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

[Marco Elver]

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.

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

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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