From: Steven Rostedt <srostedt@redhat.com>
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: Steven Rostedt <rostedt@goodmis.org>
---
kernel/trace/trace.c | 18 +++++++++++++++---
1 file changed, 15 insertions(+), 3 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index b958e9d..32b003c 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4339,6 +4339,7 @@ static int tracing_buffers_open(struct inode *inode, struct file *filp)
info->iter.tr = 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;
@@ -4378,18 +4379,29 @@ tracing_buffers_read(struct file *filp, char __user *ubuf,
if (info->read < PAGE_SIZE)
goto read;
+ again:
trace_access_lock(iter->cpu_file);
ret = ring_buffer_read_page(iter->tr->buffer,
&info->spare,
count,
iter->cpu_file, 0);
trace_access_unlock(iter->cpu_file);
- if (ret < 0)
+
+ if (ret < 0) {
+ if (trace_empty(iter)) {
+ if ((filp->f_flags & O_NONBLOCK))
+ return -EAGAIN;
+ iter->trace->wait_pipe(iter);
+ if (signal_pending(current))
+ return -EINTR;
+ goto again;
+ }
return 0;
+ }
info->read = 0;
-read:
+ read:
size = PAGE_SIZE - info->read;
if (size > count)
size = count;
@@ -4566,7 +4578,7 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
ret = -EAGAIN;
goto out;
}
- default_wait_pipe(iter);
+ iter->trace->wait_pipe(iter);
if (signal_pending(current)) {
ret = -EINTR;
goto out;
--
1.7.10.4
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/