Re: MIPS: ath79: regression after patch: sched/fair: do not expose some tracepoints to user if CONFIG_SCHEDSTATS is not set

[Yafang Shao <laoar.shao@gmail.com>]

On Fri, Jun 14, 2019 at 12:02 AM Oleksij Rempel <o.rempel@pengutronix.de> wrote:
>
> On Thu, Jun 13, 2019 at 04:12:57PM +0800, Yafang Shao wrote:
> > On Thu, Jun 13, 2019 at 4:08 PM Yafang Shao <laoar.shao@gmail.com> wrote:
> > >
> > > On Thu, Jun 13, 2019 at 2:30 PM Oleksij Rempel <o.rempel@pengutronix.de> wrote:
> > > >
> > > > Hi,
> > > >
> > > > After patch:
> > > > -----------------------------------------------------
> > > > commit 2a09b5de235a6b5f76193a2ed46546a2944f98bf
> > > > Author: Yafang Shao <laoar.shao@gmail.com>
> > > > Date:   Tue Mar 26 20:13:10 2019 +0800
> > > >     sched/fair: do not expose some tracepoints to user if CONFIG_SCHEDSTATS is not set
> > > >
> > > >     The tracepoints trace_sched_stat_{iowait, blocked, wait, sleep} should
> > > >     be not exposed to user if CONFIG_SCHEDSTATS is not set.
> > > >
> > > >     Link: http://lkml.kernel.org/r/1553602391-11926-3-git-send-email-laoar.shao@gmail.com
> > > >
> > > >     Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > > >     Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> > > >     Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> > > > -----------------------------------------------------
> > > >
> > > > i can't boot kernel on MIPS based system Atheros ar9331. The boot
> > > > process ends with following oops:
> > > > -----------------------------------------------------
> > > > [    0.000000] Built 1 zonelists, mobility grouping on.  Total pages: 16256                                                                                                [0/1518]
> > > > [    0.000000] Kernel command line:   ip=dhcp root=/dev/nfs nfsroot=192.168.23.4:/home/ore/nfsroot/dpt-module,v3,tcp
> > > > [    0.000000] Dentry cache hash table entries: 8192 (order: 3, 32768 bytes)
> > > > [    0.000000] Inode-cache hash table entries: 4096 (order: 2, 16384 bytes)
> > > > [    0.000000] Writing ErrCtl register=00000000
> > > > [    0.000000] Readback ErrCtl register=00000000
> > > > [    0.000000] Memory: 56376K/65536K available (5376K kernel code, 437K rwdata, 1068K rodata, 1432K init, 214K bss, 9160K reserved, 0K cma-reserved)
> > > > [    0.000000] random: get_random_u32 called from cache_random_seq_create+0x9c/0x170 with crng_init=0
> > > > [    0.000000] SLUB: HWalign=32, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
> > > > [    0.000000] ftrace: allocating 18167 entries in 36 pages
> > > > [    0.000000] CPU 0 Unable to handle kernel paging request at virtual address 00000000, epc == 00000000, ra == 00000000
> > > > [    0.000000] Oops[#1]:
> > > > [    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 5.2.0-rc4+ #308
> > > > [    0.000000] $ 0   : 00000000 8007e5fc 00000003 00000002
> > > > [    0.000000] $ 4   : 00000001 00000000 00000000 83c22470
> > > > [    0.000000] $ 8   : 00000000 00000000 00000000 00000000
> > > > [    0.000000] $12   : 806afe04 00000000 00000001 00000000
> > > > [    0.000000] $16   : 800adc0c 800adc00 00000000 00000000
> > > > [    0.000000] $20   : 00000000 0000048e 00000000 806c0000
> > > > [    0.000000] $24   : 00000003 800619e4
> > > > [    0.000000] $28   : 806ae000 806afe10 808b0000 00000000
> > > > [    0.000000] Hi    : 00000000
> > > > [    0.000000] Lo    : 00000000
> > > > [    0.000000] epc   : 00000000 0x0
> > > > [    0.000000] ra    : 00000000 0x0
> > > > [    0.000000] Status: 10000002 KERNEL EXL
> > > > [    0.000000] Cause : 10800008 (ExcCode 02)
> > > > [    0.000000] BadVA : 00000000
> > > > [    0.000000] PrId  : 00019374 (MIPS 24Kc)
> > > > [    0.000000] Modules linked in:
> > > > [    0.000000] Process swapper (pid: 0, threadinfo=(ptrval), task=(ptrval), tls=00000000)
> > > > [    0.000000] Stack : 00000002 8007e784 806ca284 00000000 800adc0c 00000000 80070eb0 8007108c
> > > > [    0.000000]         83c03c00 801ab7d8 83c03b80 00000000 00000000 83c03b80 00000000 801109cc
> > > > [    0.000000]         00000001 80880000 80880000 800c1318 00000000 ffffffff 806b0000 806b0000
> > > > [    0.000000]         83c22470 0000048e 8075eb00 807706dc 806b0000 80753158 806b0000 80755209
> > > > [    0.000000]         00000001 80880000 80880000 80726cc8 ffffffff 000046f7 00000024 00000003
> > > > [    0.000000]         ...
> > > > [    0.000000] Call Trace:
> > > > [    0.000000]
> > > > [    0.000000] [<8007e784>] r4k_flush_icache_range+0x10/0x18
> > > > [    0.000000] [<800adc0c>] preempt_count_sub+0x10/0xe4
> > > > [    0.000000] [<80070eb0>] ftrace_caller+0x0/0x54
> > > > [    0.000000] [<8007108c>] ftrace_make_nop+0x8c/0x94
> > > > [    0.000000] [<801ab7d8>] __get_free_pages+0x2c/0x60
> > > > [    0.000000] [<801109cc>] ftrace_process_locs+0x364/0x3ec
> > > > [    0.000000] [<800c1318>] vprintk_default+0x34/0x40
> > > > [    0.000000] [<80726cc8>] ftrace_init+0xb8/0x138
> > > > [    0.000000] [<8071ac98>] start_kernel+0x290/0x584
> > > > [    0.000000] [<8071a368>] unknown_bootoption+0x0/0x270
> > > > [    0.000000]
> > > > [    0.000000] Code: (Bad address in epc)
> > > > [    0.000000]
> > > > [    0.000000] ---[ end trace 64e6fa591c4a277c ]---
> > > > [    0.000000] Kernel panic - not syncing: Fatal exception
> > > > [    0.000000] Rebooting in
> > > > -----------------------------------------------------
> > > >
> > > > After reverting this patch I can normally boot the kernel.
> > > > The kernel is build with CONFIG_SCHEDSTATS not set.
> > > >
> > > > --
> > > > Pengutronix e.K.                           |                             |
> > > > Industrial Linux Solutions                 | http://www.pengutronix.de/  |
> > > > Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
> > > > Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |
> > >
> > > Hi Oleksij,
> > >
> > > This really makes me confused.
> > > If CONFIG_SCHEDSTATS is not set,  trace_sched_stat_{iowait, blocked,
> > > wait, sleep} will be optimized out by
> > > the compiler. That should not effect other codes.
> > >
> > > Would you pls. try bellow command on your build server?
> > > $ objdump -dr kernel/sched/fair.o | awk '/>:$/ { F=$2 } /sched_stat/ {
> > > print F " " $0 }'
> > >
> >
> > Plus, could you pls. show me the  difference on the objdump of these
> > two vmlinux (with and without my patch) ?
>
> Both files are in attachment.
>

Hi Oleksij,

Unfortunately I don't have a mips toolchain on hand.
It would be better if you could give me the  disassembled code of
these two vmlinuxs.
I will try to build a cross toolchain for MIPS 24Kc, that may take some time.

Thanks
Yafang