[PATCH v7 17/20] tracing/remotes: Add poll_ms tracefs file

[Vincent Donnefort <vdonnefort@google.com>]

Add a tracefs file to configure the trace remote polling period. Keep
the default value to 100ms.

Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
---
 kernel/trace/trace_remote.c | 41 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 40 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace_remote.c b/kernel/trace/trace_remote.c
index 0a360690b174..b2547eb117f8 100644
--- a/kernel/trace/trace_remote.c
+++ b/kernel/trace/trace_remote.c
@@ -427,7 +427,8 @@ static void trace_remote_do_poll(struct trace_remote *remote)
 
 	ring_buffer_poll_remote(remote->trace_buffer, RING_BUFFER_ALL_CPUS);
 	yield = trace_remote_do_dmesg(remote);
-	schedule_delayed_work(&remote->poll_work, yield ? 0 : msecs_to_jiffies(remote->poll_ms));
+	schedule_delayed_work(&remote->poll_work,
+			      yield ? 0 : msecs_to_jiffies(READ_ONCE(remote->poll_ms)));
 }
 
 static void __poll_remote(struct work_struct *work)
@@ -1138,6 +1139,40 @@ static int dump_on_panic_show(struct seq_file *s, void *unused)
 }
 DEFINE_TRACE_REMOTE_ATTRIBUTE(dump_on_panic);
 
+static ssize_t poll_ms_write(struct file *filp, const char __user *ubuf, size_t cnt, loff_t *ppos)
+{
+	struct seq_file *seq = filp->private_data;
+	struct trace_remote *remote = seq->private;
+	unsigned int val;
+	int ret;
+
+	ret = kstrtouint_from_user(ubuf, cnt, 10, &val);
+	if (ret)
+		return ret;
+
+	if (!val)
+		return -EINVAL;
+
+	guard(mutex)(&remote->lock);
+
+	if (val < remote->poll_ms && remote->poll_cnt)
+		mod_delayed_work(system_percpu_wq, &remote->poll_work, msecs_to_jiffies(val));
+
+	WRITE_ONCE(remote->poll_ms, val);
+
+	return cnt;
+}
+
+static int poll_ms_show(struct seq_file *s, void *unused)
+{
+	struct trace_remote *remote = s->private;
+
+	seq_printf(s, "%u\n", READ_ONCE(remote->poll_ms));
+
+	return 0;
+}
+DEFINE_TRACE_REMOTE_ATTRIBUTE(poll_ms);
+
 static int trace_remote_init_tracefs(const char *name, struct trace_remote *remote)
 {
 	struct dentry *remote_d, *percpu_d, *d;
@@ -1170,6 +1205,10 @@ static int trace_remote_init_tracefs(const char *name, struct trace_remote *remo
 	if (!d)
 		goto err;
 
+	d = trace_create_file("poll_ms", TRACEFS_MODE_WRITE, remote_d, remote, &poll_ms_fops);
+	if (!d)
+		goto err;
+
 	d = trace_create_file("buffer_size_kb", TRACEFS_MODE_WRITE, remote_d, remote,
 			      &buffer_size_kb_fops);
 	if (!d)
-- 
2.56.0.rc1.310.g51773c2048-goog