Hello. On 10/1/2015 1:53 PM, 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.
Anyway, I tested this patch that kernel could boot correctly even if CONFIG_PREEMPT=y. So, Tested-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
Thank you. :-)
Best regards, Yoshihiro Shimoda
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
