On Fri, Jun 24, 2016 at 11:11:47AM -0700, Linus Torvalds wrote: > On Fri, Jun 24, 2016 at 10:51 AM, Linus Torvalds > <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > > > > And in particular, the init_task stack initialization initialized it > > to the init_thread pointer. Which was definitely deadly. > > > > Let's see if that was it.. > > No, it's still broken. But it's *less* broken, so here's a new version > of the patch that at least gets some of the stack setup right, in my > hope that somebody will bother to look at this, and being less broken > might mean that somebody sees what else I missed.. I found at least one bug. The changing of task->stack from a "void *" to an "unsigned long *": > - void *stack; > + unsigned long *stack; That subtly changes the pointer arithmetic in do_boot_cpu(): idle->thread.sp = (unsigned long) (((struct pt_regs *) (THREAD_SIZE + task_stack_page(idle))) - 1); That ends up adding 128k to the stack page bottom instead of 16k. But fixing that doesn't seem to fix this: [18446743832.576241] ------------[ cut here ]------------ [18446743832.576241] WARNING: CPU: 1 PID: 0 at /home/jpoimboe/git/linux/arch/x86/kernel/cpu/common.c:1434 cpu_init+0x34b/0x440 [18446743832.576241] Modules linked in: [18446743832.576241] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.7.0-rc4+ #47 [18446743832.576241] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.8.1-20150318_183358- 04/01/2014 [18446743832.576241] 0000000000000086 574e5e6c6855ace9 ffff88007c553e88 ffffffff8143cb83 [18446743832.576241] 0000000000000000 0000000000000000 ffff88007c553ec8 ffffffff810b0e7b [18446743832.576241] 0000059a00000000 0000000000000000 0000000000000000 0000000000000000 [18446743832.576241] Call Trace: [18446743832.576241] [<ffffffff8143cb83>] dump_stack+0x85/0xc2 [18446743832.576241] [<ffffffff810b0e7b>] __warn+0xcb/0xf0 [18446743832.576241] [<ffffffff810b0fad>] warn_slowpath_null+0x1d/0x20 [18446743832.576241] [<ffffffff810491bb>] cpu_init+0x34b/0x440 [18446743832.576241] [<ffffffff8105ab7c>] start_secondary+0x1c/0x1a0 [18446743832.576241] ---[ end trace 924d57afbaca0720 ]--- So there's at least another bug lurking.. -- Josh -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
