RE: [PATCH] phy: rcar-gen3-usb2: fix mutex_lock calling in interrupt

[Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>]

Hi,

> From: Kishon Vijay Abraham I
> Sent: Wednesday, June 29, 2016 11:04 PM
> 
> +Chanwoo
> 
> Hi,
> 
> On Monday 27 June 2016 12:06 PM, Yoshihiro Shimoda wrote:
> > This patch fixes an issue that the extcon_set_cable_state_() is possible
> > to cause "BUG: scheduling while atomic" because this driver calls
> > extcon_set_cable_state_() in the interrupt handler and mutex_lock()
> 
> Doesn't extcon_set_cable_state_() use spin_lock?

If my understanding is correct, this issue is caused by kobject_uevent_env() finally.
(I should have wrote so in the commit log though...)

The kobject_uevent_env() has a global mutex value "uevent_sock_mutex".
Since it can be used other software, if other software get the mutext first and
the phy-rcar-gen3-usb2 will call extcon_set_cable_state_() from interrupt handler,
the kobject_uevent_env() is possible to be in interrupt, and then this BUG() happened.

Best regards,
Yoshihiro Shimoda

> Thanks
> Kishon
> 
> > is possible to be called by like the following call trace.
> > So, this patch adds a workqueue function to resolve this issue.
> >
> > [    9.706504] BUG: scheduling while atomic: systemd-journal/25893/0x00010303
> > [    9.714569] Modules linked in:
> > [    9.717629] CPU: 0 PID: 25893 Comm: systemd-journal Not tainted 4.7.0-rc4+ #86
> > [    9.724844] Hardware name: Renesas Salvator-X board based on r8a7795 (DT)
> > [    9.731624] Call trace:
> > [    9.734077] [<ffff0000080889f0>] dump_backtrace+0x0/0x1a8
> > [    9.739470] [<ffff000008088bac>] show_stack+0x14/0x20
> > [    9.744520] [<ffff000008348ab4>] dump_stack+0x94/0xb8
> > [    9.749568] [<ffff0000080da18c>] __schedule_bug+0x44/0x58
> > [    9.754966] [<ffff0000087c6394>] __schedule+0x4e4/0x598
> > [    9.760185] [<ffff0000087c6484>] schedule+0x3c/0xa8
> > [    9.765057] [<ffff0000087c6928>] schedule_preempt_disabled+0x20/0x38
> > [    9.771408] [<ffff0000080f20dc>] mutex_optimistic_spin+0x18c/0x1d0
> > [    9.777583] [<ffff0000087c7ef0>] __mutex_lock_slowpath+0x38/0x140
> > [    9.783669] [<ffff0000087c803c>] mutex_lock+0x44/0x60
> > [    9.788717] [<ffff00000834ca48>] kobject_uevent_env+0x250/0x500
> > [    9.794634] [<ffff0000086ae8c0>] extcon_update_state+0x220/0x298
> > [    9.800634] [<ffff0000086ae9d8>] extcon_set_cable_state_+0x78/0x88
> > [    9.806812] [<ffff000008376004>] rcar_gen3_device_recognition+0x5c/0xe0
> > [    9.813420] [<ffff0000083761bc>] rcar_gen3_phy_usb2_irq+0x3c/0x48
> > [    9.819509] [<ffff0000080fae94>] handle_irq_event_percpu+0x94/0x140
> > [    9.825769] [<ffff0000080faf88>] handle_irq_event+0x48/0x78
> > [    9.831334] [<ffff0000080fe620>] handle_fasteoi_irq+0xb8/0x1b0
> > [    9.837162] [<ffff0000080fa3c4>] generic_handle_irq+0x24/0x38
> > [    9.842900] [<ffff0000080fa6fc>] __handle_domain_irq+0x5c/0xb8
> > [    9.848727] [<ffff000008081520>] gic_handle_irq+0x58/0xb0
> >
> > Reported-by: Simon Horman <horms@verge.net.au>
> > Fixes: 2b38543c8db1 ("phy: rcar-gen3-usb2: add extcon support")
> > Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
> > ---
> >  drivers/phy/phy-rcar-gen3-usb2.c | 26 ++++++++++++++++++++++----
> >  1 file changed, 22 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/phy/phy-rcar-gen3-usb2.c b/drivers/phy/phy-rcar-gen3-usb2.c
> > index 4be3f5d..31156c9 100644
> > --- a/drivers/phy/phy-rcar-gen3-usb2.c
> > +++ b/drivers/phy/phy-rcar-gen3-usb2.c
> > @@ -21,6 +21,7 @@
> >  #include <linux/phy/phy.h>
> >  #include <linux/platform_device.h>
> >  #include <linux/regulator/consumer.h>
> > +#include <linux/workqueue.h>
> >
> >  /******* USB2.0 Host registers (original offset is +0x200) *******/
> >  #define USB2_INT_ENABLE		0x000
> > @@ -81,9 +82,25 @@ struct rcar_gen3_chan {
> >  	struct extcon_dev *extcon;
> >  	struct phy *phy;
> >  	struct regulator *vbus;
> > +	struct work_struct work;
> > +	bool extcon_host;
> >  	bool has_otg;
> >  };
> >
> > +static void rcar_gen3_phy_usb2_work(struct work_struct *work)
> > +{
> > +	struct rcar_gen3_chan *ch = container_of(work, struct rcar_gen3_chan,
> > +						 work);
> > +
> > +	if (ch->extcon_host) {
> > +		extcon_set_cable_state_(ch->extcon, EXTCON_USB_HOST, true);
> > +		extcon_set_cable_state_(ch->extcon, EXTCON_USB, false);
> > +	} else {
> > +		extcon_set_cable_state_(ch->extcon, EXTCON_USB_HOST, false);
> > +		extcon_set_cable_state_(ch->extcon, EXTCON_USB, true);
> > +	}
> > +}
> > +
> >  static void rcar_gen3_set_host_mode(struct rcar_gen3_chan *ch, int host)
> >  {
> >  	void __iomem *usb2_base = ch->base;
> > @@ -130,8 +147,8 @@ static void rcar_gen3_init_for_host(struct rcar_gen3_chan *ch)
> >  	rcar_gen3_set_host_mode(ch, 1);
> >  	rcar_gen3_enable_vbus_ctrl(ch, 1);
> >
> > -	extcon_set_cable_state_(ch->extcon, EXTCON_USB_HOST, true);
> > -	extcon_set_cable_state_(ch->extcon, EXTCON_USB, false);
> > +	ch->extcon_host = true;
> > +	schedule_work(&ch->work);
> >  }
> >
> >  static void rcar_gen3_init_for_peri(struct rcar_gen3_chan *ch)
> > @@ -140,8 +157,8 @@ static void rcar_gen3_init_for_peri(struct rcar_gen3_chan *ch)
> >  	rcar_gen3_set_host_mode(ch, 0);
> >  	rcar_gen3_enable_vbus_ctrl(ch, 0);
> >
> > -	extcon_set_cable_state_(ch->extcon, EXTCON_USB_HOST, false);
> > -	extcon_set_cable_state_(ch->extcon, EXTCON_USB, true);
> > +	ch->extcon_host = false;
> > +	schedule_work(&ch->work);
> >  }
> >
> >  static bool rcar_gen3_check_id(struct rcar_gen3_chan *ch)
> > @@ -301,6 +318,7 @@ static int rcar_gen3_phy_usb2_probe(struct platform_device *pdev)
> >  	if (irq >= 0) {
> >  		int ret;
> >
> > +		INIT_WORK(&channel->work, rcar_gen3_phy_usb2_work);
> >  		irq = devm_request_irq(dev, irq, rcar_gen3_phy_usb2_irq,
> >  				       IRQF_SHARED, dev_name(dev), channel);
> >  		if (irq < 0)
> >