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Commit cc60cdc9 authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt
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tracing: Fix polling on trace_pipe_raw 



The trace_pipe_raw never implemented polling and this was casing
issues for several utilities. This is now implemented.

Blocked reads still are on the TODO list.

Reported-by: default avatarMauro Carvalho Chehab <mchehab@redhat.com>
Tested-by: default avatarMauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 189e5784

kernel/trace/trace.c

+51 −27
Original line number Diff line number Diff line
@@ -3555,10 +3555,8 @@ static int tracing_release_pipe(struct inode *inode, struct file *file) 
}



static unsigned int

tracing_poll_pipe(struct file *filp, poll_table *poll_table)

trace_poll(struct trace_iterator *iter, struct file *filp, poll_table *poll_table)

{

	struct trace_iterator *iter = filp->private_data;



	if (trace_flags & TRACE_ITER_BLOCK) {

		/*

		 * Always select as readable when in blocking mode
@@ -3567,6 +3565,7 @@ tracing_poll_pipe(struct file *filp, poll_table *poll_table) 
	} else {

		if (!trace_empty(iter))

			return POLLIN | POLLRDNORM;

		trace_wakeup_needed = true;

		poll_wait(filp, &trace_wait, poll_table);

		if (!trace_empty(iter))

			return POLLIN | POLLRDNORM;
@@ -3575,6 +3574,14 @@ tracing_poll_pipe(struct file *filp, poll_table *poll_table) 
	}

}



static unsigned int

tracing_poll_pipe(struct file *filp, poll_table *poll_table)

{

	struct trace_iterator *iter = filp->private_data;



	return trace_poll(iter, filp, poll_table);

}



/*

 * This is a make-shift waitqueue.

 * A tracer might use this callback on some rare cases:
@@ -4362,9 +4369,8 @@ static const struct file_operations snapshot_fops = { 
#endif /* CONFIG_TRACER_SNAPSHOT */



struct ftrace_buffer_info {

	struct trace_array	*tr;

	struct trace_iterator	iter;

	void			*spare;

	int			cpu;

	unsigned int		read;

};
@@ -4381,8 +4387,8 @@ static int tracing_buffers_open(struct inode *inode, struct file *filp) 
	if (!info)

		return -ENOMEM;



	info->tr	= tr;

	info->cpu	= tc->cpu;

	info->iter.tr		= tr;

	info->iter.cpu_file	= tc->cpu;

	info->spare		= NULL;

	/* Force reading ring buffer for first read */

	info->read		= (unsigned int)-1;
@@ -4392,11 +4398,21 @@ static int tracing_buffers_open(struct inode *inode, struct file *filp) 
	return nonseekable_open(inode, filp);

}



static unsigned int

tracing_buffers_poll(struct file *filp, poll_table *poll_table)

{

	struct ftrace_buffer_info *info = filp->private_data;

	struct trace_iterator *iter = &info->iter;



	return trace_poll(iter, filp, poll_table);

}



static ssize_t

tracing_buffers_read(struct file *filp, char __user *ubuf,

		     size_t count, loff_t *ppos)

{

	struct ftrace_buffer_info *info = filp->private_data;

	struct trace_iterator *iter = &info->iter;

	ssize_t ret;

	size_t size;
@@ -4404,7 +4420,7 @@ tracing_buffers_read(struct file *filp, char __user *ubuf, 
		return 0;



	if (!info->spare)

		info->spare = ring_buffer_alloc_read_page(info->tr->buffer, info->cpu);

		info->spare = ring_buffer_alloc_read_page(iter->tr->buffer, iter->cpu_file);

	if (!info->spare)

		return -ENOMEM;
@@ -4412,12 +4428,12 @@ tracing_buffers_read(struct file *filp, char __user *ubuf, 
	if (info->read < PAGE_SIZE)

		goto read;



	trace_access_lock(info->cpu);

	ret = ring_buffer_read_page(info->tr->buffer,

	trace_access_lock(iter->cpu_file);

	ret = ring_buffer_read_page(iter->tr->buffer,

				    &info->spare,

				    count,

				    info->cpu, 0);

	trace_access_unlock(info->cpu);

				    iter->cpu_file, 0);

	trace_access_unlock(iter->cpu_file);

	if (ret < 0)

		return 0;
@@ -4442,9 +4458,10 @@ read: 
static int tracing_buffers_release(struct inode *inode, struct file *file)

{

	struct ftrace_buffer_info *info = file->private_data;

	struct trace_iterator *iter = &info->iter;



	if (info->spare)

		ring_buffer_free_read_page(info->tr->buffer, info->spare);

		ring_buffer_free_read_page(iter->tr->buffer, info->spare);

	kfree(info);



	return 0;
@@ -4511,6 +4528,7 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos, 
			    unsigned int flags)

{

	struct ftrace_buffer_info *info = file->private_data;

	struct trace_iterator *iter = &info->iter;

	struct partial_page partial_def[PIPE_DEF_BUFFERS];

	struct page *pages_def[PIPE_DEF_BUFFERS];

	struct splice_pipe_desc spd = {
@@ -4541,8 +4559,9 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos, 
		len &= PAGE_MASK;

	}



	trace_access_lock(info->cpu);

	entries = ring_buffer_entries_cpu(info->tr->buffer, info->cpu);

 again:

	trace_access_lock(iter->cpu_file);

	entries = ring_buffer_entries_cpu(iter->tr->buffer, iter->cpu_file);



	for (i = 0; i < pipe->buffers && len && entries; i++, len -= PAGE_SIZE) {

		struct page *page;
@@ -4553,15 +4572,15 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos, 
			break;



		ref->ref = 1;

		ref->buffer = info->tr->buffer;

		ref->page = ring_buffer_alloc_read_page(ref->buffer, info->cpu);

		ref->buffer = iter->tr->buffer;

		ref->page = ring_buffer_alloc_read_page(ref->buffer, iter->cpu_file);

		if (!ref->page) {

			kfree(ref);

			break;

		}



		r = ring_buffer_read_page(ref->buffer, &ref->page,

					  len, info->cpu, 1);

					  len, iter->cpu_file, 1);

		if (r < 0) {

			ring_buffer_free_read_page(ref->buffer, ref->page);

			kfree(ref);
@@ -4585,21 +4604,25 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos, 
		spd.nr_pages++;

		*ppos += PAGE_SIZE;



		entries = ring_buffer_entries_cpu(info->tr->buffer, info->cpu);

		entries = ring_buffer_entries_cpu(iter->tr->buffer, iter->cpu_file);

	}



	trace_access_unlock(info->cpu);

	trace_access_unlock(iter->cpu_file);

	spd.nr_pages = i;



	/* did we read anything? */

	if (!spd.nr_pages) {

		if ((file->f_flags & O_NONBLOCK) || (flags & SPLICE_F_NONBLOCK))

		if ((file->f_flags & O_NONBLOCK) || (flags & SPLICE_F_NONBLOCK)) {

			ret = -EAGAIN;

		else

			ret = 0;

		/* TODO: block */

			goto out;

		}

		default_wait_pipe(iter);

		if (signal_pending(current)) {

			ret = -EINTR;

			goto out;

		}

		goto again;

	}



	ret = splice_to_pipe(pipe, &spd);

	splice_shrink_spd(&spd);
@@ -4610,6 +4633,7 @@ out: 
static const struct file_operations tracing_buffers_fops = {

	.open		= tracing_buffers_open,

	.read		= tracing_buffers_read,

	.poll		= tracing_buffers_poll,

	.release	= tracing_buffers_release,

	.splice_read	= tracing_buffers_splice_read,

	.llseek		= no_llseek,