Re: musb RPM sleep-while-atomic in 4.9-rc1

[Johan Hovold <johan-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

On Thu, Oct 27, 2016 at 08:14:46AM -0700, Tony Lindgren wrote:
> * Tony Lindgren <tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org> [161026 07:32]:

> 8< -------------------------------
> From tony Mon Sep 17 00:00:00 2001
> From: Tony Lindgren <tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org>
> Date: Tue, 25 Oct 2016 08:42:00 -0700
> Subject: [PATCH] usb: musb: Fix sleeping function called from invalid
>  context for hdrc glue
> 
> Commit 65b3f50ed6fa ("usb: musb: Add PM runtime support for MUSB DSPS
> glue layer") wrongly added a call for pm_runtime_get_sync to otg_timer
> that runs in softirq context. That causes a "BUG: sleeping function called
> from invalid context" every time when polling the cable status:
> 
> [<c015ebb4>] (__might_sleep) from [<c0413d60>] (__pm_runtime_resume+0x9c/0xa0)
> [<c0413d60>] (__pm_runtime_resume) from [<c04d0bc4>] (otg_timer+0x3c/0x254)
> [<c04d0bc4>] (otg_timer) from [<c0191180>] (call_timer_fn+0xfc/0x41c)
> [<c0191180>] (call_timer_fn) from [<c01915c0>] (expire_timers+0x120/0x210)
> [<c01915c0>] (expire_timers) from [<c0191acc>] (run_timer_softirq+0xa4/0xdc)
> [<c0191acc>] (run_timer_softirq) from [<c010168c>] (__do_softirq+0x12c/0x594)
> 
> I did not notice that as I did not have CONFIG_DEBUG_ATOMIC_SLEEP enabled.
> 
> Let's fix the issue by adding dsps_check_status() and then register a
> callback with musb_runtime_resume() so it gets called only when musb core
> and it's parent devices are awake. Note that we don't want to do this from
> PM runtime resume in musb_dsps.c as musb core is not awake yet at that
> point as noted by Johan Hovold <johan-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>.

It seems some chunks are missing since this patch only runs the
deferred work at remove and not at runtime resume, effectively breaking
detection.

> Note that musb_gadget_queue() also suffers from a similar issue when
> connecting the cable and cannot use pm_runtime_get_sync().

You seem to have left that pm_runtime_get_sync() in there though.

> Fixes: 65b3f50ed6fa ("usb: musb: Add PM runtime support for MUSB DSPS
> glue layer")
> Reported-by: Johan Hovold <johan-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> Signed-off-by: Tony Lindgren <tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org>
> ---
>  drivers/usb/musb/musb_core.c   | 44 +++++++++++++++++++++++++++++++++++++++++-
>  drivers/usb/musb/musb_core.h   |  7 +++++++
>  drivers/usb/musb/musb_dsps.c   | 29 +++++++++++++++++++++-------
>  drivers/usb/musb/musb_gadget.c | 16 +++++++++++++--
>  4 files changed, 86 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/usb/musb/musb_core.c b/drivers/usb/musb/musb_core.c
> --- a/drivers/usb/musb/musb_core.c
> +++ b/drivers/usb/musb/musb_core.c
> @@ -122,7 +122,6 @@ MODULE_AUTHOR(DRIVER_AUTHOR);
>  MODULE_LICENSE("GPL");
>  MODULE_ALIAS("platform:" MUSB_DRIVER_NAME);
>  
> -
>  /*-------------------------------------------------------------------------*/
>  
>  static inline struct musb *dev_to_musb(struct device *dev)
> @@ -1896,6 +1895,46 @@ static void musb_pm_runtime_check_session(struct musb *musb)
>  	musb->session = s;
>  }
>  
> +struct musb_resume_work {
> +	void (*callback)(struct musb *musb, void *data);
> +	void *data;
> +	struct list_head node;
> +};
> +
> +void musb_queue_on_resume(struct musb *musb,
> +			  void (*callback)(struct musb *musb, void *data),
> +			  void *data)
> +{
> +	struct musb_resume_work *w;
> +	unsigned long flags;
> +
> +	w = devm_kzalloc(musb->controller, sizeof(*w), GFP_ATOMIC);
> +	if (!w)
> +		return;
> +
> +	w->callback = callback;
> +	w->data = data;
> +	spin_lock_irqsave(&musb->list_lock, flags);
> +	list_add_tail(&w->node, &musb->resume_work);
> +	spin_unlock_irqrestore(&musb->list_lock, flags);
> +}
> +EXPORT_SYMBOL_GPL(musb_queue_on_resume);
> +
> +static void musb_run_pending(struct musb *musb)
> +{
> +	struct musb_resume_work *w, *_w;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&musb->list_lock, flags);
> +	list_for_each_entry_safe(w, _w, &musb->resume_work, node) {
> +		if (w->callback)
> +			w->callback(musb, w->data);
> +		list_del(&w->node);
> +		devm_kfree(musb->controller, w);
> +	}
> +	spin_unlock_irqrestore(&musb->list_lock, flags);
> +}
> +
>  /* Only used to provide driver mode change events */
>  static void musb_irq_work(struct work_struct *data)
>  {
> @@ -1969,6 +2008,7 @@ static struct musb *allocate_instance(struct device *dev,
>  	INIT_LIST_HEAD(&musb->control);
>  	INIT_LIST_HEAD(&musb->in_bulk);
>  	INIT_LIST_HEAD(&musb->out_bulk);
> +	INIT_LIST_HEAD(&musb->resume_work);
>  
>  	musb->vbuserr_retry = VBUSERR_RETRY_COUNT;
>  	musb->a_wait_bcon = OTG_TIME_A_WAIT_BCON;
> @@ -2065,6 +2105,7 @@ musb_init_controller(struct device *dev, int nIrq, void __iomem *ctrl)
>  	}
>  
>  	spin_lock_init(&musb->lock);
> +	spin_lock_init(&musb->list_lock);
>  	musb->board_set_power = plat->set_power;
>  	musb->min_power = plat->min_power;
>  	musb->ops = plat->platform_ops;
> @@ -2374,6 +2415,7 @@ static int musb_remove(struct platform_device *pdev)
>  	 *  - Peripheral mode: peripheral is deactivated (or never-activated)
>  	 *  - OTG mode: both roles are deactivated (or never-activated)
>  	 */
> +	musb_run_pending(musb);
>  	musb_exit_debugfs(musb);
>  
>  	cancel_work_sync(&musb->irq_work);
> diff --git a/drivers/usb/musb/musb_core.h b/drivers/usb/musb/musb_core.h
> --- a/drivers/usb/musb/musb_core.h
> +++ b/drivers/usb/musb/musb_core.h
> @@ -303,6 +303,7 @@ struct musb_context_registers {
>  struct musb {
>  	/* device lock */
>  	spinlock_t		lock;
> +	spinlock_t		list_lock;	/* resume work list lock */
>  
>  	struct musb_io		io;
>  	const struct musb_platform_ops *ops;
> @@ -337,6 +338,7 @@ struct musb {
>  	struct list_head	control;	/* of musb_qh */
>  	struct list_head	in_bulk;	/* of musb_qh */
>  	struct list_head	out_bulk;	/* of musb_qh */
> +	struct list_head	resume_work;	/* pending work on resume */
>  
>  	struct timer_list	otg_timer;
>  	struct notifier_block	nb;
> @@ -540,6 +542,11 @@ extern irqreturn_t musb_interrupt(struct musb *);
>  
>  extern void musb_hnp_stop(struct musb *musb);
>  
> +extern void
> +musb_queue_on_resume(struct musb *musb,
> +		     void (*callback)(struct musb *musb, void *data),
> +		     void *data);
> +
>  static inline void musb_platform_set_vbus(struct musb *musb, int is_on)
>  {
>  	if (musb->ops->set_vbus)
> diff --git a/drivers/usb/musb/musb_dsps.c b/drivers/usb/musb/musb_dsps.c
> --- a/drivers/usb/musb/musb_dsps.c
> +++ b/drivers/usb/musb/musb_dsps.c
> @@ -188,9 +188,8 @@ static void dsps_musb_disable(struct musb *musb)
>  	musb_writeb(musb->mregs, MUSB_DEVCTL, 0);
>  }
>  
> -static void otg_timer(unsigned long _musb)
> +static void dsps_check_status(struct musb *musb)
>  {
> -	struct musb *musb = (void *)_musb;
>  	void __iomem *mregs = musb->mregs;
>  	struct device *dev = musb->controller;
>  	struct dsps_glue *glue = dev_get_drvdata(dev->parent);
> @@ -198,11 +197,6 @@ static void otg_timer(unsigned long _musb)
>  	u8 devctl;
>  	unsigned long flags;
>  	int skip_session = 0;
> -	int err;
> -
> -	err = pm_runtime_get_sync(dev);
> -	if (err < 0)
> -		dev_err(dev, "Poll could not pm_runtime_get: %i\n", err);
>  
>  	/*
>  	 * We poll because DSPS IP's won't expose several OTG-critical
> @@ -246,6 +240,27 @@ static void otg_timer(unsigned long _musb)
>  		break;
>  	}
>  	spin_unlock_irqrestore(&musb->lock, flags);
> +}
> +
> +static void dsps_check_status_resume_work(struct musb *musb, void *unused)
> +{
> +	dsps_check_status(musb);
> +}
> +
> +static void otg_timer(unsigned long _musb)
> +{
> +	struct musb *musb = (void *)_musb;
> +	struct device *dev = musb->controller;
> +	int err;
> +
> +	err = pm_runtime_get(dev);
> +	if (err < 0)
> +		dev_err(dev, "Poll could not pm_runtime_get: %i\n", err);
> +
> +	if (pm_runtime_active(dev))
> +		dsps_check_status(musb);
> +	else
> +		musb_queue_on_resume(musb, dsps_check_status_resume_work, NULL);
>  
>  	pm_runtime_mark_last_busy(dev);
>  	pm_runtime_put_autosuspend(dev);
> diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c
> --- a/drivers/usb/musb/musb_gadget.c
> +++ b/drivers/usb/musb/musb_gadget.c
> @@ -1222,6 +1222,13 @@ void musb_ep_restart(struct musb *musb, struct musb_request *req)
>  		rxstate(musb, req);
>  }
>  
> +void musb_ep_restart_resume_work(struct musb *musb, void *data)
> +{
> +	struct musb_request *req = data;
> +
> +	musb_ep_restart(musb, req);

This one is supposed to be called with musb->lock held (according to the
function header anyway).

> +}
> +
>  static int musb_gadget_queue(struct usb_ep *ep, struct usb_request *req,
>  			gfp_t gfp_flags)
>  {
> @@ -1271,8 +1278,13 @@ static int musb_gadget_queue(struct usb_ep *ep, struct usb_request *req,
>  	list_add_tail(&request->list, &musb_ep->req_list);
>  
>  	/* it this is the head of the queue, start i/o ... */
> -	if (!musb_ep->busy && &request->list == musb_ep->req_list.next)
> -		musb_ep_restart(musb, request);
> +	if (!musb_ep->busy && &request->list == musb_ep->req_list.next) {
> +		if (pm_runtime_active(musb->controller))
> +			musb_ep_restart(musb, request);
> +		else
> +			musb_queue_on_resume(musb, musb_ep_restart_resume_work,
> +					     request);
> +	}
>  
>  unlock:
>  	spin_unlock_irqrestore(&musb->lock, lockflags);

And then this looks like it could trigger an ABBA deadlock as musb->lock
is held while queue_on_resume() takes musb->list_lock, and
musb_run_pending() would take the same locks in the reverse order.

Johan
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