Re: [RFC Patch 1/1] debugfs_printk and debugfs_dump interface

From: Randy Dunlap
Date: Mon Apr 21 2008 - 13:30:53 EST


On Mon, 21 Apr 2008 18:13:29 +0530 K. Prasad wrote:

> This patch introduces two new interfaces called debugfs_printk and
> debugfs_dump which can be used to print to the debugfs mount directly.
> It uses the 'trace' infrastructure underneath and is a patch over it.
> A sample file is also created to demonstrate its ease of use.
>
> Signed-off-by: K.Prasad <prasad@xxxxxxxxxxxxxxxxxx>
> ---
> Documentation/trace.txt | 21 ++++
> include/linux/trace.h | 55 +++++++++++
> lib/trace.c | 196 +++++++++++++++++++++++++++++++++++++++--
> samples/trace/Makefile | 2
> samples/trace/fork_new_trace.c | 97 ++++++++++++++++++++
> 5 files changed, 365 insertions(+), 6 deletions(-)

> Index: linux-2.6.25-rc8-mm1/lib/trace.c
> ===================================================================
> --- linux-2.6.25-rc8-mm1.orig/lib/trace.c
> +++ linux-2.6.25-rc8-mm1/lib/trace.c
> @@ -561,3 +609,141 @@ void trace_cleanup(struct trace_info *tr
> kfree(trace);
> }
> EXPORT_SYMBOL_GPL(trace_cleanup);
> +
> +/**
> + * trace_cleanup_all - Removes all trace_info/directories created under a
> + * parent_dir

kernel-doc requires the "function name - description" to be on one line.
You could change the *<tab> to be *<space(s)>.

> + * @parent_dir: Name of the parent directory
> + */
> +void trace_cleanup_all(const char *parent_dir)
> +{
> + struct list_head *pos, *pos_temp;
> + struct trace_dir *temp;
> +
> + list_for_each_safe(pos, pos_temp, &trace_dirs) {
> + temp = list_entry(pos, struct trace_dir, trace_dir_list);
> + if (!strcmp(parent_dir, temp->trace_root->d_iname))
> + trace_cleanup(temp->ti);
> + }
> +}
> +EXPORT_SYMBOL_GPL(trace_cleanup_all);
> +
...
> +
> +/*
> + * debugfs_printk - A function to write into the debugfs mount 'directly'
> + * using 'trace' infrastructure
> + * @dpk - Structure containing info such as parent_dir and directory
> + * @format - String containing format string specifiers
> + * @ap - List of arguments

This one isn't quite kernel-doc notation, but it's very close to it,
and it should be kernel-doc since it's an exported symbol.
So it needs the following changes:

- begin with /**
- put function name + short description on one line
- use "@dpk: <description>" for function parameters (not "-")

> + */
> +int debugfs_printk(struct debugfs_printk_data *dpk, char *format, ...)
> +{
> + int ret;
> + struct trace_info *ti;
> + va_list(ap);
> + unsigned long flags;
> +
> + va_start(ap, format);
> +
> + ti = init_trace_interface(dpk);
> +
> + /* Now do the actual printing */
> + /* Take an RCU Lock over the trace_info state */
> + rcu_read_lock();
> + /* Take a spinlock for the global buffer used by relay */
> + if (dpk->flags & TRACE_GLOBAL_CHANNEL)
> + spin_lock_irqsave(&trace_lock, flags);
> + ret = trace_printf(ti, format, ap);
> + if (dpk->flags & TRACE_GLOBAL_CHANNEL)
> + spin_unlock_irqrestore(&trace_lock, flags);
> + rcu_read_unlock();
> +
> + va_end(ap);
> + return ret;
> +}
> +EXPORT_SYMBOL(debugfs_printk);
> +
> +/*
> + * debugfs_printk - A function to write into the debugfs mount 'directly'
> + * using 'trace' infrastructure
> + * @dpk - Structure containing info such as parent_dir and directory
> + * @output - Data that needs to be output
> + * @output_len - Length of the output data

Use kernel-doc notation. Same comments as above.

> + */
> +int debugfs_dump(struct debugfs_printk_data *dpk, const void *output,
> + const int output_len)
> +{
> + struct trace_info *ti;
> + char *record;
> +
> + ti = init_trace_interface(dpk);
> +
> + /* Now do the actual printing */
> + rcu_read_lock();
> + record = relay_reserve(ti->rchan, output_len);
> + if (record)
> + memcpy(record, output, output_len);
> + else
> + return -ENOMEM;
> + rcu_read_unlock();
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(debugfs_dump);

> Index: linux-2.6.25-rc8-mm1/Documentation/trace.txt
> ===================================================================
> --- linux-2.6.25-rc8-mm1.orig/Documentation/trace.txt
> +++ linux-2.6.25-rc8-mm1/Documentation/trace.txt
> @@ -150,6 +150,27 @@ The steps a kernel data provider takes t
> 5) Destroy the trace channel and underlying relay channel -
> trace_cleanup().
>
> +Alternatively the user may choose to make use of two new interfaces

two new interfaces --

> +debugfs_printk() and debugfs_dump() to setup trace interface and

and debugfs_dump() -- to setup trace interfaces and

> +trace_cleanup_all() to tear-down the same.
> +
> +Steps to use:


---
~Randy
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