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tracing: Fix read blocking on trace_pipe_raw

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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>
This commit is contained in:
Steven Rostedt 2013-02-28 13:44:11 -05:00 committed by Steven Rostedt
parent cc60cdc952
commit b627344fef
1 changed files with 15 additions and 3 deletions
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18
kernel/trace/trace.c
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@ -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;