linux-kernel - Re: [PATCH v2 11/11] lockdep,trace: Expose tracepoints

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Date:   Thu, 3 Sep 2020 17:36:49 +0200
From:   peterz@...radead.org
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     linux-kernel@...r.kernel.org, mingo@...nel.org, will@...nel.org,
        npiggin@...il.com, elver@...gle.com, jgross@...e.com,
        paulmck@...nel.org, rostedt@...dmis.org, rjw@...ysocki.net,
        joel@...lfernandes.org, svens@...ux.ibm.com, tglx@...utronix.de,
        ulf.hansson@...aro.org, viresh.kumar@...aro.org,
        vincent.guittot@...aro.org
Subject: Re: [PATCH v2 11/11] lockdep,trace: Expose tracepoints

On Thu, Sep 03, 2020 at 08:19:38AM -0700, Guenter Roeck wrote:
> This doesn't compile for me - there is no "name" parameter in __DO_TRACE().
> 
> Error log:
> In file included from ./include/linux/rculist.h:11,
>                  from ./include/linux/pid.h:5,
>                  from ./include/linux/sched.h:14,
>                  from ./include/linux/sched/numa_balancing.h:10,
>                  from ./include/trace/events/sched.h:8,
>                  from kernel/sched/core.c:10:
> ./include/trace/events/sched.h: In function 'trace_sched_kthread_stop':
> ./include/linux/tracepoint.h:175:26: error: '__tracepoint_name' undeclared
> 
> I applied your patch on top of v5.9-rc3-75-gfc3abb53250a. Are you using
> a different branch ?

Argh, I was on tip/master... easy fix though.

---
diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index 7d9c1c0e149c..878bac893e41 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -27,17 +27,20 @@
  *         SOFTIRQ_MASK:	0x0000ff00
  *         HARDIRQ_MASK:	0x000f0000
  *             NMI_MASK:	0x00f00000
+ *         RCUIDLE_MASK:	0x01000000
  * PREEMPT_NEED_RESCHED:	0x80000000
  */
 #define PREEMPT_BITS	8
 #define SOFTIRQ_BITS	8
 #define HARDIRQ_BITS	4
 #define NMI_BITS	4
+#define RCUIDLE_BITS	1
 
 #define PREEMPT_SHIFT	0
 #define SOFTIRQ_SHIFT	(PREEMPT_SHIFT + PREEMPT_BITS)
 #define HARDIRQ_SHIFT	(SOFTIRQ_SHIFT + SOFTIRQ_BITS)
 #define NMI_SHIFT	(HARDIRQ_SHIFT + HARDIRQ_BITS)
+#define RCUIDLE_SHIFT	(NMI_SHIFT     + NMI_BITS)
 
 #define __IRQ_MASK(x)	((1UL << (x))-1)
 
@@ -45,11 +48,13 @@
 #define SOFTIRQ_MASK	(__IRQ_MASK(SOFTIRQ_BITS) << SOFTIRQ_SHIFT)
 #define HARDIRQ_MASK	(__IRQ_MASK(HARDIRQ_BITS) << HARDIRQ_SHIFT)
 #define NMI_MASK	(__IRQ_MASK(NMI_BITS)     << NMI_SHIFT)
+#define RCUIDLE_MASK	(__IRQ_MASK(RCUIDLE_BITS) << RCUIDLE_SHIFT)
 
 #define PREEMPT_OFFSET	(1UL << PREEMPT_SHIFT)
 #define SOFTIRQ_OFFSET	(1UL << SOFTIRQ_SHIFT)
 #define HARDIRQ_OFFSET	(1UL << HARDIRQ_SHIFT)
 #define NMI_OFFSET	(1UL << NMI_SHIFT)
+#define RCUIDLE_OFFSET	(1UL << RCUIDLE_SHIFT)
 
 #define SOFTIRQ_DISABLE_OFFSET	(2 * SOFTIRQ_OFFSET)
 
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 598fec9f9dbf..0469bc1c24fc 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -164,12 +164,18 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
 		void *__data;						\
 		int __maybe_unused __idx = 0;				\
 									\
-		if (!(cond))						\
+		if (!(cond) || (preempt_count() & RCUIDLE_MASK))	\
 			return;						\
 									\
 		/* srcu can't be used from NMI */			\
 		WARN_ON_ONCE(rcuidle && in_nmi());			\
 									\
+		if (IS_ENABLED(CONFIG_LOCKDEP) && !(rcuidle)) {		\
+			rcu_read_lock_sched_notrace();			\
+			rcu_dereference_sched((tp)->funcs);		\
+			rcu_read_unlock_sched_notrace();		\
+		}							\
+									\
 		/* keep srcu and sched-rcu usage consistent */		\
 		preempt_disable_notrace();				\
 									\
@@ -235,11 +241,6 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
 				TP_PROTO(data_proto),			\
 				TP_ARGS(data_args),			\
 				TP_CONDITION(cond), 0);			\
-		if (IS_ENABLED(CONFIG_LOCKDEP) && (cond)) {		\
-			rcu_read_lock_sched_notrace();			\
-			rcu_dereference_sched(__tracepoint_##name.funcs);\
-			rcu_read_unlock_sched_notrace();		\
-		}							\
 	}								\
 	__DECLARE_TRACE_RCU(name, PARAMS(proto), PARAMS(args),		\
 		PARAMS(cond), PARAMS(data_proto), PARAMS(data_args))	\
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 8ce77d9ac716..ad9fb4f12c63 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -269,6 +269,8 @@ static noinstr void rcu_dynticks_eqs_enter(void)
 	/* Better not have special action (TLB flush) pending! */
 	WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
 		     (seq & RCU_DYNTICK_CTRL_MASK));
+
+	__preempt_count_add(RCUIDLE_OFFSET);
 }
 
 /*
@@ -281,6 +283,8 @@ static noinstr void rcu_dynticks_eqs_exit(void)
 	struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
 	int seq;
 
+	__preempt_count_sub(RCUIDLE_OFFSET);
+
 	/*
 	 * CPUs seeing atomic_add_return() must see prior idle sojourns,
 	 * and we also must force ordering with the next RCU read-side