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    Subject[PATCH 25/25] dynamic_debug: add $DBGFS/dynamic_debug/pending
    Date
    add pending file so user can see queries that are pending.
    This needs work - it currently loops through all pending queries,
    but doesnt terminate - it starts over at the beginning.

    Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
    ---
    lib/dynamic_debug.c | 169 ++++++++++++++++++++++++++++++++++++++++++++++++++-
    1 files changed, 168 insertions(+), 1 deletions(-)

    diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
    index 6dbefb7..0f0bc61 100644
    --- a/lib/dynamic_debug.c
    +++ b/lib/dynamic_debug.c
    @@ -65,6 +65,10 @@ struct ddebug_iter {
    unsigned int idx;
    };

    +struct pending_iter {
    + struct pending_query *elem;
    +};
    +
    static DEFINE_MUTEX(ddebug_lock);
    static LIST_HEAD(ddebug_tables);
    static int verbose = 0;
    @@ -948,6 +952,162 @@ static const struct file_operations ddebug_proc_fops = {
    .write = ddebug_proc_write
    };

    +/*
    + * Set the iterator to point to the first pending_query object
    + * and return a pointer to that first object. Returns
    + * NULL if there are no pending_querys at all.
    + */
    +static struct pending_query *pending_iter_first(struct pending_iter *iter)
    +{
    + if (list_empty(&pending_queries))
    + return NULL;
    + iter->elem = list_entry(pending_queries.next,
    + struct pending_query, link);
    + return iter->elem;
    +}
    +
    +/*
    + * Advance the iterator to point to the next pending_query
    + * object from the one the iterator currently points at,
    + * and returns a pointer to the new pending_query. Returns
    + * NULL if the iterator has seen all the pending_querys.
    + */
    +static struct pending_query *pending_iter_next(struct pending_iter *iter)
    +{
    + if (iter->elem == NULL)
    + return NULL;
    + if (list_is_last(&iter->elem->link, &pending_queries)) {
    + iter->elem = NULL;
    + return NULL;
    + }
    + iter->elem = list_entry(iter->elem->link.next,
    + struct pending_query, link);
    + return iter->elem;
    +}
    +
    +/*
    + * Seq_ops start method. Called at the start of every
    + * read() call from userspace. Takes the pending_lock and
    + * seeks the seq_file's iterator to the given position.
    + */
    +static void *pending_proc_start(struct seq_file *m, loff_t *pos)
    +{
    + struct pending_iter *iter = m->private;
    + struct pending_query *pq;
    + int n = *pos;
    +
    + pr_debug("called m=%p *pos=%lld\n", m, (unsigned long long)*pos);
    +
    + mutex_lock(&ddebug_lock);
    +
    + if (!n)
    + return SEQ_START_TOKEN;
    + if (n < 0)
    + return NULL;
    + pq = pending_iter_first(iter);
    + /*while (pq != NULL && --n > 0)
    + pq = pending_iter_next(iter);
    + */
    + return pq;
    +}
    +
    +/*
    + * Seq_ops next method. Called several times within a read()
    + * call from userspace, with pending_lock held. Walks to the
    + * next pending_query object with a special case for the header line.
    + */
    +static void *pending_proc_next(struct seq_file *m, void *p, loff_t *pos)
    +{
    + struct pending_iter *iter = m->private;
    + struct pending_query *pq;
    +
    + pr_debug("called m=%p p=%p *pos=%lld\n",
    + m, p, (unsigned long long)*pos);
    +
    + if (p == SEQ_START_TOKEN)
    + pq = pending_iter_first(iter);
    + else
    + pq = pending_iter_next(iter);
    + ++*pos;
    + return pq;
    +}
    +
    +/*
    + * Seq_ops show method. Called several times within a read()
    + * call from userspace, with pending_lock held. Formats the
    + * current pending_query as a single human-readable line, with a
    + * special case for the header line.
    + */
    +static int pending_proc_show(struct seq_file *m, void *p)
    +{
    + struct pending_iter *iter = m->private;
    + struct pending_query *pq = p;
    + char *qstr;
    +
    + pr_debug("called m=%p p=%p\n", m, p);
    +
    + if (p == SEQ_START_TOKEN) {
    + seq_puts(m, "# file module func line flags\n");
    + return 0;
    + }
    +
    + seq_printf(m, "%s\n", qstr = show_pending_query(iter->elem));
    + kfree(qstr);
    + return 0;
    +}
    +
    +/*
    + * Seq_ops stop method. Called at the end of each read()
    + * call from userspace. Drops pending_lock.
    + */
    +static void pending_proc_stop(struct seq_file *m, void *p)
    +{
    + pr_debug("called m=%p p=%p\n", m, p);
    + mutex_unlock(&ddebug_lock);
    +}
    +
    +static const struct seq_operations pending_proc_seqops = {
    + .start = pending_proc_start,
    + .next = pending_proc_next,
    + .show = pending_proc_show,
    + .stop = pending_proc_stop
    +};
    +
    +/*
    + * File_ops->open method for <debugfs>/dynamic_debug/control. Does the seq_file
    + * setup dance, and also creates an iterator to walk the pending_querys.
    + * Note that we create a seq_file always, even for O_WRONLY files
    + * where it's not needed, as doing so simplifies the ->release method.
    + */
    +static int pending_proc_open(struct inode *inode, struct file *file)
    +{
    + struct pending_iter *iter;
    + int err;
    +
    + if (verbose)
    + pr_info("called\n");
    +
    + iter = kzalloc(sizeof(*iter), GFP_KERNEL);
    + if (iter == NULL)
    + return -ENOMEM;
    +
    + err = seq_open(file, &pending_proc_seqops);
    + if (err) {
    + kfree(iter);
    + return err;
    + }
    + ((struct seq_file *) file->private_data)->private = iter;
    + return 0;
    +}
    +
    +static const struct file_operations pending_proc_fops = {
    + .owner = THIS_MODULE,
    + .open = pending_proc_open,
    + .read = seq_read,
    + .llseek = seq_lseek,
    + .release = seq_release_private,
    +};
    +
    /* apply matching queries in pending-queries list. Called with lock held */
    static void apply_pending_queries(struct ddebug_table *dt)
    {
    @@ -1051,7 +1211,7 @@ static __initdata int ddebug_init_success;

    static int __init dynamic_debug_init_debugfs(void)
    {
    - struct dentry *dir, *file;
    + struct dentry *dir, *file, *file2;

    if (!ddebug_init_success)
    return -ENODEV;
    @@ -1065,6 +1225,13 @@ static int __init dynamic_debug_init_debugfs(void)
    debugfs_remove(dir);
    return -ENOMEM;
    }
    + file2 = debugfs_create_file("pending", 0444, dir, NULL,
    + &pending_proc_fops);
    + if (!file2) {
    + debugfs_remove(file);
    + debugfs_remove(dir);
    + return -ENOMEM;
    + }
    return 0;
    }

    --
    1.7.4.1


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