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Date: Sun, 12 May 2013 21:59:51 +0800
From: Ming Lei <ming.lei@...onical.com>
To: Takashi Iwai <tiwai@...e.de>
Cc: linux-kernel@...r.kernel.org,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 1/3] firmware: Avoid superfluous usermodehelper lock
On Thu, May 9, 2013 at 1:51 AM, Takashi Iwai <tiwai@...e.de> wrote:
>
> ---
> From: Takashi Iwai <tiwai@...e.de>
> Subject: [PATCH v2] firmware: Avoid deadlock of usermodehelper lock at shutdown
>
> When a system goes to reboot/shutdown, it tries to disable the
> usermode helper via usermodehelper_disable(). This might be blocked
> when a driver tries to load a firmware beforehand and it's stuck by
> some reason.
>
> In this patch, the firmware class driver registers a reboot notifier
> so that it can abort all pending f/w bufs. Also enable a flag for
> avoiding the call of usermodehelper after the reboot/shutdown starts.
>
> Signed-off-by: Takashi Iwai <tiwai@...e.de>
> ---
> drivers/base/firmware_class.c | 40 +++++++++++++++++++++++++++++++++-------
> 1 file changed, 33 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
> index 4b1f926..972e535 100644
> --- a/drivers/base/firmware_class.c
> +++ b/drivers/base/firmware_class.c
> @@ -27,6 +27,7 @@
> #include <linux/pm.h>
> #include <linux/suspend.h>
> #include <linux/syscore_ops.h>
> +#include <linux/reboot.h>
>
> #include <generated/utsrelease.h>
>
> @@ -171,6 +172,7 @@ static struct firmware_buf *__allocate_fw_buf(const char *fw_name,
> strcpy(buf->fw_id, fw_name);
> buf->fwc = fwc;
> init_completion(&buf->completion);
> + INIT_LIST_HEAD(&buf->list);
You should introduce one extra field(such as, 'list_abort') in
'struct firmware_buf' and the field of 'list' is for firmware caching now.
Also, INIT_LIST_HEAD isn't needed here.
>
> pr_debug("%s: fw-%s buf=%p\n", __func__, fw_name, buf);
>
> @@ -446,10 +448,9 @@ static struct firmware_priv *to_firmware_priv(struct device *dev)
> return container_of(dev, struct firmware_priv, dev);
> }
>
> -static void fw_load_abort(struct firmware_priv *fw_priv)
> +static void fw_load_abort(struct firmware_buf *buf)
> {
> - struct firmware_buf *buf = fw_priv->buf;
> -
> + list_del_init(&buf->list);
> set_bit(FW_STATUS_ABORT, &buf->status);
> complete_all(&buf->completion);
> }
> @@ -457,6 +458,24 @@ static void fw_load_abort(struct firmware_priv *fw_priv)
> #define is_fw_load_aborted(buf) \
> test_bit(FW_STATUS_ABORT, &(buf)->status)
>
> +static LIST_HEAD(pending_fw_head);
> +
> +/* reboot notifier for avoid deadlock with usermode_lock */
> +static int fw_shutdown_notify(struct notifier_block *unused1,
> + unsigned long unused2, void *unused3)
> +{
> + mutex_lock(&fw_lock);
> + while (!list_empty(&pending_fw_head))
> + fw_load_abort(list_first_entry(&pending_fw_head,
> + struct firmware_buf, list));
> + mutex_unlock(&fw_lock);
> + return NOTIFY_DONE;
> +}
> +
> +static struct notifier_block fw_shutdown_nb = {
> + .notifier_call = fw_shutdown_notify,
> +};
> +
> static ssize_t firmware_timeout_show(struct class *class,
> struct class_attribute *attr,
> char *buf)
> @@ -604,6 +623,7 @@ static ssize_t firmware_loading_store(struct device *dev,
> * is completed.
> * */
> fw_map_pages_buf(fw_buf);
> + list_del_init(&fw_buf->list);
> complete_all(&fw_buf->completion);
> break;
> }
> @@ -612,7 +632,7 @@ static ssize_t firmware_loading_store(struct device *dev,
> dev_err(dev, "%s: unexpected value (%d)\n", __func__, loading);
> /* fallthrough */
> case -1:
> - fw_load_abort(fw_priv);
> + fw_load_abort(fw_buf);
> break;
> }
> out:
> @@ -680,7 +700,7 @@ static int fw_realloc_buffer(struct firmware_priv *fw_priv, int min_size)
> new_pages = kmalloc(new_array_size * sizeof(void *),
> GFP_KERNEL);
> if (!new_pages) {
> - fw_load_abort(fw_priv);
> + fw_load_abort(buf);
> return -ENOMEM;
> }
> memcpy(new_pages, buf->pages,
> @@ -697,7 +717,7 @@ static int fw_realloc_buffer(struct firmware_priv *fw_priv, int min_size)
> alloc_page(GFP_KERNEL | __GFP_HIGHMEM);
>
> if (!buf->pages[buf->nr_pages]) {
> - fw_load_abort(fw_priv);
> + fw_load_abort(buf);
> return -ENOMEM;
> }
> buf->nr_pages++;
> @@ -781,7 +801,7 @@ static void firmware_class_timeout_work(struct work_struct *work)
> mutex_unlock(&fw_lock);
> return;
> }
> - fw_load_abort(fw_priv);
> + fw_load_abort(fw_priv->buf);
> mutex_unlock(&fw_lock);
> }
>
> @@ -857,6 +877,10 @@ static int _request_firmware_load(struct firmware_priv *fw_priv, bool uevent,
> kobject_uevent(&fw_priv->dev.kobj, KOBJ_ADD);
> }
>
> + mutex_lock(&fw_lock);
> + list_add(&buf->list, &pending_fw_head);
> + mutex_unlock(&fw_lock);
> +
> wait_for_completion(&buf->completion);
>
> cancel_delayed_work_sync(&fw_priv->timeout_work);
> @@ -1517,6 +1541,7 @@ static int __init firmware_class_init(void)
> {
> fw_cache_init();
> #ifdef CONFIG_FW_LOADER_USER_HELPER
> + register_reboot_notifier(&fw_shutdown_nb);
> return class_register(&firmware_class);
> #else
> return 0;
> @@ -1530,6 +1555,7 @@ static void __exit firmware_class_exit(void)
> unregister_pm_notifier(&fw_cache.pm_notify);
> #endif
> #ifdef CONFIG_FW_LOADER_USER_HELPER
> + unregister_reboot_notifier(&fw_shutdown_nb);
> class_unregister(&firmware_class);
> #endif
> }
> --
> 1.8.2.1
Thanks,
--
Ming Lei
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