Re: [PATCH 3/3] mips: ralink: mt7621: do not use kzalloc too early

[Thomas Bogendoerfer]

On Mon, Nov 14, 2022 at 11:56:58AM +1000, John Thomson wrote:
> With CONFIG_SLUB=y, following commit 6edf2576a6cc ("mm/slub: enable
> debugging memory wasting of kmalloc") mt7621 failed to boot very early,
> without showing any console messages.
> This exposed the pre-existing bug of mt7621.c using kzalloc before normal
> memory management was available.
> Prior to this slub change, there existed the unintended protection against
> "kmem_cache *s" being NULL as slab_pre_alloc_hook() happened to
> return NULL and bailed out of slab_alloc_node().
> This allowed mt7621 prom_soc_init to fail in the soc_dev_init kzalloc,
> but continue booting without the SOC_BUS driver device registered.
> 
> Console output from a DEBUG_ZBOOT vmlinuz kernel loading,
> with mm/slub modified to warn on kmem_cache zero or null:
> 
> zimage at:     80B842A0 810B4BC0
> Uncompressing Linux at load address 80001000
> Copy device tree to address  80B80EE0
> Now, booting the kernel...
> 
> [    0.000000] Linux version 6.1.0-rc3+ (john@john)
> (mipsel-buildroot-linux-gnu-gcc.br_real (Buildroot
> 2021.11-4428-g6b6741b) 12.2.0, GNU ld (GNU Binutils) 2.39) #73 SMP Wed
>      Nov  2 05:10:01 AEST 2022
> [    0.000000] ------------[ cut here ]------------
> [    0.000000] WARNING: CPU: 0 PID: 0 at mm/slub.c:3416
> kmem_cache_alloc+0x5a4/0x5e8
> [    0.000000] Modules linked in:
> [    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 6.1.0-rc3+ #73
> [    0.000000] Stack : 810fff78 80084d98 00000000 00000004 00000000
> 00000000 80889d04 80c90000
> [    0.000000]         80920000 807bd328 8089d368 80923bd3 00000000
> 00000001 80889cb0 00000000
> [    0.000000]         00000000 00000000 807bd328 8084bcb1 00000002
> 00000002 00000001 6d6f4320
> [    0.000000]         00000000 80c97d3d 80c97d68 fffffffc 807bd328
> 00000000 00000000 00000000
> [    0.000000]         00000000 a0000000 80910000 8110a0b4 00000000
> 00000020 80010000 80010000
> [    0.000000]         ...
> [    0.000000] Call Trace:
> [    0.000000] [<80008260>] show_stack+0x28/0xf0
> [    0.000000] [<8070c958>] dump_stack_lvl+0x60/0x80
> [    0.000000] [<8002e184>] __warn+0xc4/0xf8
> [    0.000000] [<8002e210>] warn_slowpath_fmt+0x58/0xa4
> [    0.000000] [<801c0fac>] kmem_cache_alloc+0x5a4/0x5e8
> [    0.000000] [<8092856c>] prom_soc_init+0x1fc/0x2b4
> [    0.000000] [<80928060>] prom_init+0x44/0xf0
> [    0.000000] [<80929214>] setup_arch+0x4c/0x6a8
> [    0.000000] [<809257e0>] start_kernel+0x88/0x7c0
> [    0.000000]
> [    0.000000] ---[ end trace 0000000000000000 ]---
> [    0.000000] SoC Type: MediaTek MT7621 ver:1 eco:3
> [    0.000000] printk: bootconsole [early0] enabled
> 
> Allowing soc_device_register to work exposed oops in the mt7621 phy pci,
> and pci controller drivers from soc_device_match_attr, due to missing
> sentinels in the quirks tables. These were fixed with:
> commit 819b885cd886 ("phy: ralink: mt7621-pci: add sentinel to quirks
> table")
> not yet applied ("PCI: mt7621: add sentinel to quirks table")
> 
> Link: https://lore.kernel.org/linux-mm/becf2ac3-2a90-4f3a-96d9-a70f67c66e4a@xxxxxxxxxxxxxxxx/
> Fixes: 71b9b5e0130d ("MIPS: ralink: mt7621: introduce 'soc_device' initialization")
> Signed-off-by: John Thomson <git@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
> ---
>  arch/mips/ralink/mt7621.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)

applied to mips-next.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]