On Mon, Feb 29, 2016 at 07:46:35PM -1000, Jean-Denis Girard wrote: > Hello Josh, Hello, > Le 29/02/2016 06:18, Josh Cartwright a écrit : > > I think your best bet will be to try to get early console output, with > > the hope that you can get visibility into what is going wrong. I'm sure > > there are many tutorials out there on how to build a kernel with this > > serial debugging information. Do a search for DEBUG_LL, earlyprintk, > > and perhaps earlycon; these are not -rt specific. > > Thanks for your advice. I managed to obtain earlyprintk, this is what I got: Great, this helps a lot. > Uncompressing Linux... done, booting the kernel. > Booting Linux on physical CPU 0x0 > Linux version 4.4.3-rt9 (jdg@xxxxxxxxxxxxxxx) (gcc version 5.2.1 > 20151104 (Red Hat Cross 5.2.1-4) (GCC) ) #10 PREEMPT RT Mon Feb 29 > 13:01:47 TAHT 2016 > CPU: ARM926EJ-S [41069265] revision 5 (ARMv5TEJ), cr=0005317f > CPU: VIVT data cache, VIVT instruction cache > Machine model: Acme Systems Arietta G25 [..] > Unable to handle kernel NULL pointer dereference at virtual address 00000000 > pgd = c0004000 > [00000000] *pgd=00000000 > Internal error: Oops: 5 [#1] PREEMPT ARM > Modules linked in: > CPU: 0 PID: 0 Comm: swapper Not tainted 4.4.3-rt9 #10 > Hardware name: Atmel AT91SAM9 > task: c0537dd0 ti: c0534000 task.ti: c0534000 > PC is at try_to_wake_up+0x34/0x228 > LR is at kthread_create_on_node+0x94/0x134 [..] > [<c0030dfc>] (try_to_wake_up) from [<c002d084>] > (kthread_create_on_node+0x94/0x134) > [<c002d084>] (kthread_create_on_node) from [<c0040668>] > (setup_irq_thread+0x38/0xd4) > [<c0040668>] (setup_irq_thread) from [<c0041634>] (__setup_irq+0x1a8/0x648) > [<c0041634>] (__setup_irq) from [<c0041c3c>] > (request_threaded_irq+0xe4/0x144) > [<c0041c3c>] (request_threaded_irq) from [<c0520640>] > (of_at91_pmc_setup+0xe0/0x16c) > [<c0520640>] (of_at91_pmc_setup) from [<c05202bc>] (of_clk_init+0xf4/0x1b8) > [<c05202bc>] (of_clk_init) from [<c050c108>] (time_init+0x20/0x2c) > [<c050c108>] (time_init) from [<c050aafc>] (start_kernel+0x248/0x35c) > [<c050aafc>] (start_kernel) from [<20008048>] (0x20008048) > Code: e3c3303f e5932004 e2822001 e5832004 (e5902000) > ---[ end trace 0000000000000001 ]--- This confirms that the problem you are seeing is the same problem Alexandre and Boris solved in: https://www.spinics.net/lists/kernel/msg2172523.html It doesn't look like it's landed upstream yet (although it's been in next since last week). It looks like Alexandre has pushed a tag with these changes (destined for 4.6) at: git://git.kernel.org/pub/scm/linux/kernel/git/abelloni/linux.git at91-ab-4.6-drivers You can cherry-pick back those top 13 commits and give it a try. If you can confirm that those changes fix your problem, they should be considered for cherry-picking into 4.4-rt officially. Josh
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