Commit b627344f authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt
Browse files

tracing: Fix read blocking on trace_pipe_raw

If the ring buffer is empty, a read to trace_pipe_raw wont block.
The tracing code has the infrastructure to wake up waiting readers,
but the trace_pipe_raw doesn't take advantage of that.

When a read is done to trace_pipe_raw without the O_NONBLOCK flag
set, have the read block until there's data in the requested buffer.
Signed-off-by: default avatarSteven Rostedt <>
parent cc60cdc9
......@@ -4389,6 +4389,7 @@ static int tracing_buffers_open(struct inode *inode, struct file *filp)
info-> = tr;
info->iter.cpu_file = tc->cpu;
info->iter.trace = tr->current_trace;
info->spare = NULL;
/* Force reading ring buffer for first read */
info->read = (unsigned int)-1;
......@@ -4428,18 +4429,29 @@ tracing_buffers_read(struct file *filp, char __user *ubuf,
if (info->read < PAGE_SIZE)
goto read;
ret = ring_buffer_read_page(iter->tr->buffer,
iter->cpu_file, 0);
if (ret < 0)
if (ret < 0) {
if (trace_empty(iter)) {
if ((filp->f_flags & O_NONBLOCK))
return -EAGAIN;
if (signal_pending(current))
return -EINTR;
goto again;
return 0;
info->read = 0;
size = PAGE_SIZE - info->read;
if (size > count)
size = count;
......@@ -4616,7 +4628,7 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
ret = -EAGAIN;
goto out;
if (signal_pending(current)) {
ret = -EINTR;
goto out;
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