linux-kernel - Re: [PATCH v4] usb: xhci: tegra: fix sleep in atomic call

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Message-ID: <3f864eb32214399b911a62c2223abd250f41e1fa.camel@nvidia.com>
Date:   Fri, 24 Mar 2023 06:46:04 +0000
From:   Haotien Hsu <haotienh@...dia.com>
To:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
CC:     "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "thierry.reding@...il.com" <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Haotien Hsu <haotienh@...dia.com>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        Wayne Chang <waynec@...dia.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "mathias.nyman@...el.com" <mathias.nyman@...el.com>,
        "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
        Jui Chang Kuo <jckuo@...dia.com>
Subject: Re: [PATCH v4] usb: xhci: tegra: fix sleep in atomic call

On Thu, 2023-03-23 at 17:22 +0100, Greg Kroah-Hartman wrote:
> External email: Use caution opening links or attachments
> 
> 
> On Tue, Mar 21, 2023 at 03:29:46PM +0800, Haotien Hsu wrote:
> > From: Wayne Chang <waynec@...dia.com>
> > 
> > When we set the OTG port to Host mode, we observed the following
> > splat:
> 
> What "OTG" port?  That is not a USB thing anymore at all.  How is
> this
> part of a xhci controller?

I will use 'dual-role port' instead.

When the role of a super-speed port is switched, we need to clear or
set port power.
Our host mode controller and device mode controller share the same
super-speed port hardware.
When a SS port is going to be switched to device mode role, we have to
clear PP at host mode controller side to release SS port hardware to
device mode controller.
When a SS port is going to be switched to host mode role, we have to
set PP at host mode controller side to acquire SS port hardware.

> 
> > [  167.057718] BUG: sleeping function called from invalid context
> > at
> > include/linux/sched/mm.h:229
> > [  167.057872] Workqueue: events tegra_xusb_usb_phy_work
> > [  167.057954] Call trace:
> > [  167.057962]  dump_backtrace+0x0/0x210
> > [  167.057996]  show_stack+0x30/0x50
> > [  167.058020]  dump_stack_lvl+0x64/0x84
> > [  167.058065]  dump_stack+0x14/0x34
> > [  167.058100]  __might_resched+0x144/0x180
> > [  167.058140]  __might_sleep+0x64/0xd0
> > [  167.058171]  slab_pre_alloc_hook.constprop.0+0xa8/0x110
> > [  167.058202]  __kmalloc_track_caller+0x74/0x2b0
> > [  167.058233]  kvasprintf+0xa4/0x190
> > [  167.058261]  kasprintf+0x58/0x90
> > [  167.058285]  tegra_xusb_find_port_node.isra.0+0x58/0xd0
> > [  167.058334]  tegra_xusb_find_port+0x38/0xa0
> > [  167.058380]  tegra_xusb_padctl_get_usb3_companion+0x38/0xd0
> > [  167.058430]  tegra_xhci_id_notify+0x8c/0x1e0
> > [  167.058473]  notifier_call_chain+0x88/0x100
> > [  167.058506]  atomic_notifier_call_chain+0x44/0x70
> > [  167.058537]  tegra_xusb_usb_phy_work+0x60/0xd0
> > [  167.058581]  process_one_work+0x1dc/0x4c0
> > [  167.058618]  worker_thread+0x54/0x410
> > [  167.058650]  kthread+0x188/0x1b0
> > [  167.058672]  ret_from_fork+0x10/0x20
> > 
> > The function tegra_xusb_padctl_get_usb3_companion eventually calls
> > tegra_xusb_find_port and this in turn calls kasprintf which might
> > sleep
> > and so cannot be called from an atomic context.
> > 
> > Fix this by moving the call to tegra_xusb_padctl_get_usb3_companion
> > to
> > the tegra_xhci_id_work function where it is really needed.
> > 
> > Fixes: f836e7843036 ("usb: xhci-tegra: Add OTG support")
> > Cc: stable@...r.kernel.org
> > Signed-off-by: Wayne Chang <waynec@...dia.com>
> > Signed-off-by: Haotien Hsu <haotienh@...dia.com>
> > ---
> > V3 -> V4: Remove copyright change from this patch
> > V2 -> V3: Add version information
> > V1 -> V2: Add "Fixes" and "Cc:" lines and update copyright years
> > ---
> >  drivers/usb/host/xhci-tegra.c | 7 ++++---
> >  1 file changed, 4 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/usb/host/xhci-tegra.c b/drivers/usb/host/xhci-
> > tegra.c
> > index 1ff22f675930..b40e897ec092 100644
> > --- a/drivers/usb/host/xhci-tegra.c
> > +++ b/drivers/usb/host/xhci-tegra.c
> > @@ -1360,6 +1360,10 @@ static void tegra_xhci_id_work(struct
> > work_struct *work)
> > 
> >       mutex_unlock(&tegra->lock);
> > 
> > +     tegra->otg_usb3_port = tegra_xusb_padctl_get_usb3_companion(
> > +                                                     tegra-
> > >padctl,
> > +                                                     tegra-
> > >otg_usb2_port);
> > +
> 
> You have 100 columns, please use them, ending a line with "(" is not
> generally a good idea.

I will resubmit a new patch.

> 
> thanks,
> 
> greg k-h