On Thu, 17 Sep 2015, Steven Rostedt wrote:

On Thu, 17 Sep 2015 12:13:15 +0200 (CEST)
Thomas Gleixner [off-list ref] wrote:

quoted

Digging deeper. My assumption that it's a post powerpc merge failure
turned out to be wrong.

Does 4.2 have the problem?

No. Neither does 

4c92b5bb1422: Merge branch 'pcmcia' of git://ftp.arm.linux.org.uk/~rmk/linux-arm
 

If it's a corruption of the mcount tables, it could be specific on what
the compiler does. That is, the working of one kernel to the other, may
only depend on how gcc compiled something. Have you tried different
compilers? Maybe one version of gcc may work over another?

It just results in a different failure mode. Instead of silently
hanging I get:

[    2.248275] Oops: Exception in kernel mode, sig: 4 [#1]
[    2.253633] PREEMPT lite5200
[    2.256584] Modules linked in:
[    2.259723] CPU: 0 PID: 1 Comm: swapper Not tainted 4.3.0-rc1-51179-gae80a2f-dirty #75
[    2.267815] task: c383c000 ti: c383a000 task.ti: c383a000
[    2.273330] NIP: c00e1eec LR: c00df0f4 CTR: 00000000
[    2.278405] REGS: c383bcd0 TRAP: 0700   Not tainted  (4.3.0-rc1-51179-gae80a2f-dirty)
[    2.286396] MSR: 00089032 <EE,ME,IR,DR,RI>  CR: 44824028  XER: 00000000
[    2.293187] 
GPR00: c00def84 c383bd80 c383c000 c3084000 bffffff1 00677595 c383bdd8 00000000 
GPR08: 00000001 00000001 00000400 00000002 24828022 00000000 c0004254 84822042 
GPR16: 20000000 44822042 fffff000 c3086ffc c06ce248 c383a000 c3082000 c06d0000 
GPR24: c383a000 00000ffc 00677595 bffffff1 c3084000 c3015bfc 00000017 c3086000 
[    2.323656] NIP [c00e1eec] vm_normal_page+0x0/0xdc
[    2.328560] LR [c00df0f4] follow_page_mask+0x260/0x4fc
[    2.333807] Call Trace:
[    2.336321] [c383bd80] [c00def84] follow_page_mask+0xf0/0x4fc (unreliable)
[    2.343360] [c383bdd0] [c00df4a4] __get_user_pages.part.28+0x114/0x3e0
[    2.350050] [c383be30] [c010e788] copy_strings+0x16c/0x2c8
[    2.355668] [c383bea0] [c010e91c] copy_strings_kernel+0x38/0x50
[    2.361730] [c383bec0] [c011057c] do_execveat_common+0x440/0x658
[    2.367877] [c383bf10] [c01107cc] do_execve+0x38/0x48
[    2.373056] [c383bf20] [c00039f0] try_to_run_init_process+0x24/0x64
[    2.379469] [c383bf30] [c000430c] kernel_init+0xb8/0x10c
[    2.384924] [c383bf40] [c0010c40] ret_from_kernel_thread+0x5c/0x64
[    2.391242] --- interrupt: 0 at   (null)
[    2.391242]     LR =   (null)
[    2.398263] Instruction dump:
[    2.401297] 01000000 00037000 00000000 00000000 f0000000 00000001 0a641e09 acde4823 
[    2.409237] 000f0000 179a7b00 07de2900 03ef1480 <01f78a40> 0001c200 60000000 9421fff0 
[    2.417375] ---[ end trace 996fd312ce9c18ce ]---

Again, if I disable CONFIG_TRACER its gone.

Thanks,

	tglx