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Subject: Re: [PATCH 3/3] tracing: poll-able ring_buffer consumer
From: Steven Rostedt <rostedt@goodmis.org>
Reply-To: rostedt@goodmis.org
To: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Ingo Molnar <mingo@elte.hu>, Frederic Weisbecker <fweisbec@gmail.com>,
       LKML <linux-kernel@vger.kernel.org>
In-Reply-To: <4A95F78F.8010307@cn.fujitsu.com>
References: <4A95F78F.8010307@cn.fujitsu.com>
Content-Type: text/plain
Organization: Kihon Technologies Inc.
Date: Wed, 09 Sep 2009 17:12:29 -0400
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On Thu, 2009-08-27 at 11:03 +0800, Lai Jiangshan wrote:
> makes consumer side(per_cpu/cpu#/trace_pipe_raw) poll-able
> 
> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
> ---
> diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
> index b81ceed..6fd2664 100644
> --- a/include/linux/ring_buffer.h
> +++ b/include/linux/ring_buffer.h
> @@ -4,6 +4,7 @@
>  #include <linux/kmemcheck.h>
>  #include <linux/mm.h>
>  #include <linux/seq_file.h>
> +#include <linux/poll.h>
>  
>  struct ring_buffer;
>  struct ring_buffer_iter;
> @@ -188,6 +189,8 @@ int ring_buffer_read_page(struct ring_buffer *buffer, void **data_page,
>  void ring_buffer_notify(struct ring_buffer *buffer);
>  signed long ring_buffer_wait_page(struct ring_buffer *buffer, int cpu,
>  		signed long timeout);
> +unsigned int ring_buffer_poll(struct ring_buffer *buffer, int cpu,
> +		struct file *filp, poll_table *poll_table);
>  
>  struct trace_seq;
>  
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index db82b38..c7c23da 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -3389,6 +3389,22 @@ ring_buffer_wait_page(struct ring_buffer *buffer, int cpu, signed long timeout)
>  			rb_page_available(cpu_buffer), timeout);
>  }
>  

/**
 * ring_buffer_poll --- COMMENT ME ;-)
...

> +unsigned int ring_buffer_poll(struct ring_buffer *buffer, int cpu,
> +		struct file *filp, poll_table *poll_table)
> +{
> +	struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
> +
> +	if (rb_page_available(cpu_buffer))
> +		return POLLIN | POLLRDNORM;
> +
> +	poll_wait(filp, &cpu_buffer->sleepers, poll_table);
> +
> +	if (rb_page_available(cpu_buffer))
> +		return POLLIN | POLLRDNORM;
> +
> +	return 0;
> +}
> +
>  /**
>   * ring_buffer_size - return the size of the ring buffer (in bytes)
>   * @buffer: The ring buffer.
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index ee435ed..c2aa14c 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -3294,6 +3294,14 @@ static int tracing_buffers_release(struct inode *inode, struct file *file)
>  	return 0;
>  }
>  
> +static
> +unsigned int tracing_buffers_poll(struct file *filp, poll_table *poll_table)
> +{
> +	struct ftrace_buffer_info *info = filp->private_data;
> +
> +	return ring_buffer_poll(info->tr->buffer, info->cpu, filp, poll_table);
> +}
> +
>  struct buffer_ref {
>  	struct ring_buffer	*buffer;
>  	void			*page;
> @@ -3459,6 +3467,7 @@ static const struct file_operations tracing_buffers_fops = {
>  	.open		= tracing_buffers_open,
>  	.read		= tracing_buffers_read,
>  	.release	= tracing_buffers_release,
> +	.poll		= tracing_buffers_poll,
>  	.splice_read	= tracing_buffers_splice_read,
>  	.llseek		= no_llseek,
>  };

I'm fine with this patch. (besides the missing comment)

-- Steve