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Date: Wed, 17 May 2023 05:04:19 -0700
From: Badhri Jagan Sridharan <badhri@...gle.com>
To: gregkh@...uxfoundation.org, stern@...land.harvard.edu,
colin.i.king@...il.com, xuetao09@...wei.com,
quic_eserrao@...cinc.com, water.zhangjiantao@...wei.com,
peter.chen@...escale.com, balbi@...com, francesco@...cini.it,
alistair@...stair23.me, stephan@...hold.net, bagasdotme@...il.com,
luca@...tu.xyz
Cc: linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
stable@...r.kernel.org,
Francesco Dolcini <francesco.dolcini@...adex.com>
Subject: Re: [PATCH v1] usb: gadget: udc: core: Offload usb_udc_vbus_handler processing
Hi Francesco, Alistair, Stephan, Bagas, Lucas,
Thanks for sharing the stack traces !
Requesting your help on validating the patch as I dont have the same
hardware with me which reproduces the issue.
Let me know if you are still seeing the crash.
Thanks,
Badhri
On Wed, May 17, 2023 at 5:00 AM Badhri Jagan Sridharan
<badhri@...gle.com> wrote:
>
> chipidea udc calls usb_udc_vbus_handler from udc_start gadget
> ops causing a deadlock. Avoid this by offloading usb_udc_vbus_handler
> processing.
>
> ============================================
> WARNING: possible recursive locking detected
> 640-rc1-000-devel-00005-gcda3c69ebc14 #1 Not tainted
> -------------------------------------------
>
> CPU0
> ----
> lock(&udc->connect_lock);
> lock(&udc->connect_lock);
>
> DEADLOCK
>
> stack backtrace:
> CPU: 1 PID: 566 Comm: echo Not tainted 640-rc1-000-devel-00005-gcda3c69ebc14 #1
> Hardware name: Freescale iMX7 Dual (Device Tree)
> unwind_backtrace from show_stack+0x10/0x14
> show_stack from dump_stack_lvl+0x70/0xb0
> dump_stack_lvl from __lock_acquire+0x924/0x22c4
> __lock_acquire from lock_acquire+0x100/0x370
> lock_acquire from __mutex_lock+0xa8/0xfb4
> __mutex_lock from mutex_lock_nested+0x1c/0x24
> mutex_lock_nested from usb_udc_vbus_handler+0x1c/0x60
> usb_udc_vbus_handler from ci_udc_start+0x74/0x9c
> ci_udc_start from gadget_bind_driver+0x130/0x230
> gadget_bind_driver from really_probe+0xd8/0x3fc
> really_probe from __driver_probe_device+0x94/0x1f0
> __driver_probe_device from driver_probe_device+0x2c/0xc4
> driver_probe_device from __driver_attach+0x114/0x1cc
> __driver_attach from bus_for_each_dev+0x7c/0xcc
> bus_for_each_dev from bus_add_driver+0xd4/0x200
> bus_add_driver from driver_register+0x7c/0x114
> driver_register from usb_gadget_register_driver_owner+0x40/0xe0
> usb_gadget_register_driver_owner from gadget_dev_desc_UDC_store+0xd4/0x110
> gadget_dev_desc_UDC_store from configfs_write_iter+0xac/0x118
> configfs_write_iter from vfs_write+0x1b4/0x40c
> vfs_write from ksys_write+0x70/0xf8
> ksys_write from ret_fast_syscall+0x0/0x1c
>
> Fixes: 0db213ea8eed ("usb: gadget: udc: core: Invoke usb_gadget_connect only when started")
> Cc: stable@...r.kernel.org
> Reported-by: Stephan Gerhold <stephan@...hold.net>
> Closes: https://lore.kernel.org/all/ZF4bMptC3Lf2Hnee@gerhold.net/
> Reported-by: Francesco Dolcini <francesco.dolcini@...adex.com>
> Closes: https://lore.kernel.org/all/ZF4BvgsOyoKxdPFF@francesco-nb.int.toradex.com/
> Reported-by: Alistair <alistair@...stair23.me>
> Closes: https://lore.kernel.org/lkml/0cf8c588b701d7cf25ffe1a9217b81716e6a5c51.camel@alistair23.me/
> Signed-off-by: Badhri Jagan Sridharan <badhri@...gle.com>
> ---
> drivers/usb/gadget/udc/core.c | 55 +++++++++++++++++++++++++++++++----
> 1 file changed, 49 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
> index 69041cca5d24..bbcfab50f657 100644
> --- a/drivers/usb/gadget/udc/core.c
> +++ b/drivers/usb/gadget/udc/core.c
> @@ -41,6 +41,9 @@ static const struct bus_type gadget_bus_type;
> * functions. usb_gadget_connect_locked, usb_gadget_disconnect_locked,
> * usb_udc_connect_control_locked, usb_gadget_udc_start_locked, usb_gadget_udc_stop_locked are
> * called with this lock held.
> + * @vbus_events: list head for processing vbus updates on usb_udc_vbus_handler.
> + * @vbus_events_lock: protects vbus_events list
> + * @vbus_work: work item that invokes usb_udc_connect_control_locked.
> *
> * This represents the internal data structure which is used by the UDC-class
> * to hold information about udc driver and gadget together.
> @@ -53,6 +56,19 @@ struct usb_udc {
> bool vbus;
> bool started;
> struct mutex connect_lock;
> + struct list_head vbus_events;
> + struct mutex vbus_events_lock;
> + struct work_struct vbus_work;
> +};
> +
> +/**
> + * struct vbus_event - used to notify vbus updates posted through usb_udc_vbus_handler.
> + * @vbus_on: true when vbus is on. false other wise.
> + * @node: list node for maintaining a list of pending updates to be processed.
> + */
> +struct vbus_event {
> + bool vbus_on;
> + struct list_head node;
> };
>
> static struct class *udc_class;
> @@ -1134,6 +1150,23 @@ static int usb_udc_connect_control_locked(struct usb_udc *udc) __must_hold(&udc-
> return ret;
> }
>
> +static void vbus_event_work(struct work_struct *work)
> +{
> + struct vbus_event *event, *n;
> + struct usb_udc *udc = container_of(work, struct usb_udc, vbus_work);
> +
> + mutex_lock(&udc->vbus_events_lock);
> + list_for_each_entry_safe(event, n, &udc->vbus_events, node) {
> + mutex_lock(&udc->connect_lock);
> + udc->vbus = event->vbus_on;
> + usb_udc_connect_control_locked(udc);
> + list_del(&event->node);
> + kfree(event);
> + mutex_unlock(&udc->connect_lock);
> + }
> + mutex_unlock(&udc->vbus_events_lock);
> +}
> +
> /**
> * usb_udc_vbus_handler - updates the udc core vbus status, and try to
> * connect or disconnect gadget
> @@ -1146,13 +1179,20 @@ static int usb_udc_connect_control_locked(struct usb_udc *udc) __must_hold(&udc-
> void usb_udc_vbus_handler(struct usb_gadget *gadget, bool status)
> {
> struct usb_udc *udc = gadget->udc;
> + struct vbus_event *vbus_event;
>
> - mutex_lock(&udc->connect_lock);
> - if (udc) {
> - udc->vbus = status;
> - usb_udc_connect_control_locked(udc);
> - }
> - mutex_unlock(&udc->connect_lock);
> + if (!udc)
> + return;
> +
> + vbus_event = kzalloc(sizeof(*vbus_event), GFP_KERNEL);
> + if (!vbus_event)
> + return;
> +
> + mutex_lock(&udc->vbus_events_lock);
> + vbus_event->vbus_on = status;
> + list_add_tail(&vbus_event->node, &udc->vbus_events);
> + mutex_unlock(&udc->vbus_events_lock);
> + schedule_work(&udc->vbus_work);
> }
> EXPORT_SYMBOL_GPL(usb_udc_vbus_handler);
>
> @@ -1379,6 +1419,9 @@ int usb_add_gadget(struct usb_gadget *gadget)
> udc->gadget = gadget;
> gadget->udc = udc;
> mutex_init(&udc->connect_lock);
> + INIT_LIST_HEAD(&udc->vbus_events);
> + mutex_init(&udc->vbus_events_lock);
> + INIT_WORK(&udc->vbus_work, vbus_event_work);
>
> udc->started = false;
>
>
> base-commit: 6bae03b0484b54f699d69339fbec5658e885c224
> --
> 2.40.1.606.ga4b1b128d6-goog
>
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