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Subject[PATCH 3/3] tracing: poll-able ring_buffer consumer

makes consumer side(per_cpu/cpu#/trace_pipe_raw) poll-able

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
index b81ceed..6fd2664 100644
--- a/include/linux/ring_buffer.h
+++ b/include/linux/ring_buffer.h
@@ -4,6 +4,7 @@
#include <linux/kmemcheck.h>
#include <linux/mm.h>
#include <linux/seq_file.h>
+#include <linux/poll.h>

struct ring_buffer;
struct ring_buffer_iter;
@@ -188,6 +189,8 @@ int ring_buffer_read_page(struct ring_buffer *buffer, void **data_page,
void ring_buffer_notify(struct ring_buffer *buffer);
signed long ring_buffer_wait_page(struct ring_buffer *buffer, int cpu,
signed long timeout);
+unsigned int ring_buffer_poll(struct ring_buffer *buffer, int cpu,
+ struct file *filp, poll_table *poll_table);

struct trace_seq;

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index db82b38..c7c23da 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -3389,6 +3389,22 @@ ring_buffer_wait_page(struct ring_buffer *buffer, int cpu, signed long timeout)
rb_page_available(cpu_buffer), timeout);
}

+unsigned int ring_buffer_poll(struct ring_buffer *buffer, int cpu,
+ struct file *filp, poll_table *poll_table)
+{
+ struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
+
+ if (rb_page_available(cpu_buffer))
+ return POLLIN | POLLRDNORM;
+
+ poll_wait(filp, &cpu_buffer->sleepers, poll_table);
+
+ if (rb_page_available(cpu_buffer))
+ return POLLIN | POLLRDNORM;
+
+ return 0;
+}
+
/**
* ring_buffer_size - return the size of the ring buffer (in bytes)
* @buffer: The ring buffer.
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index ee435ed..c2aa14c 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3294,6 +3294,14 @@ static int tracing_buffers_release(struct inode *inode, struct file *file)
return 0;
}

+static
+unsigned int tracing_buffers_poll(struct file *filp, poll_table *poll_table)
+{
+ struct ftrace_buffer_info *info = filp->private_data;
+
+ return ring_buffer_poll(info->tr->buffer, info->cpu, filp, poll_table);
+}
+
struct buffer_ref {
struct ring_buffer *buffer;
void *page;
@@ -3459,6 +3467,7 @@ static const struct file_operations tracing_buffers_fops = {
.open = tracing_buffers_open,
.read = tracing_buffers_read,
.release = tracing_buffers_release,
+ .poll = tracing_buffers_poll,
.splice_read = tracing_buffers_splice_read,
.llseek = no_llseek,
};




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