linux-kernel - Re: [PATCH] rcu: avoid alloc_pages() when recording stack

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Message-ID: <baa768a3-aacf-ba3a-8d20-0abc78eca2f7@windriver.com>
Date:   Wed, 3 Nov 2021 14:50:49 +0800
From:   Jun Miao <jun.miao@...driver.com>
To:     "Paul E. McKenney" <paulmck@...nel.org>
Cc:     Uladzislau Rezki <urezki@...il.com>,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Dmitry Vyukov <dvyukov@...gle.com>, qiang.zhang1211@...il.com,
        RCU <rcu@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        miaojun0823@....com, ryabinin.a.a@...il.com,
        Alexander Potapenko <glider@...gle.com>,
        jianwei.hu@...driver.com
Subject: Re: [PATCH] rcu: avoid alloc_pages() when recording stack


On 11/2/21 10:53 PM, Uladzislau Rezki wrote:
> [Please note: This e-mail is from an EXTERNAL e-mail address]
>
>> Add KASAN maintainers
>>
>> On 11/1/21 6:31 PM, Jun Miao wrote:
>>> The default kasan_record_aux_stack() calls stack_depot_save() with GFP_NOWAIT,
>>> which in turn can then call alloc_pages(GFP_NOWAIT, ...).  In general, however,
>>> it is not even possible to use either GFP_ATOMIC nor GFP_NOWAIT in certain
>>> non-preemptive contexts/RT kernel including raw_spin_locks (see gfp.h and ab00db216c9c7).
>>>
>>> Fix it by instructing stackdepot to not expand stack storage via alloc_pages()
>>> in case it runs out by using kasan_record_aux_stack_noalloc().
>>>
>>> Jianwei Hu reported:
>>>    BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:969
>>>    in_atomic(): 0, irqs_disabled(): 1, non_block: 0, pid: 15319, name: python3
>>>    INFO: lockdep is turned off.
>>>    irq event stamp: 0
>>>    hardirqs last  enabled at (0): [<0000000000000000>] 0x0
>>>    hardirqs last disabled at (0): [<ffffffff856c8b13>] copy_process+0xaf3/0x2590
>>>    softirqs last  enabled at (0): [<ffffffff856c8b13>] copy_process+0xaf3/0x2590
>>>    softirqs last disabled at (0): [<0000000000000000>] 0x0
>>>    CPU: 6 PID: 15319 Comm: python3 Tainted: G        W  O 5.15-rc7-preempt-rt #1
>>>    Hardware name: Supermicro SYS-E300-9A-8C/A2SDi-8C-HLN4F, BIOS 1.1b 12/17/2018
>>>    Call Trace:
>>>     show_stack+0x52/0x58
>>>     dump_stack+0xa1/0xd6
>>>     ___might_sleep.cold+0x11c/0x12d
>>>     rt_spin_lock+0x3f/0xc0
>>>     rmqueue+0x100/0x1460
>>>     rmqueue+0x100/0x1460
>>>     mark_usage+0x1a0/0x1a0
>>>     ftrace_graph_ret_addr+0x2a/0xb0
>>>     rmqueue_pcplist.constprop.0+0x6a0/0x6a0
>>>      __kasan_check_read+0x11/0x20
>>>      __zone_watermark_ok+0x114/0x270
>>>      get_page_from_freelist+0x148/0x630
>>>      is_module_text_address+0x32/0xa0
>>>      __alloc_pages_nodemask+0x2f6/0x790
>>>      __alloc_pages_slowpath.constprop.0+0x12d0/0x12d0
>>>      create_prof_cpu_mask+0x30/0x30
>>>      alloc_pages_current+0xb1/0x150
>>>      stack_depot_save+0x39f/0x490
>>>      kasan_save_stack+0x42/0x50
>>>      kasan_save_stack+0x23/0x50
>>>      kasan_record_aux_stack+0xa9/0xc0
>>>      __call_rcu+0xff/0x9c0
>>>      call_rcu+0xe/0x10
>>>      put_object+0x53/0x70
>>>      __delete_object+0x7b/0x90
>>>      kmemleak_free+0x46/0x70
>>>      slab_free_freelist_hook+0xb4/0x160
>>>      kfree+0xe5/0x420
>>>      kfree_const+0x17/0x30
>>>      kobject_cleanup+0xaa/0x230
>>>      kobject_put+0x76/0x90
>>>      netdev_queue_update_kobjects+0x17d/0x1f0
>>>      ... ...
>>>      ksys_write+0xd9/0x180
>>>      __x64_sys_write+0x42/0x50
>>>      do_syscall_64+0x38/0x50
>>>      entry_SYSCALL_64_after_hwframe+0x44/0xa9
>>>
>>> Fixes: 84109ab58590 ("rcu: Record kvfree_call_rcu() call stack for KASAN")
>>> Fixes: 26e760c9a7c8 ("rcu: kasan: record and print call_rcu() call stack")
>>> Reported-by: Jianwei Hu <jianwei.hu@...driver.com>
>>> Signed-off-by: Jun Miao <jun.miao@...driver.com>
>>> ---
>>>    kernel/rcu/tree.c | 4 ++--
>>>    1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
>>> index 8270e58cd0f3..2c1034580f15 100644
>>> --- a/kernel/rcu/tree.c
>>> +++ b/kernel/rcu/tree.c
>>> @@ -3026,7 +3026,7 @@ __call_rcu(struct rcu_head *head, rcu_callback_t func)
>>>        head->func = func;
>>>        head->next = NULL;
>>>        local_irq_save(flags);
>>> -     kasan_record_aux_stack(head);
>>> +     kasan_record_aux_stack_noalloc(head);
>>>        rdp = this_cpu_ptr(&rcu_data);
>>>
>>>        /* Add the callback to our list. */
>>> @@ -3591,7 +3591,7 @@ void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
>>>                return;
>>>        }
>>>
>>> -     kasan_record_aux_stack(ptr);
>>> +     kasan_record_aux_stack_noalloc(ptr);
>>>        success = add_ptr_to_bulk_krc_lock(&krcp, &flags, ptr, !head);
>>>        if (!success) {
>>>                run_page_cache_worker(krcp);
> Yep an allocation is tricky here. This change looks correct to me at
> least from the point that it does not allocate.
>
> --
> Uladzislau Rezki

Thanks your approval. Could you like to give me a review?

And This fix patch is my last patch in WindRiver by using email of 
jun.miao@...driver.com. Because i will go to intel next week.

What about your advice @Paul E

---
Jun Miao