On Sun, Oct 25, 2015 at 11:09:33AM +0100, Geert Uytterhoeven wrote: > If CONFIG_PREEMPT=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. This worked, applied both now Thanks -- ~Vinod -- 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
