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Message-ID: <20241205093724.16c2a14d@gandalf.local.home>
Date: Thu, 5 Dec 2024 09:37:24 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Masami Hiramatsu
<mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Mark Rutland <mark.rutland@....com>, Kuan-Wei Chiu <visitorckw@...il.com>,
Peter Zijlstra <peterz@...radead.org>, Geert Uytterhoeven
<geert@...ux-m68k.org>, "Paul E. McKenney" <paulmck@...nel.org>, Guenter
Roeck <linux@...ck-us.net>, Madhavan Srinivasan <maddy@...ux.ibm.com>
Subject: [GIT PULL] tracing: Fixes for v6.13-rc1
Linus,
tracing fixes for v6.13:
- Fix trace histogram sort function cmp_entries_dup()
The sort function cmp_entries_dup() returns either 1 or 0, and not
-1 if parameter "a" is less than "b" by memcmp().
- Fix archs that call trace_hardirqs_off() without RCU watching
Both x86 and arm64 no longer call any tracepoints with RCU not
watching. It was assumed that it was safe to get rid of
trace_*_rcuidle() version of the tracepoint calls. This was needed
to get rid of the SRCU protection and be able to implement features
like faultable traceponits and add rust tracepoints.
Unfortunately, there were a few architectures that still relied on
that logic. There's only one file that has tracepoints that are
called without RCU watching. Add macro logic around the tracepoints
for architectures that do not have CONFIG_ARCH_WANTS_NO_INSTR defined
will check if the code is in the idle path (the only place RCU isn't
watching), and enable RCU around calling the tracepoint, but only
do it if the tracepoint is enabled.
Please pull the latest trace-v6.13-rc1 tree, which can be found at:
git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace.git
trace-v6.13-rc1
Tag SHA1: 37bbbac90061b19b3ea6410a57a20742fd648ea6
Head SHA1: dc1b157b828dfe412c776ac1dd8db158f6016b39
Kuan-Wei Chiu (1):
tracing: Fix cmp_entries_dup() to respect sort() comparison rules
Steven Rostedt (1):
tracing: Fix archs that still call tracepoints without RCU watching
----
kernel/trace/trace_preemptirq.c | 43 +++++++++++++++++++++++++++++++++++------
kernel/trace/tracing_map.c | 6 +-----
2 files changed, 38 insertions(+), 11 deletions(-)
---------------------------
diff --git a/kernel/trace/trace_preemptirq.c b/kernel/trace/trace_preemptirq.c
index 5c03633316a6..0c42b15c3800 100644
--- a/kernel/trace/trace_preemptirq.c
+++ b/kernel/trace/trace_preemptirq.c
@@ -10,11 +10,42 @@
#include <linux/module.h>
#include <linux/ftrace.h>
#include <linux/kprobes.h>
+#include <linux/hardirq.h>
#include "trace.h"
#define CREATE_TRACE_POINTS
#include <trace/events/preemptirq.h>
+/*
+ * 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, RCU may not be watching in idle. In that
+ * case, wake up RCU to watch while calling the tracepoint. These
+ * aren't NMI-safe - so exclude NMI contexts:
+ */
+#ifdef CONFIG_ARCH_WANTS_NO_INSTR
+#define trace(point, args) trace_##point(args)
+#else
+#define trace(point, args) \
+ do { \
+ if (trace_##point##_enabled()) { \
+ bool exit_rcu = false; \
+ if (in_nmi()) \
+ break; \
+ if (!IS_ENABLED(CONFIG_TINY_RCU) && \
+ is_idle_task(current)) { \
+ ct_irq_enter(); \
+ exit_rcu = true; \
+ } \
+ trace_##point(args); \
+ if (exit_rcu) \
+ ct_irq_exit(); \
+ } \
+ } while (0)
+#endif
+
#ifdef CONFIG_TRACE_IRQFLAGS
/* Per-cpu variable to prevent redundant calls when IRQs already off */
static DEFINE_PER_CPU(int, tracing_irq_cpu);
@@ -28,7 +59,7 @@ static DEFINE_PER_CPU(int, tracing_irq_cpu);
void trace_hardirqs_on_prepare(void)
{
if (this_cpu_read(tracing_irq_cpu)) {
- trace_irq_enable(CALLER_ADDR0, CALLER_ADDR1);
+ trace(irq_enable, TP_ARGS(CALLER_ADDR0, CALLER_ADDR1));
tracer_hardirqs_on(CALLER_ADDR0, CALLER_ADDR1);
this_cpu_write(tracing_irq_cpu, 0);
}
@@ -39,7 +70,7 @@ NOKPROBE_SYMBOL(trace_hardirqs_on_prepare);
void trace_hardirqs_on(void)
{
if (this_cpu_read(tracing_irq_cpu)) {
- trace_irq_enable(CALLER_ADDR0, CALLER_ADDR1);
+ trace(irq_enable, TP_ARGS(CALLER_ADDR0, CALLER_ADDR1));
tracer_hardirqs_on(CALLER_ADDR0, CALLER_ADDR1);
this_cpu_write(tracing_irq_cpu, 0);
}
@@ -61,7 +92,7 @@ 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);
- trace_irq_disable(CALLER_ADDR0, CALLER_ADDR1);
+ trace(irq_disable, TP_ARGS(CALLER_ADDR0, CALLER_ADDR1));
}
}
@@ -75,7 +106,7 @@ 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);
- trace_irq_disable(CALLER_ADDR0, CALLER_ADDR1);
+ trace(irq_disable, TP_ARGS(CALLER_ADDR0, CALLER_ADDR1));
}
}
EXPORT_SYMBOL(trace_hardirqs_off);
@@ -86,13 +117,13 @@ NOKPROBE_SYMBOL(trace_hardirqs_off);
void trace_preempt_on(unsigned long a0, unsigned long a1)
{
- trace_preempt_enable(a0, a1);
+ trace(preempt_enable, TP_ARGS(a0, a1));
tracer_preempt_on(a0, a1);
}
void trace_preempt_off(unsigned long a0, unsigned long a1)
{
- trace_preempt_disable(a0, a1);
+ trace(preempt_disable, TP_ARGS(a0, a1));
tracer_preempt_off(a0, a1);
}
#endif
diff --git a/kernel/trace/tracing_map.c b/kernel/trace/tracing_map.c
index 3a56e7c8aa4f..1921ade45be3 100644
--- a/kernel/trace/tracing_map.c
+++ b/kernel/trace/tracing_map.c
@@ -845,15 +845,11 @@ int tracing_map_init(struct tracing_map *map)
static int cmp_entries_dup(const void *A, const void *B)
{
const struct tracing_map_sort_entry *a, *b;
- int ret = 0;
a = *(const struct tracing_map_sort_entry **)A;
b = *(const struct tracing_map_sort_entry **)B;
- if (memcmp(a->key, b->key, a->elt->map->key_size))
- ret = 1;
-
- return ret;
+ return memcmp(a->key, b->key, a->elt->map->key_size);
}
static int cmp_entries_sum(const void *A, const void *B)
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