答复: 答复: INFO: [BISECTED] Regression: A Problem with /sys/kernel/debug/kmemleak output: backtrace not printed since 6.2.0-rc1

黄朝阳 (Zhaoyang Huang)
2023-01-13T10:16:50Z

>On 13.1.2023. 7:20, 黄朝阳 (Zhaoyang Huang) wrote:
>>> /sys/kernel/debug/kmemleak output: backtrace not printed since
>>> 6.2.0-rc1
>>>
>>>
>>>> On 12. 01. 2023. 20:50, Mirsad Todorovac wrote:
>>>>> Hi all,
>>>>>
>>>>> 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.
>>>>>
>>>>> The bisection gave this commit as the culprit for the severed stack
>>>>> backtrace print in /sys/kernel/debug/kmemleak:
>>>>>
>>>>> mtodorov@domac:~/linux/kernel/linux_torvalds$ git bisect good
>>>>> 56a61617dd2276cbc56a6c868599716386d70041 is the first bad commit
>>>>> commit 56a61617dd2276cbc56a6c868599716386d70041
>>>>> Author: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
>>>>> Date: Thu Oct 27 17:50:24 2022 +0800
>>>>>
>>>>> mm: use stack_depot for recording kmemleak's backtrace
>>>>>
>>>>> Using stack_depot to record kmemleak's backtrace which has
>been
>>>>> implemented on slub for reducing redundant information.
>>>>>
>>>>> The complete bisect log is:
>>>>>
>>>>> mtodorov@domac:~/linux/kernel/linux_torvalds$ git bisect log git
>>>>> bisect start '--' 'mm'
>>>>> # good: [830b3c68c1fb1e9176028d02ef86f3cf76aa2476] Linux 6.1 git
>>>>> bisect good 830b3c68c1fb1e9176028d02ef86f3cf76aa2476
>>>>> # bad: [1b929c02afd37871d5afb9d498426f83432e71c2] Linux 6.2-rc1 git
>>>>> bisect bad 1b929c02afd37871d5afb9d498426f83432e71c2
>>>>> # good: [8b9ed79c2d587bec5f603d66801478a5af9af842] Merge tag
>>>>> 'x86_asm_for_v6.2' of
>>>>> git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
>>>>> git bisect good 8b9ed79c2d587bec5f603d66801478a5af9af842
>>>>> # good: [e83b39d6bbdb6d25bd6f5c258832774635d29b47] mm: make
>>>>> drop_caches keep reclaiming on all nodes git bisect good
>>>>> e83b39d6bbdb6d25bd6f5c258832774635d29b47
>>>>> # good: [9997bc017549acd6425e32300eff28424ffeeb6b] zsmalloc:
>>>> implement
>>>>> writeback mechanism for zsmalloc git bisect good
>>>>> 9997bc017549acd6425e32300eff28424ffeeb6b
>>>>> # good: [6287b7dae80944bfa37784a8f9d6861a4facaa6e] mm,thp,rmap:
>fix
>>>>> races between updates of subpages_mapcount git bisect good
>>>>> 6287b7dae80944bfa37784a8f9d6861a4facaa6e
>>>>> # good: [8fa590bf344816c925810331eea8387627bbeb40] Merge tag
>>>>> 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
>>>>> git bisect good 8fa590bf344816c925810331eea8387627bbeb40
>>>>> # good: [4f292c4de4f6fb83776c0ff22674121eb6ddfa2f] Merge tag
>>>>> 'x86_mm_for_6.2_v2' of
>>>>> git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
>>>>> git bisect good 4f292c4de4f6fb83776c0ff22674121eb6ddfa2f
>>>>> # bad: [1ea9d333ba475041efe43d9d9bc32e64aea2ea2b] Merge tag
>>>>> 'mm-stable-2022-12-17-2' of
>>>>> git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
>>>>> git bisect bad 1ea9d333ba475041efe43d9d9bc32e64aea2ea2b
>>>>> # bad: [56a61617dd2276cbc56a6c868599716386d70041] mm: use
>>>> stack_depot
>>>>> for recording kmemleak's backtrace git bisect bad
>>>>> 56a61617dd2276cbc56a6c868599716386d70041
>>>>> # good: [61b963b52f59524e27692bc1c14bfb2459e32eb3] mm/gup_test:
>>>> free
>>>>> memory allocated via kvcalloc() using kvfree() git bisect good
>>>>> 61b963b52f59524e27692bc1c14bfb2459e32eb3
>>>>> # first bad commit: [56a61617dd2276cbc56a6c868599716386d70041]
>mm:
>>>> use
>>>>> stack_depot for recording kmemleak's backtrace # good:
>>>>> [9102b78b6f6ae6af3557114c265c266b312c1319] maple_tree: update
>>>>> copyright dates for test code git bisect good
>>>>> 9102b78b6f6ae6af3557114c265c266b312c1319
>>>>> # first bad commit: [56a61617dd2276cbc56a6c868599716386d70041]
>mm:
>>>> use
>>>>> stack_depot for recording kmemleak's backtrace You have mail in
>>>>> /var/mail/mtodorov mtodorov@domac:~/linux/kernel/linux_torvalds$
>>>>>
>>>>> The platform is 10TX000VCR
>>>> (LENOVO_MT_10TX_BU_Lenovo_FM_V530S-07ICB)
>>>>> running AlmaLinux 8.7 (CentOS clone) and BIOS M22KT49A.
>>>>>
>>>>> GCC used was:
>>>>>
>>>>> mtodorov@domac:~/linux/kernel/linux_torvalds$ gcc --version gcc
>>>>> (Debian 8.3.0-6) 8.3.0 Copyright (C) 2018 Free Software Foundation,
>>>>> Inc.
>>>>> This is free software; see the source for copying conditions.
>>>>> There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
>>>> PARTICULAR PURPOSE.
>>>>> mtodorov@domac:~/linux/kernel/linux_torvalds$
>>>>>
>>>>> Hope this helps.
>>>>>
>>>>> I lack the insight to pinpoint the exact fault in the patch.
>>>>
>>>> P.S.
>>>>
>>>> To further complicate things, on Ubuntu 22.10 Lenovo Ideapad 3
>>>> 15ITL6 laptop the kmemleak stack backtrace is printed correctly with
>>>> the same kernels (but .deb instead of .rpm for the same build):
>>>>
>>>> unreferenced object 0xffff94ca88e042d0 (size 80):
>>>> comm "thermald", pid 768, jiffies 4294893592 (age 78581.504s)
>>>> hex dump (first 32 bytes):
>>>> 00 00 00 00 00 00 00 00 0d 01 2d 00 00 00 00 00 ..........-.....
>>>> af 07 01 80 fd ac ff ff 00 00 00 00 00 00 00 00 ................
>>>> backtrace:
>>>> [<ffffffffa0dcb921>] slab_post_alloc_hook+0x91/0x320
>>>> [<ffffffffa0dcfb79>] kmem_cache_alloc+0x169/0x2f0
>>>> [<ffffffffa12b1def>] acpi_os_acquire_object+0x2c/0x32
>>>> [<ffffffffa12b1ea2>] acpi_ps_alloc_op+0x4a/0x99
>>>> [<ffffffffa12af5c8>] acpi_ps_get_next_arg+0x611/0x761
>>>> [<ffffffffa12afbbc>] acpi_ps_parse_loop+0x494/0x8d7
>>>> [<ffffffffa12b1434>] acpi_ps_parse_aml+0x1bb/0x561
>>>> [<ffffffffa12b24c8>] acpi_ps_execute_method+0x20f/0x2d5
>>>> [<ffffffffa12a7acf>] acpi_ns_evaluate+0x34d/0x4f3
>>>> [<ffffffffa12ad6a3>] acpi_evaluate_object+0x180/0x3ae
>>>> [<ffffffffa1269ca8>] acpi_run_osc+0x128/0x250
>>>> [<ffffffffc0bbb14f>] int3400_thermal_run_osc+0x6f/0xc0
>>>> [int3400_thermal]
>>>> [<ffffffffc0bbb293>] current_uuid_store+0xe3/0x120
>[int3400_thermal]
>>>> [<ffffffffa13b8ed4>] dev_attr_store+0x14/0x30
>>>> [<ffffffffa0ee0458>] sysfs_kf_write+0x38/0x50
>>>> [<ffffffffa0edf516>] kernfs_fop_write_iter+0x146/0x1d0 You have
>>>> new mail in /var/mail/root
>>>> root@marvin-IdeaPad-3-15ITL6:/home/marvin#
>>>>
>>>> Regards,
>>>> Mirsad
>>>
>>> thanks for head up. Could you please help to check If
>>> CONFIG_STACKTRACE and CONFIG_STACKDEPOT is enabled on the fault
>kernel?
>> Please try the patch below if the configs are right. I think it should
>> be caused by the late ready for kmemleak
>>
>> commit 556eb1927da99ab366e370d593fc32da946768c3
>> Author: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
>> Date: Fri Jan 13 14:13:39 2023 +0800
>>
>> mm: instroduce a flag to indicate stack_depot's ready
>>
>> try to solve the kmemleak's late ready issue.
>>
>> diff --git a/mm/kmemleak.c b/mm/kmemleak.c index 762b91f..7eb24bc
>> 100644
>> --- a/mm/kmemleak.c
>> +++ b/mm/kmemleak.c
>> @@ -216,6 +216,7 @@ struct kmemleak_object { static int
>kmemleak_warning;
>> /* set if a fatal kmemleak error has occurred */ static int
>> kmemleak_error;
>> +static int kmemleak_stadep_initialized;
>>
>> /* minimum and maximum address that may be valid pointers */ static
>unsigned long min_addr = ULONG_MAX; @@ -601,7 +602,7 @@ static noinline
>depot_stack_handle_t set_track_prepare(void)
>> unsigned long entries[MAX_TRACE];
>> unsigned int nr_entries;
>>
>> - if (!kmemleak_initialized)
>> + if (!kmemleak_stadep_initialized)
>> return 0;
>> nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 3);
>> trace_handle = stack_depot_save(entries, nr_entries,
>GFP_NOWAIT); @@ -2110,6 +2111,7 @@ void __init kmemleak_init(void)
>> create_object((unsigned long)__start_ro_after_init,
>> __end_ro_after_init -
>__start_ro_after_init,
>> KMEMLEAK_GREY, GFP_ATOMIC);
>> + kmemleak_stadep_initialized = 1;
>> }
>
>Hi, Zhaoyang,
>
>Sorry, applied the patch and rebuilt, but it didn't work for me:
>
>[root@pc-mtodorov marvin]# uname -rms
>Linux 6.2.0-rc3-mglru-kmemlk-patch-zhaoyang1+ x86_64 [root@pc-mtodorov
>marvin]# cat /sys/kernel/debug/kmemleak [root@pc-mtodorov marvin]# echo
>scan | tee !$ echo scan | tee /sys/kernel/debug/kmemleak scan
>[root@pc-mtodorov marvin]# cat /sys/kernel/debug/kmemleak unreferenced
>object 0xffff98938fed1ee0 (size 16):
> comm "kworker/u12:2", pid 57, jiffies 4294894053 (age 66.616s)
> 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 marvin]#
>
>Still the stack backtrace list is severed.
>CONFIG_STACKDEPOT and CONFIG_STACKTRACE are both "=y":
>
>[root@pc-mtodorov marvin]# grep -E 'CONFIG_(STACKTRACE|STACKDEPOT)'
>/boot/config-6.2.0-rc3-mglru-kmemlk-patch-zhaoyang1+
>CONFIG_STACKTRACE_SUPPORT=y
>CONFIG_STACKDEPOT=y
># CONFIG_STACKTRACE_BUILD_ID is not set
>CONFIG_STACKTRACE=y
>[root@pc-mtodorov marvin]#
>
>Your patch was successfully applied (after some tweaks):
>
>mtodorov@domac:~/linux/kernel/linux_torvalds$ git diff mm diff --git
>a/mm/kmemleak.c b/mm/kmemleak.c index 92f670edbf51..78fd3b89b057
>100644
>--- a/mm/kmemleak.c
>+++ b/mm/kmemleak.c
>@@ -216,6 +216,7 @@ static int kmemleak_initialized;
> static int kmemleak_warning;
> /* set if a fatal kmemleak error has occurred */
> static int kmemleak_error;
>+static int kmemleak_stadep_initialized;
>
> /* minimum and maximum address that may be valid pointers */
> static unsigned long min_addr = ULONG_MAX; @@ -601,7 +602,7 @@ static
>noinline depot_stack_handle_t set_track_prepare(void)
> unsigned long entries[MAX_TRACE];
> unsigned int nr_entries;
>
>- if (!kmemleak_initialized)
>+ if (!kmemleak_stadep_initialized)
> return 0;
> nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 3);
> trace_handle = stack_depot_save(entries, nr_entries,
>GFP_NOWAIT); @@ -2110,6 +2111,7 @@ void __init kmemleak_init(void)
> create_object((unsigned long)__start_ro_after_init,
> __end_ro_after_init -
>__start_ro_after_init,
> KMEMLEAK_GREY, GFP_ATOMIC);
>+ kmemleak_stadep_initialized = 1;
> }
>
> /*
>mtodorov@domac:~/linux/kernel/linux_torvalds$
>
>Please verify that the above is correct.
It is correct. Another reason could be the stack is less than 3 layers which could be surpassed by stack_trace_save. Could you please try to modify the code as bellow and try again.
static noinline depot_stack_handle_t set_track_prepare(void)
{
depot_stack_handle_t trace_handle;
unsigned long entries[MAX_TRACE];
unsigned int nr_entries;

if (!kmemleak_initialized)
return 0;
- nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 3);
+ nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0);
trace_handle = stack_depot_save(entries, nr_entries, GFP_NOWAIT);

return trace_handle;
}

>
>Regards,
>Mirsad
>
>--
>Mirsad Todorovac
>System engineer
>Faculty of Graphic Arts | Academy of Fine Arts University of Zagreb Republic of
>Croatia, the European Union
>--
>Sistem inženjer
>Grafički fakultet | Akademija likovnih umjetnosti Sveučilište u Zagrebu