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: Steven Rostedt <rostedt@goodmis.org>
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 4a6e461..3ec146c 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4389,6 +4389,7 @@
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;
@@ -4428,18 +4429,29 @@
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;
@@ -4616,7 +4628,7 @@
ret = -EAGAIN;
goto out;
}
- default_wait_pipe(iter);
+ iter->trace->wait_pipe(iter);
if (signal_pending(current)) {
ret = -EINTR;
goto out;