linux-kernel - [tip: sched/core] tracing, hardirq: No moar

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Message-ID: <167361306803.4906.14578212248675615041.tip-bot2@tip-bot2>
Date:   Fri, 13 Jan 2023 12:31:08 -0000
From:   "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     kernel test robot <lkp@...el.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: sched/core] tracing, hardirq: No moar _rcuidle() tracing

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     9aedeaed6fc6fe8452b9b8225e95cc2b8631ff91
Gitweb:        https://git.kernel.org/tip/9aedeaed6fc6fe8452b9b8225e95cc2b8631ff91
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Thu, 12 Jan 2023 20:43:49 +01:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Fri, 13 Jan 2023 11:48:16 +01:00

tracing, hardirq: No moar _rcuidle() tracing

Robot reported that trace_hardirqs_{on,off}() tickle the forbidden
_rcuidle() tracepoint through local_irq_{en,dis}able().

For 'sane' configs, these calls will only happen with RCU enabled and
as such can use the regular tracepoint. This also means it's possible
to trace them from NMI context again.

Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Link: https://lore.kernel.org/r/20230112195541.477416709@infradead.org
---
 kernel/trace/trace_preemptirq.c | 26 ++++++++++++++++++--------
 1 file changed, 18 insertions(+), 8 deletions(-)

diff --git a/kernel/trace/trace_preemptirq.c b/kernel/trace/trace_preemptirq.c
index 629f285..f992444 100644
--- a/kernel/trace/trace_preemptirq.c
+++ b/kernel/trace/trace_preemptirq.c
@@ -20,6 +20,20 @@
 static DEFINE_PER_CPU(int, tracing_irq_cpu);
 
 /*
+ * Use regular trace points on architectures that implement noinstr
+ * tooling: these calls will only happen with RCU enabled, which can
+ * use a regular tracepoint.
+ *
+ * On older architectures, use the rcuidle tracing methods (which
+ * aren't NMI-safe - so exclude NMI contexts):
+ */
+#ifdef CONFIG_ARCH_WANTS_NO_INSTR
+#define trace(point)	trace_##point
+#else
+#define trace(point)	if (!in_nmi()) trace_##point##_rcuidle
+#endif
+
+/*
  * Like trace_hardirqs_on() but without the lockdep invocation. This is
  * used in the low level entry code where the ordering vs. RCU is important
  * and lockdep uses a staged approach which splits the lockdep hardirq
@@ -28,8 +42,7 @@ static DEFINE_PER_CPU(int, tracing_irq_cpu);
 void trace_hardirqs_on_prepare(void)
 {
 	if (this_cpu_read(tracing_irq_cpu)) {
-		if (!in_nmi())
-			trace_irq_enable(CALLER_ADDR0, CALLER_ADDR1);
+		trace(irq_enable)(CALLER_ADDR0, CALLER_ADDR1);
 		tracer_hardirqs_on(CALLER_ADDR0, CALLER_ADDR1);
 		this_cpu_write(tracing_irq_cpu, 0);
 	}
@@ -40,8 +53,7 @@ NOKPROBE_SYMBOL(trace_hardirqs_on_prepare);
 void trace_hardirqs_on(void)
 {
 	if (this_cpu_read(tracing_irq_cpu)) {
-		if (!in_nmi())
-			trace_irq_enable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);
+		trace(irq_enable)(CALLER_ADDR0, CALLER_ADDR1);
 		tracer_hardirqs_on(CALLER_ADDR0, CALLER_ADDR1);
 		this_cpu_write(tracing_irq_cpu, 0);
 	}
@@ -63,8 +75,7 @@ void trace_hardirqs_off_finish(void)
 	if (!this_cpu_read(tracing_irq_cpu)) {
 		this_cpu_write(tracing_irq_cpu, 1);
 		tracer_hardirqs_off(CALLER_ADDR0, CALLER_ADDR1);
-		if (!in_nmi())
-			trace_irq_disable(CALLER_ADDR0, CALLER_ADDR1);
+		trace(irq_disable)(CALLER_ADDR0, CALLER_ADDR1);
 	}
 
 }
@@ -78,8 +89,7 @@ void trace_hardirqs_off(void)
 	if (!this_cpu_read(tracing_irq_cpu)) {
 		this_cpu_write(tracing_irq_cpu, 1);
 		tracer_hardirqs_off(CALLER_ADDR0, CALLER_ADDR1);
-		if (!in_nmi())
-			trace_irq_disable_rcuidle(CALLER_ADDR0, CALLER_ADDR1);
+		trace(irq_disable)(CALLER_ADDR0, CALLER_ADDR1);
 	}
 }
 EXPORT_SYMBOL(trace_hardirqs_off);