context_tracking: Take NMI eqs entrypoints over RCU

The RCU dynticks counter is going to be merged into the context tracking
subsystem. Prepare with moving the NMI extended quiescent states
entrypoints to context tracking. For now those are dumb redirection to
existing RCU calls.

Acked-by: Paul E. McKenney <[email protected]>
Signed-off-by: Frederic Weisbecker <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Neeraj Upadhyay <[email protected]>
Cc: Uladzislau Rezki <[email protected]>
Cc: Joel Fernandes <[email protected]>
Cc: Boqun Feng <[email protected]>
Cc: Nicolas Saenz Julienne <[email protected]>
Cc: Marcelo Tosatti <[email protected]>
Cc: Xiongfeng Wang <[email protected]>
Cc: Yu Liao <[email protected]>
Cc: Phil Auld <[email protected]>
Cc: Paul Gortmaker<[email protected]>
Cc: Alex Belits <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Reviewed-by: Nicolas Saenz Julienne <[email protected]>
Tested-by: Nicolas Saenz Julienne <[email protected]>

Author: Frederic Weisbecker

Documentation/RCU/Design/Requirements/Requirements.rst

@@ -1847,7 +1847,7 @@ normal interrupts. One way that this can happen is for code that
 directly invokes ct_irq_enter() and ct_irq_exit() to be called
 from an NMI handler. This astonishing fact of life prompted the current
 code structure, which has ct_irq_enter() invoking
-rcu_nmi_enter() and ct_irq_exit() invoking rcu_nmi_exit().
+ct_nmi_enter() and ct_irq_exit() invoking ct_nmi_exit().
 And yes, I also learned of this requirement the hard way.
 
 Loadable Modules

arch/Kconfig

@@ -797,7 +797,7 @@ config HAVE_CONTEXT_TRACKING_USER_OFFSTACK
 
 	  - Critical entry code isn't preemptible (or better yet:
 	    not interruptible).
-	  - No use of RCU read side critical sections, unless rcu_nmi_enter()
+	  - No use of RCU read side critical sections, unless ct_nmi_enter()
 	    got called.
 	  - No use of instrumentation, unless instrumentation_begin() got
 	    called.

arch/arm64/kernel/entry-common.c

@@ -161,7 +161,7 @@ static void noinstr arm64_enter_nmi(struct pt_regs *regs)
 	__nmi_enter();
 	lockdep_hardirqs_off(CALLER_ADDR0);
 	lockdep_hardirq_enter();
-	rcu_nmi_enter();
+	ct_nmi_enter();
 
 	trace_hardirqs_off_finish();
 	ftrace_nmi_enter();
@@ -182,7 +182,7 @@ static void noinstr arm64_exit_nmi(struct pt_regs *regs)
 		lockdep_hardirqs_on_prepare();
 	}
 
-	rcu_nmi_exit();
+	ct_nmi_exit();
 	lockdep_hardirq_exit();
 	if (restore)
 		lockdep_hardirqs_on(CALLER_ADDR0);
@@ -199,7 +199,7 @@ static void noinstr arm64_enter_el1_dbg(struct pt_regs *regs)
 	regs->lockdep_hardirqs = lockdep_hardirqs_enabled();
 
 	lockdep_hardirqs_off(CALLER_ADDR0);
-	rcu_nmi_enter();
+	ct_nmi_enter();
 
 	trace_hardirqs_off_finish();
 }
@@ -218,7 +218,7 @@ static void noinstr arm64_exit_el1_dbg(struct pt_regs *regs)
 		lockdep_hardirqs_on_prepare();
 	}
 
-	rcu_nmi_exit();
+	ct_nmi_exit();
 	if (restore)
 		lockdep_hardirqs_on(CALLER_ADDR0);
 }

include/linux/context_tracking_irq.h

@@ -7,11 +7,15 @@ void ct_irq_enter(void);
 void ct_irq_exit(void);
 void ct_irq_enter_irqson(void);
 void ct_irq_exit_irqson(void);
+void ct_nmi_enter(void);
+void ct_nmi_exit(void);
 #else
 static inline void ct_irq_enter(void) { }
 static inline void ct_irq_exit(void) { }
 static inline void ct_irq_enter_irqson(void) { }
 static inline void ct_irq_exit_irqson(void) { }
+static inline void ct_nmi_enter(void) { }
+static inline void ct_nmi_exit(void) { }
 #endif
 
 #endif

include/linux/hardirq.h

@@ -124,7 +124,7 @@ extern void rcu_nmi_exit(void);
 	do {							\
 		__nmi_enter();					\
 		lockdep_hardirq_enter();			\
-		rcu_nmi_enter();				\
+		ct_nmi_enter();				\
 		instrumentation_begin();			\
 		ftrace_nmi_enter();				\
 		instrumentation_end();				\
@@ -143,7 +143,7 @@ extern void rcu_nmi_exit(void);
 		instrumentation_begin();			\
 		ftrace_nmi_exit();				\
 		instrumentation_end();				\
-		rcu_nmi_exit();					\
+		ct_nmi_exit();					\
 		lockdep_hardirq_exit();				\
 		__nmi_exit();					\
 	} while (0)

kernel/context_tracking.c

@@ -55,6 +55,16 @@ void ct_irq_exit_irqson(void)
 {
 	rcu_irq_exit_irqson();
 }
+
+noinstr void ct_nmi_enter(void)
+{
+	rcu_nmi_enter();
+}
+
+noinstr void ct_nmi_exit(void)
+{
+	rcu_nmi_exit();
+}
 #endif /* #ifdef CONFIG_CONTEXT_TRACKING_IDLE */
 
 #ifdef CONFIG_CONTEXT_TRACKING_USER

kernel/entry/common.c

@@ -449,7 +449,7 @@ irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs)
 	__nmi_enter();
 	lockdep_hardirqs_off(CALLER_ADDR0);
 	lockdep_hardirq_enter();
-	rcu_nmi_enter();
+	ct_nmi_enter();
 
 	instrumentation_begin();
 	trace_hardirqs_off_finish();
@@ -469,7 +469,7 @@ void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state)
 	}
 	instrumentation_end();
 
-	rcu_nmi_exit();
+	ct_nmi_exit();
 	lockdep_hardirq_exit();
 	if (irq_state.lockdep)
 		lockdep_hardirqs_on(CALLER_ADDR0);

kernel/extable.c

@@ -114,7 +114,7 @@ int kernel_text_address(unsigned long addr)
 
 	/* Treat this like an NMI as it can happen anywhere */
 	if (no_rcu)
-		rcu_nmi_enter();
+		ct_nmi_enter();
 
 	if (is_module_text_address(addr))
 		goto out;
@@ -127,7 +127,7 @@ int kernel_text_address(unsigned long addr)
 	ret = 0;
 out:
 	if (no_rcu)
-		rcu_nmi_exit();
+		ct_nmi_exit();
 
 	return ret;
 }

kernel/trace/trace.c

@@ -3105,7 +3105,7 @@ void __trace_stack(struct trace_array *tr, unsigned int trace_ctx,
 	}
 
 	/*
-	 * When an NMI triggers, RCU is enabled via rcu_nmi_enter(),
+	 * When an NMI triggers, RCU is enabled via ct_nmi_enter(),
 	 * but if the above rcu_is_watching() failed, then the NMI
 	 * triggered someplace critical, and ct_irq_enter() should
 	 * not be called from NMI.