linux-kernel - Re: [PATCH v11 26/33] counter: Add character device interface

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Message-ID: <20210609080708.GL10983@kadam>
Date:   Wed, 9 Jun 2021 11:07:08 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     William Breathitt Gray <vilhelm.gray@...il.com>
Cc:     jic23@...nel.org, linux-stm32@...md-mailman.stormreply.com,
        kernel@...gutronix.de, a.fatoum@...gutronix.de,
        kamel.bouhara@...tlin.com, gwendal@...omium.org,
        alexandre.belloni@...tlin.com, david@...hnology.com,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, syednwaris@...il.com,
        patrick.havelange@...ensium.com, fabrice.gasnier@...com,
        mcoquelin.stm32@...il.com, alexandre.torgue@...com,
        o.rempel@...gutronix.de, jarkko.nikula@...ux.intel.com
Subject: Re: [PATCH v11 26/33] counter: Add character device interface

On Wed, Jun 09, 2021 at 10:31:29AM +0900, William Breathitt Gray wrote:
> +static int counter_set_event_node(struct counter_device *const counter,
> +				  struct counter_watch *const watch,
> +				  const struct counter_comp_node *const cfg)
> +{
> +	struct counter_event_node *event_node;
> +	struct counter_comp_node *comp_node;
> +

The caller should be holding the counter->events_list_lock lock but it's
not.


> +	/* Search for event in the list */
> +	list_for_each_entry(event_node, &counter->next_events_list, l)
> +		if (event_node->event == watch->event &&
> +		    event_node->channel == watch->channel)
> +			break;
> +
> +	/* If event is not already in the list */
> +	if (&event_node->l == &counter->next_events_list) {
> +		/* Allocate new event node */
> +		event_node = kmalloc(sizeof(*event_node), GFP_ATOMIC);
> +		if (!event_node)
> +			return -ENOMEM;
> +
> +		/* Configure event node and add to the list */
> +		event_node->event = watch->event;
> +		event_node->channel = watch->channel;
> +		INIT_LIST_HEAD(&event_node->comp_list);
> +		list_add(&event_node->l, &counter->next_events_list);
> +	}
> +
> +	/* Check if component watch has already been set before */
> +	list_for_each_entry(comp_node, &event_node->comp_list, l)
> +		if (comp_node->parent == cfg->parent &&
> +		    comp_node->comp.count_u8_read == cfg->comp.count_u8_read)
> +			return -EINVAL;
> +
> +	/* Allocate component node */
> +	comp_node = kmalloc(sizeof(*comp_node), GFP_ATOMIC);
> +	if (!comp_node) {
> +		/* Free event node if no one else is watching */
> +		if (list_empty(&event_node->comp_list)) {
> +			list_del(&event_node->l);
> +			kfree(event_node);
> +		}
> +		return -ENOMEM;
> +	}
> +	*comp_node = *cfg;
> +
> +	/* Add component node to event node */
> +	list_add_tail(&comp_node->l, &event_node->comp_list);
> +
> +	return 0;
> +}
> +
> +static int counter_disable_events(struct counter_device *const counter)
> +{
> +	unsigned long flags;
> +	int err = 0;
> +
> +	spin_lock_irqsave(&counter->events_list_lock, flags);
> +
> +	counter_events_list_free(&counter->events_list);
> +
> +	if (counter->ops->events_configure)
> +		err = counter->ops->events_configure(counter);
> +
> +	spin_unlock_irqrestore(&counter->events_list_lock, flags);
> +
> +	counter_events_list_free(&counter->next_events_list);
> +
> +	return err;
> +}
> +
> +static int counter_add_watch(struct counter_device *const counter,
> +			     const unsigned long arg)
> +{
> +	void __user *const uwatch = (void __user *)arg;
> +	struct counter_watch watch;
> +	struct counter_comp_node comp_node = {0};

Always use = {};.  It's the new hotness, and it avoids a Sparse warning
for using 0 instead of NULL.  #IDidNotTest #CouldBeWrongAboutSparse

> +	size_t parent, id;
> +	struct counter_comp *ext;
> +	size_t num_ext;
> +	int err;
> +

regards,
dan carpenter