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Message-ID: <20250507162049.30a3ccae@gandalf.local.home>
Date: Wed, 7 May 2025 16:20:49 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: LKML <linux-kernel@...r.kernel.org>, Linux Trace Kernel
<linux-trace-kernel@...r.kernel.org>, bpf@...r.kernel.org, netdev
<netdev@...r.kernel.org>
Cc: Jiri Olsa <olsajiri@...il.com>, Peter Zijlstra <peterz@...radead.org>,
David Ahern <dsahern@...nel.org>, Juri Lelli <juri.lelli@...il.com>, Breno
Leitao <leitao@...ian.org>, Alexei Starovoitov
<alexei.starovoitov@...il.com>, Andrii Nakryiko
<andrii.nakryiko@...il.com>, Gabriele Monaco <gmonaco@...hat.com>, Masami
Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers
<mathieu.desnoyers@...icios.com>
Subject: [PATCH v2] tracepoint: Have tracepoints created with
DECLARE_TRACE() have _tp suffix
From: Steven Rostedt <rostedt@...dmis.org>
Most tracepoints in the kernel are created with TRACE_EVENT(). The
TRACE_EVENT() macro (and DECLARE_EVENT_CLASS() and DEFINE_EVENT() where in
reality, TRACE_EVENT() is just a helper macro that calls those other two
macros), will create not only a tracepoint (the function trace_<event>()
used in the kernel), it also exposes the tracepoint to user space along
with defining what fields will be saved by that tracepoint.
There are a few places that tracepoints are created in the kernel that are
not exposed to userspace via tracefs. They can only be accessed from code
within the kernel. These tracepoints are created with DEFINE_TRACE()
Most of these tracepoints end with "_tp". This is useful as when the
developer sees that, they know that the tracepoint is for in-kernel only
(meaning it can only be accessed inside the kernel, either directly by the
kernel or indirectly via modules and BPF programs) and is not exposed to
user space.
Instead of making this only a process to add "_tp", enforce it by making
the DECLARE_TRACE() append the "_tp" suffix to the tracepoint. This
requires adding DECLARE_TRACE_EVENT() macros for the TRACE_EVENT() macro
to use that keeps the original name.
Link: https://lore.kernel.org/all/20250418083351.20a60e64@gandalf.local.home/
Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: David Ahern <dsahern@...nel.org>
Cc: Juri Lelli <juri.lelli@...il.com>
Cc: Breno Leitao <leitao@...ian.org>
Cc: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: Gabriele Monaco <gmonaco@...hat.com>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Acked-by: Andrii Nakryiko <andrii@...nel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
Changes since RFC/v1: https://lore.kernel.org/20250418110104.12af6883@gandalf.local.home
- Folded in Jiri Olsa's update to DECLARE_TRACE_WRITABLE()
https://lore.kernel.org/linux-trace-kernel/aAY9pcvYHkYKFwZ5@krava/
- Updated change log to be more specific about "kernel only"
(Andrii Nakryiko)
- Updated Documentation to ref
Documentation/trace/tracepoints.rst | 17 ++++++---
include/linux/tracepoint.h | 38 +++++++++++++------
include/trace/bpf_probe.h | 8 ++--
include/trace/define_trace.h | 17 ++++++++-
include/trace/events/sched.h | 30 +++++++--------
include/trace/events/tcp.h | 2 +-
.../bpf/test_kmods/bpf_testmod-events.h | 2 +-
.../selftests/bpf/test_kmods/bpf_testmod.c | 8 ++--
8 files changed, 78 insertions(+), 44 deletions(-)
diff --git a/Documentation/trace/tracepoints.rst b/Documentation/trace/tracepoints.rst
index decabcc77b56..b35c40e3abbe 100644
--- a/Documentation/trace/tracepoints.rst
+++ b/Documentation/trace/tracepoints.rst
@@ -71,7 +71,7 @@ In subsys/file.c (where the tracing statement must be added)::
void somefct(void)
{
...
- trace_subsys_eventname(arg, task);
+ trace_subsys_eventname_tp(arg, task);
...
}
@@ -129,12 +129,12 @@ within an if statement with the following::
for (i = 0; i < count; i++)
tot += calculate_nuggets();
- trace_foo_bar(tot);
+ trace_foo_bar_tp(tot);
}
-All trace_<tracepoint>() calls have a matching trace_<tracepoint>_enabled()
+All trace_<tracepoint>_tp() calls have a matching trace_<tracepoint>_enabled()
function defined that returns true if the tracepoint is enabled and
-false otherwise. The trace_<tracepoint>() should always be within the
+false otherwise. The trace_<tracepoint>_tp() should always be within the
block of the if (trace_<tracepoint>_enabled()) to prevent races between
the tracepoint being enabled and the check being seen.
@@ -143,7 +143,10 @@ the static_key of the tracepoint to allow the if statement to be implemented
with jump labels and avoid conditional branches.
.. note:: The convenience macro TRACE_EVENT provides an alternative way to
- define tracepoints. Check http://lwn.net/Articles/379903,
+ define tracepoints. Note, DECLARE_TRACE(foo) creates a function
+ "trace_foo_tp()" whereas TRACE_EVENT(foo) creates a function
+ "trace_foo()", and also exposes the tracepoint as a trace event in
+ /sys/kernel/tracing/events directory. Check http://lwn.net/Articles/379903,
http://lwn.net/Articles/381064 and http://lwn.net/Articles/383362
for a series of articles with more details.
@@ -159,7 +162,9 @@ In a C file::
void do_trace_foo_bar_wrapper(args)
{
- trace_foo_bar(args);
+ trace_foo_bar_tp(args); // for tracepoints created via DECLARE_TRACE
+ // or
+ trace_foo_bar(args); // for tracepoints created via TRACE_EVENT
}
In the header file::
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index a351763e6965..826ce3f8e1f8 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -464,16 +464,30 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
#endif
#define DECLARE_TRACE(name, proto, args) \
- __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), \
+ __DECLARE_TRACE(name##_tp, PARAMS(proto), PARAMS(args), \
cpu_online(raw_smp_processor_id()), \
PARAMS(void *__data, proto))
#define DECLARE_TRACE_CONDITION(name, proto, args, cond) \
- __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), \
+ __DECLARE_TRACE(name##_tp, PARAMS(proto), PARAMS(args), \
cpu_online(raw_smp_processor_id()) && (PARAMS(cond)), \
PARAMS(void *__data, proto))
#define DECLARE_TRACE_SYSCALL(name, proto, args) \
+ __DECLARE_TRACE_SYSCALL(name##_tp, PARAMS(proto), PARAMS(args), \
+ PARAMS(void *__data, proto))
+
+#define DECLARE_TRACE_EVENT(name, proto, args) \
+ __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), \
+ cpu_online(raw_smp_processor_id()), \
+ PARAMS(void *__data, proto))
+
+#define DECLARE_TRACE_EVENT_CONDITION(name, proto, args, cond) \
+ __DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), \
+ cpu_online(raw_smp_processor_id()) && (PARAMS(cond)), \
+ PARAMS(void *__data, proto))
+
+#define DECLARE_TRACE_EVENT_SYSCALL(name, proto, args) \
__DECLARE_TRACE_SYSCALL(name, PARAMS(proto), PARAMS(args), \
PARAMS(void *__data, proto))
@@ -591,32 +605,32 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
#define DECLARE_EVENT_CLASS(name, proto, args, tstruct, assign, print)
#define DEFINE_EVENT(template, name, proto, args) \
- DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
+ DECLARE_TRACE_EVENT(name, PARAMS(proto), PARAMS(args))
#define DEFINE_EVENT_FN(template, name, proto, args, reg, unreg)\
- DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
+ DECLARE_TRACE_EVENT(name, PARAMS(proto), PARAMS(args))
#define DEFINE_EVENT_PRINT(template, name, proto, args, print) \
- DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
+ DECLARE_TRACE_EVENT(name, PARAMS(proto), PARAMS(args))
#define DEFINE_EVENT_CONDITION(template, name, proto, \
args, cond) \
- DECLARE_TRACE_CONDITION(name, PARAMS(proto), \
+ DECLARE_TRACE_EVENT_CONDITION(name, PARAMS(proto), \
PARAMS(args), PARAMS(cond))
#define TRACE_EVENT(name, proto, args, struct, assign, print) \
- DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
+ DECLARE_TRACE_EVENT(name, PARAMS(proto), PARAMS(args))
#define TRACE_EVENT_FN(name, proto, args, struct, \
assign, print, reg, unreg) \
- DECLARE_TRACE(name, PARAMS(proto), PARAMS(args))
-#define TRACE_EVENT_FN_COND(name, proto, args, cond, struct, \
+ DECLARE_TRACE_EVENT(name, PARAMS(proto), PARAMS(args))
+#define TRACE_EVENT_FN_COND(name, proto, args, cond, struct, \
assign, print, reg, unreg) \
- DECLARE_TRACE_CONDITION(name, PARAMS(proto), \
+ DECLARE_TRACE_EVENT_CONDITION(name, PARAMS(proto), \
PARAMS(args), PARAMS(cond))
#define TRACE_EVENT_CONDITION(name, proto, args, cond, \
struct, assign, print) \
- DECLARE_TRACE_CONDITION(name, PARAMS(proto), \
+ DECLARE_TRACE_EVENT_CONDITION(name, PARAMS(proto), \
PARAMS(args), PARAMS(cond))
#define TRACE_EVENT_SYSCALL(name, proto, args, struct, assign, \
print, reg, unreg) \
- DECLARE_TRACE_SYSCALL(name, PARAMS(proto), PARAMS(args))
+ DECLARE_TRACE_EVENT_SYSCALL(name, PARAMS(proto), PARAMS(args))
#define TRACE_EVENT_FLAGS(event, flag)
diff --git a/include/trace/bpf_probe.h b/include/trace/bpf_probe.h
index 183fa2aa2935..9391d54d3f12 100644
--- a/include/trace/bpf_probe.h
+++ b/include/trace/bpf_probe.h
@@ -119,14 +119,14 @@ static inline void bpf_test_buffer_##call(void) \
#undef DECLARE_TRACE
#define DECLARE_TRACE(call, proto, args) \
- __BPF_DECLARE_TRACE(call, PARAMS(proto), PARAMS(args)) \
- __DEFINE_EVENT(call, call, PARAMS(proto), PARAMS(args), 0)
+ __BPF_DECLARE_TRACE(call##_tp, PARAMS(proto), PARAMS(args)) \
+ __DEFINE_EVENT(call##_tp, call##_tp, PARAMS(proto), PARAMS(args), 0)
#undef DECLARE_TRACE_WRITABLE
#define DECLARE_TRACE_WRITABLE(call, proto, args, size) \
__CHECK_WRITABLE_BUF_SIZE(call, PARAMS(proto), PARAMS(args), size) \
- __BPF_DECLARE_TRACE(call, PARAMS(proto), PARAMS(args)) \
- __DEFINE_EVENT(call, call, PARAMS(proto), PARAMS(args), size)
+ __BPF_DECLARE_TRACE(call##_tp, PARAMS(proto), PARAMS(args)) \
+ __DEFINE_EVENT(call##_tp, call##_tp, PARAMS(proto), PARAMS(args), size)
#include TRACE_INCLUDE(TRACE_INCLUDE_FILE)
diff --git a/include/trace/define_trace.h b/include/trace/define_trace.h
index ed52d0506c69..b2ba5a80583f 100644
--- a/include/trace/define_trace.h
+++ b/include/trace/define_trace.h
@@ -74,10 +74,18 @@
#undef DECLARE_TRACE
#define DECLARE_TRACE(name, proto, args) \
- DEFINE_TRACE(name, PARAMS(proto), PARAMS(args))
+ DEFINE_TRACE(name##_tp, PARAMS(proto), PARAMS(args))
#undef DECLARE_TRACE_CONDITION
#define DECLARE_TRACE_CONDITION(name, proto, args, cond) \
+ DEFINE_TRACE(name##_tp, PARAMS(proto), PARAMS(args))
+
+#undef DECLARE_TRACE_EVENT
+#define DECLARE_TRACE_EVENT(name, proto, args) \
+ DEFINE_TRACE(name, PARAMS(proto), PARAMS(args))
+
+#undef DECLARE_TRACE_EVENT_CONDITION
+#define DECLARE_TRACE_EVENT_CONDITION(name, proto, args, cond) \
DEFINE_TRACE(name, PARAMS(proto), PARAMS(args))
/* If requested, create helpers for calling these tracepoints from Rust. */
@@ -115,6 +123,11 @@
#undef DECLARE_TRACE_CONDITION
#define DECLARE_TRACE_CONDITION(name, proto, args, cond)
+#undef DECLARE_TRACE_EVENT
+#define DECLARE_TRACE_EVENT(name, proto, args)
+#undef DECLARE_TRACE_EVENT_CONDITION
+#define DECLARE_TRACE_EVENT_CONDITION(name, proto, args, cond)
+
#ifdef TRACEPOINTS_ENABLED
#include <trace/trace_events.h>
#include <trace/perf.h>
@@ -136,6 +149,8 @@
#undef TRACE_HEADER_MULTI_READ
#undef DECLARE_TRACE
#undef DECLARE_TRACE_CONDITION
+#undef DECLARE_TRACE_EVENT
+#undef DECLARE_TRACE_EVENT_CONDITION
/* Only undef what we defined in this file */
#ifdef UNDEF_TRACE_INCLUDE_FILE
diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index 8994e97d86c1..152fc8b37aa5 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -773,64 +773,64 @@ TRACE_EVENT(sched_wake_idle_without_ipi,
*
* Postfixed with _tp to make them easily identifiable in the code.
*/
-DECLARE_TRACE(pelt_cfs_tp,
+DECLARE_TRACE(pelt_cfs,
TP_PROTO(struct cfs_rq *cfs_rq),
TP_ARGS(cfs_rq));
-DECLARE_TRACE(pelt_rt_tp,
+DECLARE_TRACE(pelt_rt,
TP_PROTO(struct rq *rq),
TP_ARGS(rq));
-DECLARE_TRACE(pelt_dl_tp,
+DECLARE_TRACE(pelt_dl,
TP_PROTO(struct rq *rq),
TP_ARGS(rq));
-DECLARE_TRACE(pelt_hw_tp,
+DECLARE_TRACE(pelt_hw,
TP_PROTO(struct rq *rq),
TP_ARGS(rq));
-DECLARE_TRACE(pelt_irq_tp,
+DECLARE_TRACE(pelt_irq,
TP_PROTO(struct rq *rq),
TP_ARGS(rq));
-DECLARE_TRACE(pelt_se_tp,
+DECLARE_TRACE(pelt_se,
TP_PROTO(struct sched_entity *se),
TP_ARGS(se));
-DECLARE_TRACE(sched_cpu_capacity_tp,
+DECLARE_TRACE(sched_cpu_capacity,
TP_PROTO(struct rq *rq),
TP_ARGS(rq));
-DECLARE_TRACE(sched_overutilized_tp,
+DECLARE_TRACE(sched_overutilized,
TP_PROTO(struct root_domain *rd, bool overutilized),
TP_ARGS(rd, overutilized));
-DECLARE_TRACE(sched_util_est_cfs_tp,
+DECLARE_TRACE(sched_util_est_cfs,
TP_PROTO(struct cfs_rq *cfs_rq),
TP_ARGS(cfs_rq));
-DECLARE_TRACE(sched_util_est_se_tp,
+DECLARE_TRACE(sched_util_est_se,
TP_PROTO(struct sched_entity *se),
TP_ARGS(se));
-DECLARE_TRACE(sched_update_nr_running_tp,
+DECLARE_TRACE(sched_update_nr_running,
TP_PROTO(struct rq *rq, int change),
TP_ARGS(rq, change));
-DECLARE_TRACE(sched_compute_energy_tp,
+DECLARE_TRACE(sched_compute_energy,
TP_PROTO(struct task_struct *p, int dst_cpu, unsigned long energy,
unsigned long max_util, unsigned long busy_time),
TP_ARGS(p, dst_cpu, energy, max_util, busy_time));
-DECLARE_TRACE(sched_entry_tp,
+DECLARE_TRACE(sched_entry,
TP_PROTO(bool preempt, unsigned long ip),
TP_ARGS(preempt, ip));
-DECLARE_TRACE(sched_exit_tp,
+DECLARE_TRACE(sched_exit,
TP_PROTO(bool is_switch, unsigned long ip),
TP_ARGS(is_switch, ip));
-DECLARE_TRACE_CONDITION(sched_set_state_tp,
+DECLARE_TRACE_CONDITION(sched_set_state,
TP_PROTO(struct task_struct *tsk, int state),
TP_ARGS(tsk, state),
TP_CONDITION(!!(tsk->__state) != !!state));
diff --git a/include/trace/events/tcp.h b/include/trace/events/tcp.h
index 1a40c41ff8c3..4f9fa1b5b89b 100644
--- a/include/trace/events/tcp.h
+++ b/include/trace/events/tcp.h
@@ -259,7 +259,7 @@ TRACE_EVENT(tcp_retransmit_synack,
__entry->saddr_v6, __entry->daddr_v6)
);
-DECLARE_TRACE(tcp_cwnd_reduction_tp,
+DECLARE_TRACE(tcp_cwnd_reduction,
TP_PROTO(const struct sock *sk, int newly_acked_sacked,
int newly_lost, int flag),
TP_ARGS(sk, newly_acked_sacked, newly_lost, flag)
diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod-events.h b/tools/testing/selftests/bpf/test_kmods/bpf_testmod-events.h
index aeef86b3da74..2bac14ef507f 100644
--- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod-events.h
+++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod-events.h
@@ -42,7 +42,7 @@ DECLARE_TRACE(bpf_testmod_test_nullable_bare,
struct sk_buff;
-DECLARE_TRACE(bpf_testmod_test_raw_tp_null,
+DECLARE_TRACE(bpf_testmod_test_raw_null,
TP_PROTO(struct sk_buff *skb),
TP_ARGS(skb)
);
diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
index 3220f1d28697..fd40c1180b09 100644
--- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c
@@ -413,7 +413,7 @@ bpf_testmod_test_read(struct file *file, struct kobject *kobj,
(void)bpf_testmod_test_arg_ptr_to_struct(&struct_arg1_2);
- (void)trace_bpf_testmod_test_raw_tp_null(NULL);
+ (void)trace_bpf_testmod_test_raw_null_tp(NULL);
bpf_testmod_test_struct_ops3();
@@ -431,14 +431,14 @@ bpf_testmod_test_read(struct file *file, struct kobject *kobj,
if (bpf_testmod_loop_test(101) > 100)
trace_bpf_testmod_test_read(current, &ctx);
- trace_bpf_testmod_test_nullable_bare(NULL);
+ trace_bpf_testmod_test_nullable_bare_tp(NULL);
/* Magic number to enable writable tp */
if (len == 64) {
struct bpf_testmod_test_writable_ctx writable = {
.val = 1024,
};
- trace_bpf_testmod_test_writable_bare(&writable);
+ trace_bpf_testmod_test_writable_bare_tp(&writable);
if (writable.early_ret)
return snprintf(buf, len, "%d\n", writable.val);
}
@@ -470,7 +470,7 @@ bpf_testmod_test_write(struct file *file, struct kobject *kobj,
.len = len,
};
- trace_bpf_testmod_test_write_bare(current, &ctx);
+ trace_bpf_testmod_test_write_bare_tp(current, &ctx);
return -EIO; /* always fail */
}
--
2.47.2
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