Re: [PATCHv4 2/2] mm: use stack_depot_early_init for kmemleak

Mike Rapoport
2023-01-20T05:26:20Z

On Thu, Jan 19, 2023 at 09:22:25AM +0800, zhaoyang.huang wrote:
> From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
>
> Mirsad report bellow error which caused by stack_depot_init failed in kvcalloc.
> Solve this by having stackdepot use stack_depot_early_init.
>
> On 1/4/23 17:08, Mirsad Goran Todorovac wrote:
> I hate to bring bad news again, but there seems to be a problem with the output of /sys/kernel/debug/kmemleak:
>
> [root@pc-mtodorov ~]# cat /sys/kernel/debug/kmemleak
> unreferenced object 0xffff951c118568b0 (size 16):
> comm "kworker/u12:2", pid 56, jiffies 4294893952 (age 4356.548s)
> hex dump (first 16 bytes):
> 6d 65 6d 73 74 69 63 6b 30 00 00 00 00 00 00 00 memstick0.......
> backtrace:
> [root@pc-mtodorov ~]#
>
> Apparently, backtrace of called functions on the stack is no longer printed with the list of memory leaks.
> This appeared on Lenovo desktop 10TX000VCR, with AlmaLinux 8.7 and BIOS version M22KT49A (11/10/2022)
> and 6.2-rc1 and 6.2-rc2 builds.
> This worked on 6.1 with the same CONFIG_KMEMLEAK=y and MGLRU enabled on a vanilla mainstream kernel
> from Mr. Torvalds' tree. I don't know if this is deliberate feature for some reason or a bug.
> Please find attached the config, lshw and kmemleak output.
>
> reported-by: Mirsad Todorovac <mirsad.todorovac@alu.unizg.hr>
> suggested-by: Vlastimil Babka <vbabka@suse.cz>
> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>

Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>

> ---
> v2: use stack_depot_want_early_init instead of CONFIG_STACKDEPOT_ALWAYS_INIT
> v3: have the Kconfig changes commited in another patch
> v4: select CONFIG_STACKDEPOT_ALWAYS_INIT when DEBUG_KMEMLEAK_DEFAULT_OFF is off
> ---
>
> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
> ---
> mm/Kconfig.debug | 1 +
> mm/kmemleak.c | 4 +++-
> 2 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
> index d1893ac..466a37e 100644
> --- a/mm/Kconfig.debug
> +++ b/mm/Kconfig.debug
> @@ -219,6 +219,7 @@ config DEBUG_KMEMLEAK
> select KALLSYMS
> select CRC32
> select STACKDEPOT
> + select STACKDEPOT_ALWAYS_INIT if !DEBUG_KMEMLEAK_DEFAULT_OFF
> help
> Say Y here if you want to enable the memory leak
> detector. The memory allocation/freeing is traced in a way
> diff --git a/mm/kmemleak.c b/mm/kmemleak.c
> index 762b91f..ddc1ddf 100644
> --- a/mm/kmemleak.c
> +++ b/mm/kmemleak.c
> @@ -2070,8 +2070,10 @@ static int __init kmemleak_boot_config(char *str)
> return -EINVAL;
> if (strcmp(str, "off") == 0)
> kmemleak_disable();
> - else if (strcmp(str, "on") == 0)
> + else if (strcmp(str, "on") == 0) {
> kmemleak_skip_disable = 1;
> + stack_depot_want_early_init();
> + }
> else
> return -EINVAL;
> return 0;
> --
> 1.9.1
>
>

--
Sincerely yours,
Mike.