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Message-ID: <20250802162829.198364711@kernel.org>
Date: Sat, 02 Aug 2025 12:27:36 -0400
From: Steven Rostedt <rostedt@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: Tomas Glozar <tglozar@...hat.com>,
John Kacur <jkacur@...hat.com>,
Masami Hiramatsu <mhiramat@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: [for-next][PATCH 2/6] tracing: Add guard(ring_buffer_nest)
From: Steven Rostedt <rostedt@...dmis.org>
Some calls to the tracing ring buffer can happen when the ring buffer is
already being written to by the same context (for example, a
trace_printk() in between a ring_buffer_lock_reserve() and a
ring_buffer_unlock_commit()).
In order to not trigger the recursion detection, these functions use
ring_buffer_nest_start() and ring_buffer_nest_end(). Create a guard() for
these functions so that their use cases can be simplified and not need to
use goto for the release.
Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Link: https://lore.kernel.org/20250801203857.710501021@kernel.org
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
include/linux/ring_buffer.h | 3 ++
kernel/trace/trace.c | 69 +++++++++++++------------------
kernel/trace/trace_events_synth.c | 6 +--
3 files changed, 34 insertions(+), 44 deletions(-)
diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
index cd7f0ae26615..8253cb69540c 100644
--- a/include/linux/ring_buffer.h
+++ b/include/linux/ring_buffer.h
@@ -144,6 +144,9 @@ int ring_buffer_write(struct trace_buffer *buffer,
void ring_buffer_nest_start(struct trace_buffer *buffer);
void ring_buffer_nest_end(struct trace_buffer *buffer);
+DEFINE_GUARD(ring_buffer_nest, struct trace_buffer *,
+ ring_buffer_nest_start(_T), ring_buffer_nest_end(_T))
+
struct ring_buffer_event *
ring_buffer_peek(struct trace_buffer *buffer, int cpu, u64 *ts,
unsigned long *lost_events);
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 0ec9cab9a812..332487179e1d 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1160,13 +1160,11 @@ int __trace_array_puts(struct trace_array *tr, unsigned long ip,
trace_ctx = tracing_gen_ctx();
buffer = tr->array_buffer.buffer;
- ring_buffer_nest_start(buffer);
+ guard(ring_buffer_nest)(buffer);
event = __trace_buffer_lock_reserve(buffer, TRACE_PRINT, alloc,
trace_ctx);
- if (!event) {
- size = 0;
- goto out;
- }
+ if (!event)
+ return 0;
entry = ring_buffer_event_data(event);
entry->ip = ip;
@@ -1182,8 +1180,6 @@ int __trace_array_puts(struct trace_array *tr, unsigned long ip,
__buffer_unlock_commit(buffer, event);
ftrace_trace_stack(tr, buffer, trace_ctx, 4, NULL);
- out:
- ring_buffer_nest_end(buffer);
return size;
}
EXPORT_SYMBOL_GPL(__trace_array_puts);
@@ -1213,7 +1209,6 @@ int __trace_bputs(unsigned long ip, const char *str)
struct bputs_entry *entry;
unsigned int trace_ctx;
int size = sizeof(struct bputs_entry);
- int ret = 0;
if (!printk_binsafe(tr))
return __trace_puts(ip, str, strlen(str));
@@ -1227,11 +1222,11 @@ int __trace_bputs(unsigned long ip, const char *str)
trace_ctx = tracing_gen_ctx();
buffer = tr->array_buffer.buffer;
- ring_buffer_nest_start(buffer);
+ guard(ring_buffer_nest)(buffer);
event = __trace_buffer_lock_reserve(buffer, TRACE_BPUTS, size,
trace_ctx);
if (!event)
- goto out;
+ return 0;
entry = ring_buffer_event_data(event);
entry->ip = ip;
@@ -1240,10 +1235,7 @@ int __trace_bputs(unsigned long ip, const char *str)
__buffer_unlock_commit(buffer, event);
ftrace_trace_stack(tr, buffer, trace_ctx, 4, NULL);
- ret = 1;
- out:
- ring_buffer_nest_end(buffer);
- return ret;
+ return 1;
}
EXPORT_SYMBOL_GPL(__trace_bputs);
@@ -3397,21 +3389,19 @@ int trace_vbprintk(unsigned long ip, const char *fmt, va_list args)
size = sizeof(*entry) + sizeof(u32) * len;
buffer = tr->array_buffer.buffer;
- ring_buffer_nest_start(buffer);
- event = __trace_buffer_lock_reserve(buffer, TRACE_BPRINT, size,
- trace_ctx);
- if (!event)
- goto out;
- entry = ring_buffer_event_data(event);
- entry->ip = ip;
- entry->fmt = fmt;
-
- memcpy(entry->buf, tbuffer, sizeof(u32) * len);
- __buffer_unlock_commit(buffer, event);
- ftrace_trace_stack(tr, buffer, trace_ctx, 6, NULL);
+ scoped_guard(ring_buffer_nest, buffer) {
+ event = __trace_buffer_lock_reserve(buffer, TRACE_BPRINT, size,
+ trace_ctx);
+ if (!event)
+ goto out_put;
+ entry = ring_buffer_event_data(event);
+ entry->ip = ip;
+ entry->fmt = fmt;
-out:
- ring_buffer_nest_end(buffer);
+ memcpy(entry->buf, tbuffer, sizeof(u32) * len);
+ __buffer_unlock_commit(buffer, event);
+ ftrace_trace_stack(tr, buffer, trace_ctx, 6, NULL);
+ }
out_put:
put_trace_buf();
@@ -3452,20 +3442,19 @@ int __trace_array_vprintk(struct trace_buffer *buffer,
len = vscnprintf(tbuffer, TRACE_BUF_SIZE, fmt, args);
size = sizeof(*entry) + len + 1;
- ring_buffer_nest_start(buffer);
- event = __trace_buffer_lock_reserve(buffer, TRACE_PRINT, size,
- trace_ctx);
- if (!event)
- goto out;
- entry = ring_buffer_event_data(event);
- entry->ip = ip;
-
- memcpy(&entry->buf, tbuffer, len + 1);
- __buffer_unlock_commit(buffer, event);
- ftrace_trace_stack(printk_trace, buffer, trace_ctx, 6, NULL);
+ scoped_guard(ring_buffer_nest, buffer) {
+ event = __trace_buffer_lock_reserve(buffer, TRACE_PRINT, size,
+ trace_ctx);
+ if (!event)
+ goto out;
+ entry = ring_buffer_event_data(event);
+ entry->ip = ip;
+ memcpy(&entry->buf, tbuffer, len + 1);
+ __buffer_unlock_commit(buffer, event);
+ ftrace_trace_stack(printk_trace, buffer, trace_ctx, 6, NULL);
+ }
out:
- ring_buffer_nest_end(buffer);
put_trace_buf();
out_nobuffer:
diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
index 33cfbd4ed76d..f24ee61f8884 100644
--- a/kernel/trace/trace_events_synth.c
+++ b/kernel/trace/trace_events_synth.c
@@ -536,12 +536,12 @@ static notrace void trace_event_raw_event_synth(void *__data,
* is being performed within another event.
*/
buffer = trace_file->tr->array_buffer.buffer;
- ring_buffer_nest_start(buffer);
+ guard(ring_buffer_nest)(buffer);
entry = trace_event_buffer_reserve(&fbuffer, trace_file,
sizeof(*entry) + fields_size);
if (!entry)
- goto out;
+ return;
for (i = 0, n_u64 = 0; i < event->n_fields; i++) {
val_idx = var_ref_idx[i];
@@ -584,8 +584,6 @@ static notrace void trace_event_raw_event_synth(void *__data,
}
trace_event_buffer_commit(&fbuffer);
-out:
- ring_buffer_nest_end(buffer);
}
static void free_synth_event_print_fmt(struct trace_event_call *call)
--
2.47.2
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