On 12/15/2017 03:24 PM, Jan Kiszka wrote: > On 2017-12-14 20:44, Philippe Gerum wrote: >> On 12/14/2017 08:28 PM, Jan Kiszka wrote: >>> Hi Philippe, >>> >>> something got broken with the exception path rework: >>> >>> [ 2.619458] debug: unmapping init [mem >>> 0xffffffff81b43000-0xffffffff81ee5fff] >>> [ 2.622011] BUG: using __this_cpu_read() in preemptible [00000000] code: >>> init/1 >>> [ 2.623446] caller is __this_cpu_preempt_check+0x13/0x20 >>> [ 2.624724] CPU: 2 PID: 1 Comm: init Not tainted 4.4.105+ #689 >>> [ 2.626073] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS >>> rel-1.11.0-0-g63451fca13-prebuilt.qemu-project.org 04/01/2014 >>> [ 2.628911] I-pipe domain: Linux >>> [ 2.630083] ffffffff81993439 ffff88003fb43c10 ffffffff813afa45 >>> 0000000000000002 >>> [ 2.631427] ffff88003fb38000 ffff88003fb43c50 ffffffff813db5eb >>> ffffffff82c57340 >>> [ 2.631427] ffff88003fb43c98 0000000000000002 ffff88003fb44000 >>> 0000000000000000 >>> [ 2.631427] Call Trace: >>> [ 2.631427] [<ffffffff813afa45>] dump_stack+0xb2/0xdd >>> [ 2.631427] [<ffffffff813db5eb>] check_preemption_disabled+0x17b/0x1c0 >>> [ 2.631427] [<ffffffff813db663>] __this_cpu_preempt_check+0x13/0x20 >>> [ 2.631427] [<ffffffff8104eb1f>] do_page_fault+0x3f/0x60 >>> [ 2.631427] [<ffffffff8170f8b7>] page_fault+0x27/0x60 >>> [ 2.631427] [<ffffffff813bcef2>] ? __clear_user+0x42/0x70 >>> [ 2.631427] [<ffffffff813bcf69>] clear_user+0x49/0x80 >>> [ 2.631427] [<ffffffff812727d4>] padzero+0x24/0x40 >>> [ 2.631427] [<ffffffff81274bfe>] load_elf_binary+0x8fe/0x10f0 >>> [ 2.631427] [<ffffffff81116ee8>] ? ipipe_unstall_root+0x58/0x90 >>> [ 2.631427] [<ffffffff812222c7>] search_binary_handler+0x97/0x1d0 >>> [ 2.631427] [<ffffffff81223b86>] do_execveat_common.isra.40+0x5d6/0x7e0 >>> [ 2.631427] [<ffffffff81223aff>] ? >>> do_execveat_common.isra.40+0x54f/0x7e0 >>> [ 2.631427] [<ffffffff8122bb00>] ? path_openat+0x1440/0x14e0 >>> [ 2.631427] [<ffffffff816fff20>] ? rest_init+0xd0/0xd0 >>> [ 2.631427] [<ffffffff81223dbc>] do_execve+0x2c/0x30 >>> [ 2.631427] [<ffffffff810002eb>] run_init_process+0x2b/0x30 >>> [ 2.631427] [<ffffffff816fff5d>] kernel_init+0x3d/0xe0 >>> [ 2.631427] [<ffffffff8170d4c0>] ret_from_fork+0x40/0x70 >>> [ 2.631427] [<ffffffff816fff20>] ? rest_init+0xd0/0xd0 >>> >>> Unless you have some immediate idea, I will debug this tomorrow. Issue >>> disappears when I revert the related patches in the ipipe queue. >>> >> >> Issue may be in the changes affecting IPIPE_DO_TRAP() [4e180c151]. The >> sequence used to be prologue -> handler -> restore_root, it is now >> prologue -> restore_root -> handler, which basically means that the >> stall bit fixup is no more, ... a fixup. > > Right, this is broken. The previous code was well matured, it just > excluded the case int3 for dyn-ftrace, kprobe etc. so far. >
Actually, the code was broken with int3 as issued by ftrace. This is what triggered the change. > While gaining that support would be valuable, I would still recommend to > revert the changes for now and redesign the int3 handling carefully on top. > We should not be that far from a proper implementation. I'd like to try the kvm config that shows the issue. Is there any way to reproduce this easily? -- Philippe. _______________________________________________ Xenomai mailing list Xenomai@xenomai.org https://xenomai.org/mailman/listinfo/xenomai
