回复: [PATCH] mm,oom_reaper: avoid run queue_oom_reaper if task is not oom

[gaoxu <gaoxu2@hihonor.com>]

On Web, 22 Nov 2023 21:47:44 +0000 Andrew Morton wrote:
> On Wed, 22 Nov 2023 12:46:44 +0000 gaoxu <gaoxu2@hihonor.com> wrote:

>> The function queue_oom_reaper tests and sets tsk->signal->oom_mm->flags.
>> However, it is necessary to check if 'tsk' is an OOM victim before 
>> executing 'queue_oom_reaper' because the variable may be NULL.
>> 
>> We encountered such an issue, and the log is as follows:
>> [3701:11_see]Out of memory: Killed process 3154 (system_server) 
>> total-vm:23662044kB, anon-rss:0kB, file-rss:0kB, shmem-rss:0kB,
>> UID:1000 pgtables:4056kB oom_score_adj:-900
>> [3701:11_see][RB/E]rb_sreason_str_set: sreason_str set null_pointer
>> [3701:11_see][RB/E]rb_sreason_str_set: sreason_str set unknown_addr 
>> [3701:11_see]Unable to handle kernel NULL pointer dereference at 
>> virtual address 0000000000000328

> Well that isn't good.  How frequently does this happen and can you suggest why some quite old code is suddenly causing problems? 
> What is your workload doing that others' do not do?
This is a low probability issue. We conducted monkey testing for a month,
and this problem occurred only once.
The cause of the OOM error is the process surfaceflinger has encountered dma-buf memory leak.

I have not found the root cause of this problem.
The physical memory of the process killed by OOM has been released, indicating that the issue may have occurred due to a concurrency problem
between process termination and OOM kill.
oom kill log：
Out of memory: Killed process 3154 (system_server) total-vm:23662044kB, anon-rss:0kB, file-rss:0kB, shmem-rss:0kB,
UID:1000 pgtables:4056kB oom_score_adj:-900

>> [3701:11_see]user pgtable: 4k pages, 39-bit VAs, pgdp=00000000821de000 
>> [3701:11_see][0000000000000328] pgd=0000000000000000,
>> p4d=0000000000000000,pud=0000000000000000
>> [3701:11_see]tracing off
>> [3701:11_see]Internal error: Oops: 96000005 [#1] PREEMPT SMP 
>> [3701:11_see]Call trace:
>> [3701:11_see] queue_oom_reaper+0x30/0x170 [3701:11_see] 
>> __oom_kill_process+0x590/0x860 [3701:11_see] 
>> oom_kill_process+0x140/0x274 [3701:11_see] out_of_memory+0x2f4/0x54c 
>> [3701:11_see] __alloc_pages_slowpath+0x5d8/0xaac
>> [3701:11_see] __alloc_pages+0x774/0x800 [3701:11_see] 
>> wp_page_copy+0xc4/0x116c [3701:11_see] do_wp_page+0x4bc/0x6fc 
>> [3701:11_see] handle_pte_fault+0x98/0x2a8 [3701:11_see] 
>> __handle_mm_fault+0x368/0x700 [3701:11_see] 
>> do_handle_mm_fault+0x160/0x2cc [3701:11_see] do_page_fault+0x3e0/0x818 
>> [3701:11_see] do_mem_abort+0x68/0x17c [3701:11_see] el0_da+0x3c/0xa0 
>> [3701:11_see] el0t_64_sync_handler+0xc4/0xec [3701:11_see] 
>> el0t_64_sync+0x1b4/0x1b8 [3701:11_see]tracing off
>> 
>> Signed-off-by: Gao Xu <gaoxu2@hihonor.com>

> I'll queue this for -stable backporting, assuming review is agreeable. 
> Can we please identify a suitable Fixes: target to tell -stable maintainers which kernels need the fix?  It looks like this goes back a long way.
The problem occurred on Linux version 5.15.78, There is no difference between the latest kernel version code and Linux version 5.15.78 in the
Function __oom_kill_process, so this problem is likely common to both versions.