Hi Sergei-san, > Sent: Thursday, October 01, 2015 9:27 PM > > 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. 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.) > > 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. :-) You're welcome! And, thank you for the report. Best regards, Yoshihiro Shimoda > > 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 -- 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
