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authorSteven Rostedt <srostedt@redhat.com>2013-02-28 13:44:11 -0500
committerSteven Rostedt <rostedt@goodmis.org>2013-03-15 00:34:49 -0400
commitb627344fef0c38fa4e3050348e168e46db87c905 (patch)
treed828a640959fcb39667cbc56cd7cf8e75f34636f /kernel/trace/trace.c
parentcc60cdc952be09bca5b0bff9fefc7aa6185c3049 (diff)
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>
Diffstat (limited to 'kernel/trace/trace.c')
-rw-r--r--kernel/trace/trace.c18
1 files changed, 15 insertions, 3 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 4a6e461273a9..3ec146c96df4 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4389,6 +4389,7 @@ 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;
@@ -4428,18 +4429,29 @@ 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;
@@ -4616,7 +4628,7 @@ 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;