Re: [PATCH v2] kasan: Fix lockdep report invalid wait context

From: Vlastimil Babka
Date: Wed Apr 19 2023 - 03:51:37 EST

On 4/19/23 09:26, Marco Elver wrote:
> On Mon, 27 Mar 2023 at 13:48, Zqiang <qiang1.zhang@xxxxxxxxx> wrote:
>>
>> For kernels built with the following options and booting
>>
>> CONFIG_SLUB=y
>> CONFIG_DEBUG_LOCKDEP=y
>> CONFIG_PROVE_LOCKING=y
>> CONFIG_PROVE_RAW_LOCK_NESTING=y
>>
>> [ 0.523115] [ BUG: Invalid wait context ]
>> [ 0.523315] 6.3.0-rc1-yocto-standard+ #739 Not tainted
>> [ 0.523649] -----------------------------
>> [ 0.523663] swapper/0/0 is trying to lock:
>> [ 0.523663] ffff888035611360 (&c->lock){....}-{3:3}, at: put_cpu_partial+0x2e/0x1e0
>> [ 0.523663] other info that might help us debug this:
>> [ 0.523663] context-{2:2}
>> [ 0.523663] no locks held by swapper/0/0.
>> [ 0.523663] stack backtrace:
>> [ 0.523663] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.3.0-rc1-yocto-standard+ #739
>> [ 0.523663] Call Trace:
>> [ 0.523663] <IRQ>
>> [ 0.523663] dump_stack_lvl+0x64/0xb0
>> [ 0.523663] dump_stack+0x10/0x20
>> [ 0.523663] __lock_acquire+0x6c4/0x3c10
>> [ 0.523663] lock_acquire+0x188/0x460
>> [ 0.523663] put_cpu_partial+0x5a/0x1e0
>> [ 0.523663] __slab_free+0x39a/0x520
>> [ 0.523663] ___cache_free+0xa9/0xc0
>> [ 0.523663] qlist_free_all+0x7a/0x160
>> [ 0.523663] per_cpu_remove_cache+0x5c/0x70
>> [ 0.523663] __flush_smp_call_function_queue+0xfc/0x330
>> [ 0.523663] generic_smp_call_function_single_interrupt+0x13/0x20
>> [ 0.523663] __sysvec_call_function+0x86/0x2e0
>> [ 0.523663] sysvec_call_function+0x73/0x90
>> [ 0.523663] </IRQ>
>> [ 0.523663] <TASK>
>> [ 0.523663] asm_sysvec_call_function+0x1b/0x20
>> [ 0.523663] RIP: 0010:default_idle+0x13/0x20
>> [ 0.523663] RSP: 0000:ffffffff83e07dc0 EFLAGS: 00000246
>> [ 0.523663] RAX: 0000000000000000 RBX: ffffffff83e1e200 RCX: ffffffff82a83293
>> [ 0.523663] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff8119a6b1
>> [ 0.523663] RBP: ffffffff83e07dc8 R08: 0000000000000001 R09: ffffed1006ac0d66
>> [ 0.523663] R10: ffff888035606b2b R11: ffffed1006ac0d65 R12: 0000000000000000
>> [ 0.523663] R13: ffffffff83e1e200 R14: ffffffff84a7d980 R15: 0000000000000000
>> [ 0.523663] default_idle_call+0x6c/0xa0
>> [ 0.523663] do_idle+0x2e1/0x330
>> [ 0.523663] cpu_startup_entry+0x20/0x30
>> [ 0.523663] rest_init+0x152/0x240
>> [ 0.523663] arch_call_rest_init+0x13/0x40
>> [ 0.523663] start_kernel+0x331/0x470
>> [ 0.523663] x86_64_start_reservations+0x18/0x40
>> [ 0.523663] x86_64_start_kernel+0xbb/0x120
>> [ 0.523663] secondary_startup_64_no_verify+0xe0/0xeb
>> [ 0.523663] </TASK>
>>
>> The local_lock_irqsave() is invoked in put_cpu_partial() and happens
>> in IPI context, due to the CONFIG_PROVE_RAW_LOCK_NESTING=y (the
>> LD_WAIT_CONFIG not equal to LD_WAIT_SPIN), so acquire local_lock in
>> IPI context will trigger above calltrace.
>>
>> This commit therefore move qlist_free_all() from hard-irq context to
>> task context.
>>
>> Signed-off-by: Zqiang <qiang1.zhang@xxxxxxxxx>
>
> PROVE_RAW_LOCK_NESTING is for the benefit of RT kernels. So it's
> unclear if this is fixing anything on non-RT kernels, besides the
> lockdep warning.

Yes, the problem seems to be that if there's different paths tor RT and !RT
kernels, PROVE_RAW_LOCK_NESTING doesn't know that and will trigger on the
!RT path in the !RT kernel. There's was an annotation proposed for these
cases in the thread linked below, but AFAIK it's not yet finished.

https://lore.kernel.org/all/20230412124735.GE628377@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/

> I'd be inclined to say that having unified code for RT and non-RT
> kernels is better.

Agreed it should be better, as long as it's viable.

> Acked-by: Marco Elver <elver@xxxxxxxxxx>
>
> +Cc RT folks
>
>> ---
>> v1->v2:
>> Modify the commit information and add Cc.
>>
>> mm/kasan/quarantine.c | 34 ++++++++--------------------------
>> 1 file changed, 8 insertions(+), 26 deletions(-)
>>
>> diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c
>> index 75585077eb6d..152dca73f398 100644
>> --- a/mm/kasan/quarantine.c
>> +++ b/mm/kasan/quarantine.c
>> @@ -99,7 +99,6 @@ static unsigned long quarantine_size;
>> static DEFINE_RAW_SPINLOCK(quarantine_lock);
>> DEFINE_STATIC_SRCU(remove_cache_srcu);
>>
>> -#ifdef CONFIG_PREEMPT_RT
>> struct cpu_shrink_qlist {
>> raw_spinlock_t lock;
>> struct qlist_head qlist;
>> @@ -108,7 +107,6 @@ struct cpu_shrink_qlist {
>> static DEFINE_PER_CPU(struct cpu_shrink_qlist, shrink_qlist) = {
>> .lock = __RAW_SPIN_LOCK_UNLOCKED(shrink_qlist.lock),
>> };
>> -#endif
>>
>> /* Maximum size of the global queue. */
>> static unsigned long quarantine_max_size;
>> @@ -319,16 +317,6 @@ static void qlist_move_cache(struct qlist_head *from,
>> }
>> }
>>
>> -#ifndef CONFIG_PREEMPT_RT
>> -static void __per_cpu_remove_cache(struct qlist_head *q, void *arg)
>> -{
>> - struct kmem_cache *cache = arg;
>> - struct qlist_head to_free = QLIST_INIT;
>> -
>> - qlist_move_cache(q, &to_free, cache);
>> - qlist_free_all(&to_free, cache);
>> -}
>> -#else
>> static void __per_cpu_remove_cache(struct qlist_head *q, void *arg)
>> {
>> struct kmem_cache *cache = arg;
>> @@ -340,7 +328,6 @@ static void __per_cpu_remove_cache(struct qlist_head *q, void *arg)
>> qlist_move_cache(q, &sq->qlist, cache);
>> raw_spin_unlock_irqrestore(&sq->lock, flags);
>> }
>> -#endif
>>
>> static void per_cpu_remove_cache(void *arg)
>> {
>> @@ -362,6 +349,8 @@ void kasan_quarantine_remove_cache(struct kmem_cache *cache)
>> {
>> unsigned long flags, i;
>> struct qlist_head to_free = QLIST_INIT;
>> + int cpu;
>> + struct cpu_shrink_qlist *sq;
>>
>> /*
>> * Must be careful to not miss any objects that are being moved from
>> @@ -372,20 +361,13 @@ void kasan_quarantine_remove_cache(struct kmem_cache *cache)
>> */
>> on_each_cpu(per_cpu_remove_cache, cache, 1);
>>
>> -#ifdef CONFIG_PREEMPT_RT
>> - {
>> - int cpu;
>> - struct cpu_shrink_qlist *sq;
>> -
>> - for_each_online_cpu(cpu) {
>> - sq = per_cpu_ptr(&shrink_qlist, cpu);
>> - raw_spin_lock_irqsave(&sq->lock, flags);
>> - qlist_move_cache(&sq->qlist, &to_free, cache);
>> - raw_spin_unlock_irqrestore(&sq->lock, flags);
>> - }
>> - qlist_free_all(&to_free, cache);
>> + for_each_online_cpu(cpu) {
>> + sq = per_cpu_ptr(&shrink_qlist, cpu);
>> + raw_spin_lock_irqsave(&sq->lock, flags);
>> + qlist_move_cache(&sq->qlist, &to_free, cache);
>> + raw_spin_unlock_irqrestore(&sq->lock, flags);
>> }
>> -#endif
>> + qlist_free_all(&to_free, cache);
>>
>> raw_spin_lock_irqsave(&quarantine_lock, flags);
>> for (i = 0; i < QUARANTINE_BATCHES; i++) {
>> --
>> 2.25.1
>>
>> --
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>