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Message-ID: <20251003133825.2068970-7-vdonnefort@google.com>
Date: Fri, 3 Oct 2025 14:38:03 +0100
From: Vincent Donnefort <vdonnefort@...gle.com>
To: rostedt@...dmis.org, mhiramat@...nel.org, mathieu.desnoyers@...icios.com,
linux-trace-kernel@...r.kernel.org, maz@...nel.org, oliver.upton@...ux.dev,
joey.gouly@....com, suzuki.poulose@....com, yuzenghui@...wei.com
Cc: kvmarm@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
jstultz@...gle.com, qperret@...gle.com, will@...nel.org,
aneesh.kumar@...nel.org, kernel-team@...roid.com,
linux-kernel@...r.kernel.org, Vincent Donnefort <vdonnefort@...gle.com>
Subject: [PATCH v7 06/28] tracing: Add reset to trace remotes
Allow to reset the trace remote buffer by writing to the Tracefs "trace"
file. This is similar to the regular Tracefs interface.
Signed-off-by: Vincent Donnefort <vdonnefort@...gle.com>
diff --git a/include/linux/trace_remote.h b/include/linux/trace_remote.h
index feb3433c2128..55754ef78104 100644
--- a/include/linux/trace_remote.h
+++ b/include/linux/trace_remote.h
@@ -18,6 +18,8 @@
* remote to allow writing.
* @swap_reader_page: Called when Tracefs consumes a new page from a
* ring-buffer. It is expected from the remote to isolate a
+ * @reset: Called on `echo 0 > trace`. It is expected from the
+ * remote to reset all ring-buffer pages.
* new reader-page from the @cpu ring-buffer.
*/
struct trace_remote_callbacks {
@@ -25,6 +27,7 @@ struct trace_remote_callbacks {
void (*unload_trace_buffer)(struct trace_buffer_desc *desc, void *priv);
int (*enable_tracing)(bool enable, void *priv);
int (*swap_reader_page)(unsigned int cpu, void *priv);
+ int (*reset)(unsigned int cpu, void *priv);
};
/**
diff --git a/kernel/trace/trace_remote.c b/kernel/trace/trace_remote.c
index 3d76a4d7d5f5..abf83ff75df5 100644
--- a/kernel/trace/trace_remote.c
+++ b/kernel/trace/trace_remote.c
@@ -63,6 +63,7 @@ static int trace_remote_load(struct trace_remote *remote)
rb_remote->desc = remote->trace_buffer_desc;
rb_remote->swap_reader_page = remote->cbs->swap_reader_page;
rb_remote->priv = remote->priv;
+ rb_remote->reset = remote->cbs->reset;
remote->trace_buffer = ring_buffer_alloc_remote(rb_remote);
if (!remote->trace_buffer) {
remote->cbs->unload_trace_buffer(remote->trace_buffer_desc, remote->priv);
@@ -136,6 +137,21 @@ static int trace_remote_disable_tracing(struct trace_remote *remote)
return 0;
}
+static void trace_remote_reset(struct trace_remote *remote, int cpu)
+{
+ lockdep_assert_held(&remote->lock);
+
+ if (!trace_remote_loaded(remote))
+ return;
+
+ if (cpu == RING_BUFFER_ALL_CPUS)
+ ring_buffer_reset(remote->trace_buffer);
+ else
+ ring_buffer_reset_cpu(remote->trace_buffer, cpu);
+
+ trace_remote_try_unload(remote);
+}
+
static ssize_t
tracing_on_write(struct file *filp, const char __user *ubuf, size_t cnt, loff_t *ppos)
{
@@ -411,6 +427,26 @@ static const struct file_operations trace_pipe_fops = {
.release = trace_pipe_release,
};
+static ssize_t trace_write(struct file *filp, const char __user *ubuf, size_t cnt, loff_t *ppos)
+{
+ struct inode *inode = file_inode(filp);
+ struct trace_remote *remote = inode->i_private;
+ int cpu = RING_BUFFER_ALL_CPUS;
+
+ if (inode->i_cdev)
+ cpu = (long)inode->i_cdev - 1;
+
+ guard(mutex)(&remote->lock);
+
+ trace_remote_reset(remote, cpu);
+
+ return cnt;
+}
+
+static const struct file_operations trace_fops = {
+ .write = trace_write,
+};
+
static int trace_remote_init_tracefs(const char *name, struct trace_remote *remote)
{
struct dentry *remote_d, *percpu_d;
@@ -441,7 +477,9 @@ static int trace_remote_init_tracefs(const char *name, struct trace_remote *remo
!trace_create_file("buffer_size_kb", TRACEFS_MODE_WRITE, remote_d, remote,
&buffer_size_kb_fops) ||
!trace_create_file("trace_pipe", TRACEFS_MODE_READ, remote_d, remote,
- &trace_pipe_fops))
+ &trace_pipe_fops) ||
+ !trace_create_file("trace", TRACEFS_MODE_WRITE, remote_d, remote,
+ &trace_fops))
goto err;
percpu_d = tracefs_create_dir("per_cpu", remote_d);
@@ -463,7 +501,9 @@ static int trace_remote_init_tracefs(const char *name, struct trace_remote *remo
}
if (!trace_create_cpu_file("trace_pipe", TRACEFS_MODE_READ, cpu_d, remote, cpu,
- &trace_pipe_fops))
+ &trace_pipe_fops) ||
+ !trace_create_cpu_file("trace", TRACEFS_MODE_WRITE, cpu_d, remote, cpu,
+ &trace_fops))
goto err;
}
--
2.51.0.618.g983fd99d29-goog
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