From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Airlie Date: Wed, 01 Aug 2018 22:31:41 +0000 Subject: Re: Sleeping from invalid context in udlfb Message-Id: MIME-Version: 1 Content-Type: multipart/mixed; boundary="0000000000003ee66f05726742e5" List-Id: References: <6008699.T6Yd1fn3Dk@amdc3058> <1975707.vO8kdHz3oS@amdc3058> In-Reply-To: To: Mikulas Patocka Cc: Linux Fbdev development list , Ladislav Michl , Bartlomiej Zolnierkiewicz , Greg KH , Bernie Thompson , DRI Development , Linux Kernel Mailing List , Geert Uytterhoeven , Jiri Slaby --0000000000003ee66f05726742e5 Content-Type: text/plain; charset="UTF-8" I'm pretty sure udlkms handles this already. Dave. On Wed, Aug 1, 2018 at 11:34 PM, Mikulas Patocka wrote: > > > On Wed, 1 Aug 2018, Geert Uytterhoeven wrote: > > > Hi Mikulas, > > > > On Wed, Aug 1, 2018 at 12:59 PM Mikulas Patocka > wrote: > > > On Wed, 1 Aug 2018, Geert Uytterhoeven wrote: > > > > On Tue, Jul 31, 2018 at 5:23 PM Mikulas Patocka > wrote: > > > > > BTW when using the udlfb driver as a console, I've got this > warning. > > > > > vt_console_print takes a spinlock and then calls the framebuffer > driver > > > > > that sleeps. > > > > > > > > > > The question is - whose fault is this? Could the console code > somehow be > > > > > told to print characters without holding a spinlock? Or does it > mean that > > > > > framebuffer drivers can't sleep? > > > > > > > > > > udlfb communicates through USB, so the sleeping is inevitable. > > > > > > > > > > Mikulas > > > > > > > > > > > > > > > BUG: sleeping function called from invalid context at mm/slab.h:421 > > > > > in_atomic(): 1, irqs_disabled(): 0, pid: 430, name: kworker/2:3 > > > > > 6 locks held by kworker/2:3/430: > > > > > #0: 000000001301127e ( (wq_completion)"events"){....} , at: > process_one_work+0x17c/0x3a8 > > > > > #1: 00000000beacc951 ( (work_completion)(&(&dlfb-> > init_framebuffer_work)->work)){....} , at: process_one_work+0x17c/0x3a8 > > > > > #2: 00000000a402f826 ( registration_lock){....} , at: > register_framebuffer+0x28/0x2c0 [fb] > > > > > #3: 0000000021cbe902 ( console_lock){....} , at: > register_framebuffer+0x258/0x2c0 [fb] > > > > > #4: 0000000096d51735 ( console_owner){....} , at: > console_unlock+0x174/0x500 > > > > > #5: 00000000faa7f206 ( printing_lock){....} , at: > vt_console_print+0x60/0x3a0 > > > > > Preemption disabled at: [] > vt_console_print+0x60/0x3a0 > > > > > CPU: 2 PID: 430 Comm: kworker/2:3 Not tainted 4.17.10-debug #3 > > > > > Hardware name: Marvell Armada 8040 MacchiatoBin/Armada 8040 > MacchiatoBin, BIOS EDK II Jul 30 2018 > > > > > Workqueue: events dlfb_init_framebuffer_work [udlfb] > > > > > Call trace: > > > > > dump_backtrace+0x0/0x150 > > > > > show_stack+0x14/0x20 > > > > > dump_stack+0x8c/0xac > > > > > ___might_sleep+0x140/0x170 > > > > > __might_sleep+0x50/0x88 > > > > > __kmalloc+0x1b0/0x270 > > > > > xhci_urb_enqueue+0xa8/0x460 [xhci_hcd] > > > > > usb_hcd_submit_urb+0xc0/0x998 [usbcore] > > > > > usb_submit_urb+0x1e0/0x518 [usbcore] > > > > > dlfb_submit_urb+0x38/0x98 [udlfb] > > > > > dlfb_handle_damage.isra.4+0x1e0/0x210 [udlfb] > > > > > dlfb_ops_imageblit+0x28/0x38 [udlfb] > > > > > soft_cursor+0x15c/0x1d8 [fb] > > > > > bit_cursor+0x324/0x510 [fb] > > > > > fbcon_cursor+0x144/0x1a0 [fb] > > > > > hide_cursor+0x38/0xa0 > > > > > vt_console_print+0x334/0x3a0 > > > > > console_unlock+0x274/0x500 > > > > > register_framebuffer+0x22c/0x2c0 [fb] > > > > > dlfb_init_framebuffer_work+0x1ec/0x2fc [udlfb] > > > > > process_one_work+0x1e8/0x3a8 > > > > > worker_thread+0x44/0x418 > > > > > kthread+0x11c/0x120 > > > > > ret_from_fork+0x10/0x18 > > > > > > > > This is sort of expected: you cannot do USB transfers from printk(). > > > > > > > > Gr{oetje,eeting}s, > > > > > > > > Geert > > > > > > So, should there be a framebuffer flag that prevents the console from > > > binding to it? > > > > > > If I start the kernel with "console=ttyS0,115200", it doesn't try to > bind > > > to the udlfb driver, but if I start it without this flag, it does and > > > crashes :-( > > > > Your frame buffer driver should offload tasks that may sleep to e.g. a > > workqueue. > > > > Gr{oetje,eeting}s, > > > > Geert > > I can try to do this - but - taking a spinlock and copying 8MB framebuffer > would damage scheduling latency even for PCI framebuffer drivers. > > Mikulas > --0000000000003ee66f05726742e5 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable

I'm pretty sure udlkms handles thi= s already.

Dave.

On Wed, Aug 1, 2018 at 11:34 PM, Mi= kulas Patocka <mpatocka@redhat.com> wrote:


On Wed, 1 Aug 2018, Geert Uytterhoeven wrote:

> Hi Mikulas,
>
> On Wed, Aug 1, 2018 at 12:59 PM Mikulas Patocka <mpatocka@redhat.com> wrote:
> > On Wed, 1 Aug 2018, Geert Uytterhoeven wrote:
> > > On Tue, Jul 31, 2018 at 5:23 PM Mikulas Patocka <mpatocka@redhat.com> wrote:
> > > > BTW when using the udlfb driver as a console, I've = got this warning.
> > > > vt_console_print takes a spinlock and then calls the fr= amebuffer driver
> > > > that sleeps.
> > > >
> > > > The question is - whose fault is this? Could the consol= e code somehow be
> > > > told to print characters without holding a spinlock? Or= does it mean that
> > > > framebuffer drivers can't sleep?
> > > >
> > > > udlfb communicates through USB, so the sleeping is inev= itable.
> > > >
> > > > Mikulas
> > > >
> > > >
> > > > BUG: sleeping function called from invalid context at m= m/slab.h:421
> > > > in_atomic(): 1, irqs_disabled(): 0, pid: 430, name: kwo= rker/2:3
> > > > 6 locks held by kworker/2:3/430:
> > > >=C2=A0 #0: 000000001301127e ( (wq_completion)"event= s"){....} , at: process_one_work+0x17c/0x3a8
> > > >=C2=A0 #1: 00000000beacc951 ( (work_completion)(&(&a= mp;dlfb->init_framebuffer_work)->work)){....} , at: process= _one_work+0x17c/0x3a8
> > > >=C2=A0 #2: 00000000a402f826 ( registration_lock){....} ,= at: register_framebuffer+0x28/0x2c0 [fb]
> > > >=C2=A0 #3: 0000000021cbe902 ( console_lock){....} , at: = register_framebuffer+0x258/0x2c0 [fb]
> > > >=C2=A0 #4: 0000000096d51735 ( console_owner){....} , at:= console_unlock+0x174/0x500
> > > >=C2=A0 #5: 00000000faa7f206 ( printing_lock){....} , at:= vt_console_print+0x60/0x3a0
> > > > Preemption disabled at: [<ffffff8008403130>] vt_c= onsole_print+0x60/0x3a0
> > > > CPU: 2 PID: 430 Comm: kworker/2:3 Not tainted 4.17.10-d= ebug #3
> > > > Hardware name: Marvell Armada 8040 MacchiatoBin/Armada = 8040 MacchiatoBin, BIOS EDK II Jul 30 2018
> > > > Workqueue: events dlfb_init_framebuffer_work [udlfb] > > > > Call trace:
> > > >=C2=A0 dump_backtrace+0x0/0x150
> > > >=C2=A0 show_stack+0x14/0x20
> > > >=C2=A0 dump_stack+0x8c/0xac
> > > >=C2=A0 ___might_sleep+0x140/0x170
> > > >=C2=A0 __might_sleep+0x50/0x88
> > > >=C2=A0 __kmalloc+0x1b0/0x270
> > > >=C2=A0 xhci_urb_enqueue+0xa8/0x460 [xhci_hcd]
> > > >=C2=A0 usb_hcd_submit_urb+0xc0/0x998 [usbcore]
> > > >=C2=A0 usb_submit_urb+0x1e0/0x518 [usbcore]
> > > >=C2=A0 dlfb_submit_urb+0x38/0x98 [udlfb]
> > > >=C2=A0 dlfb_handle_damage.isra.4+0x1e0/0x210 [udlfb= ]
> > > >=C2=A0 dlfb_ops_imageblit+0x28/0x38 [udlfb]
> > > >=C2=A0 soft_cursor+0x15c/0x1d8 [fb]
> > > >=C2=A0 bit_cursor+0x324/0x510 [fb]
> > > >=C2=A0 fbcon_cursor+0x144/0x1a0 [fb]
> > > >=C2=A0 hide_cursor+0x38/0xa0
> > > >=C2=A0 vt_console_print+0x334/0x3a0
> > > >=C2=A0 console_unlock+0x274/0x500
> > > >=C2=A0 register_framebuffer+0x22c/0x2c0 [fb]
> > > >=C2=A0 dlfb_init_framebuffer_work+0x1ec/0x2fc [udlf= b]
> > > >=C2=A0 process_one_work+0x1e8/0x3a8
> > > >=C2=A0 worker_thread+0x44/0x418
> > > >=C2=A0 kthread+0x11c/0x120
> > > >=C2=A0 ret_from_fork+0x10/0x18
> > >
> > > This is sort of expected: you cannot do USB transfers from p= rintk().
> > >
> > > Gr{oetje,eeting}s,
> > >
> > >=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0Geert
> >
> > So, should there be a framebuffer flag that prevents the console = from
> > binding to it?
> >
> > If I start the kernel with "console=3DttyS0,115200", it= doesn't try to bind
> > to the udlfb driver, but if I start it without this flag, it does= and
> > crashes :-(
>
> Your frame buffer driver should offload tasks that may sleep to e.g. a=
> workqueue.
>
> Gr{oetje,eeting}s,
>
>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0Geert

I can try to do this - but - taking a spinlock and copying 8MB = framebuffer
would damage scheduling latency even for PCI framebuffer drivers.

Mikulas

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