Re: [PATCH 1/2] dmaengine: usb-dmac: Fix crash on runtime suspend

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Hello.

On 10/2/2015 4:00 AM, Yoshihiro Shimoda wrote:

If CONFIG_PREEMPT=y:

     Actually, it happens even with CONFIG_PREEMPT_VOLUNTARY=y.

      Unable to handle kernel NULL pointer dereference at virtual address 00000014
      pgd = c0003000
      [00000014] *pgd=80000040004003, *pmd=00000000
      Internal error: Oops: 206 [#1] PREEMPT SMP ARM
      Modules linked in:
      CPU: 0 PID: 17 Comm: kworker/0:1 Tainted: G        W       4.3.0-rc3-koelsch-022
      71-g705498fc5e6a5da8-dirty #1789
      Hardware name: Generic R8A7791 (Flattened Device Tree)
      Workqueue: pm pm_runtime_work
      task: ef578e40 ti: ef57a000 task.ti: ef57a000
      PC is at usb_dmac_chan_halt+0xc/0xc0
      LR is at usb_dmac_runtime_suspend+0x28/0x38
      pc : [<c023c880>]    lr : [<c023c95c>]    psr: 80000113
      sp : ef57bdf8  ip : 00000008  fp : 00000003
      r10: 00000008  r9 : c06ab928  r8 : ef49e810
      r7 : 00000000  r6 : 000000ac  r5 : ef770010  r4 : 00000000
      r3 : 00000000  r2 : 8ffc2b84  r1 : 00000000  r0 : ef770010
      Flags: Nzcv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment kernel
      Control: 30c5307d  Table: 40003000  DAC: fffffffd
      Process kworker/0:1 (pid: 17, stack limit = 0xef57a210)
      Stack: (0xef57bdf8 to 0xef57c000)

      [...

      [<c023c880>] (usb_dmac_chan_halt) from [<c023c95c>] (usb_dmac_runtime_suspend+0x28/0x38)
      [<c023c95c>] (usb_dmac_runtime_suspend) from [<c027b25c>] (pm_genpd_runtime_suspend+0x74/0x23c)

This happens because usb_dmac_probe() calls pm_runtime_put() before
usb_dmac_chan_probe(), leading to the device being suspended before the
DMA channels are initialized, causing a NULL pointer dereference.

Move the call to pm_runtime_put() to the end of usb_dmac_probe() to fix
this.

Add a check to usb_dmac_runtime_suspend() to prevent the crash from
happening in the error path.

Reported-by: Sergei Shtylyov <sergei.shtylyov@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>

I could not duplicate this issue completely on Lager.
Even if I enabled ealyprintk, I didn't see the panic log.
(Several kernel message appeared, and then the kernel hung.)

     I guess you also need to specify console=. The device tree console
assignment (from the "stdout-path" prop) happens too late, the console gets
switched to /dev/tty0 first. I forgot to mention that the pseudo-console
(CONFIG_VT) should be disabled as well.

Thank you for your comment!
I was able to look the panic log if I added specify console= in the bootargs.
(Even if CONFIG_VT=y, the log appeared.)

   Yeah, I got things somewhat mixed up, specifying console= alone should help.

MBR, Sergei

--
To unsubscribe from this list: send the line "unsubscribe dmaengine" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html



[Index of Archives]     [Linux Kernel]     [Linux ARM (vger)]     [Linux ARM MSM]     [Linux Omap]     [Linux Arm]     [Linux Tegra]     [Fedora ARM]     [Linux for Samsung SOC]     [eCos]     [Linux PCI]     [Linux Fastboot]     [Gcc Help]     [Git]     [DCCP]     [IETF Announce]     [Security]     [Linux MIPS]     [Yosemite Campsites]

  Powered by Linux