the idle loop never does upcalls to user mode.
+ * If your architecture's idle loop does do upcalls to user mode (or does
+ * anything else that results in unbalanced calls to the irq_enter() and
+ * irq_exit() functions), RCU will give you what you deserve, good and hard.
+ * But very infrequently and irreproducibly.
+ *
+ * Use things like work queues to work around this limitation.
+ *
+ * You have been warned.
+ *
+ * If you add or remove a call to ct_irq_enter(), be sure to test with
+ * CONFIG_RCU_EQS_DEBUG=y.
+ */
 noinstr void ct_irq_enter(void)
 {
-	rcu_irq_enter();
+	lockdep_assert_irqs_disabled();
+	ct_nmi_enter();
 }
 
+/**
+ * ct_irq_exit - inform RCU that current CPU is exiting irq towards idle
+ *
+ * Exit from an interrupt handler, which might possibly result in entering
+ * idle mode, in other words, leaving the mode in which read-side critical
+ * sections can occur.  The caller must have disabled interrupts.
+ *
+ * This code assumes that the idle loop never does anything that might
+ * result in unbalanced calls to irq_enter() and irq_exit().  If your
+ * architecture's idle loop violates this assumption, RCU will give you what
+ * you deserve, good and hard.  But very infrequently and irreproducibly.
+ *
+ * Use things like work queues to work around this limitation.
+ *
+ * You have been warned.
+ *
+ * If you add or remove a call to ct_irq_exit(), be sure to test with
+ * CONFIG_RCU_EQS_DEBUG=y.
+ */
 noinstr void ct_irq_exit(void)
 {
-	rcu_irq_exit();
+	lockdep_assert_irqs_disabled();
+	ct_nmi_exit();
 }
 
+/*
+ * Wrapper for ct_irq_enter() where interrupts are enabled.
+ *
+ * If you add or remove a call to ct_irq_enter_irqson(), be sure to test
+ * with CONFIG_RCU_EQS_DEBUG=y.
+ */
 void ct_irq_enter_irqson(void)
 {
-	rcu_irq_enter_irqson();
+	unsigned long flags;
+
+	local_irq_save(flags);
+	ct_irq_enter();
+	local_irq_restore(flags);
 }
 
+/*
+ * Wrapper for ct_irq_exit() where interrupts are enabled.
+ *
+ * If you add or remove a call to ct_irq_exit_irqson(), be sure to test
+ * with CONFIG_RCU_EQS_DEBUG=y.
+ */
 void ct_irq_exit_irqson(void)
 {
-	rcu_irq_exit_irqson();
+	unsigned long flags;
+
+	local_irq_save(flags);
+	ct_irq_exit();
+	local_irq_restore(flags);
 }
 
 noinstr void ct_nmi_enter(void)