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SubjectRe: [PATCH V2] firmware loader: Fix the race FW_STATUS_DONE is followed by class_timeout
From
On Thu, Nov 8, 2012 at 6:29 PM, Chuansheng Liu <chuansheng.liu@intel.com> wrote:
>
> There is a race as below when calling request_firmware():
> CPU1 CPU2
> write 0 > loading
> mutex_lock(&fw_lock)
> ...
> set_bit FW_STATUS_DONE class_timeout is coming
> set_bit FW_STATUS_ABORT
> complete_all &completion
> ...
> mutex_unlock(&fw_lock)
>
> In this time, the bit FW_STATUS_DONE and FW_STATUS_ABORT are set,
> and request_firmware() will return failure due to condition in
> _request_firmware_load():
> if (!buf->size || test_bit(FW_STATUS_ABORT, &buf->status))
> retval = -ENOENT;
>
> But from the above scenerio, it should be a successful requesting.
> So we need judge if the bit FW_STATUS_DONE is already set before
> calling fw_load_abort() in timeout function.
>
> As Ming's proposal, we need change the timer into sched_work to
> benefit from using &fw_lock mutex also.
>
> Signed-off-by: liu chuansheng <chuansheng.liu@intel.com>
> ---
> drivers/base/firmware_class.c | 25 +++++++++++++++++--------
> 1 files changed, 17 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
> index 8945f4e..f2caa0a 100644
> --- a/drivers/base/firmware_class.c
> +++ b/drivers/base/firmware_class.c
> @@ -143,7 +143,7 @@ struct fw_cache_entry {
> };
>
> struct firmware_priv {
> - struct timer_list timeout;
> + struct delayed_work timeout_work;
> bool nowait;
> struct device dev;
> struct firmware_buf *buf;
> @@ -667,10 +667,17 @@ static struct bin_attribute firmware_attr_data = {
> .write = firmware_data_write,
> };
>
> -static void firmware_class_timeout(u_long data)
> +static void firmware_class_timeout_work(struct work_struct *work)
> {
> - struct firmware_priv *fw_priv = (struct firmware_priv *) data;
> + struct firmware_priv *fw_priv = container_of(work,
> + struct firmware_priv, timeout_work.work);
>
> + mutex_lock(&fw_lock);
> + if (test_bit(FW_STATUS_DONE, &(fw_priv->buf->status))) {
> + mutex_unlock(&fw_lock);
> + return;
> + }
> + mutex_unlock(&fw_lock);
> fw_load_abort(fw_priv);

fw_lock should be held when fw_load_abort(fw_priv) is running.

> }
>
> @@ -690,8 +697,8 @@ fw_create_instance(struct firmware *firmware, const char *fw_name,
>
> fw_priv->nowait = nowait;
> fw_priv->fw = firmware;
> - setup_timer(&fw_priv->timeout,
> - firmware_class_timeout, (u_long) fw_priv);
> + INIT_DELAYED_WORK(&fw_priv->timeout_work,
> + firmware_class_timeout_work);
>
> f_dev = &fw_priv->dev;
>
> @@ -858,7 +865,9 @@ static int _request_firmware_load(struct firmware_priv *fw_priv, bool uevent,
> dev_dbg(f_dev->parent, "firmware: direct-loading"
> " firmware %s\n", buf->fw_id);
>
> + mutex_lock(&fw_lock);
> set_bit(FW_STATUS_DONE, &buf->status);
> + mutex_unlock(&fw_lock);
> complete_all(&buf->completion);
> direct_load = 1;
> goto handle_fw;
> @@ -894,15 +903,15 @@ static int _request_firmware_load(struct firmware_priv *fw_priv, bool uevent,
> dev_set_uevent_suppress(f_dev, false);
> dev_dbg(f_dev, "firmware: requesting %s\n", buf->fw_id);
> if (timeout != MAX_SCHEDULE_TIMEOUT)
> - mod_timer(&fw_priv->timeout,
> - round_jiffies_up(jiffies + timeout));
> + schedule_delayed_work(&fw_priv->timeout_work,
> + timeout * HZ);

timeout is in unit of jiffies already, so multiplying by 'HZ' isn't needed.

>
> kobject_uevent(&fw_priv->dev.kobj, KOBJ_ADD);
> }
>
> wait_for_completion(&buf->completion);
>
> - del_timer_sync(&fw_priv->timeout);
> + cancel_delayed_work_sync(&fw_priv->timeout_work);
>
> handle_fw:
> mutex_lock(&fw_lock);
> --
> 1.7.0.4
>
>
>

Thanks,
--
Ming Lei


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