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Message-ID: <6582d31f-e4d5-a982-4797-c22b2dd8b150@bytedance.com>
Date: Tue, 25 Apr 2023 23:51:05 +0800
From: Qi Zheng <zhengqi.arch@...edance.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Vlastimil Babka <vbabka@...e.cz>,
"Zhang, Qiang1" <qiang1.zhang@...el.com>,
Boqun Feng <boqun.feng@...il.com>,
"42.hyeyoo@...il.com" <42.hyeyoo@...il.com>,
"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
"roman.gushchin@...ux.dev" <roman.gushchin@...ux.dev>,
"iamjoonsoo.kim@....com" <iamjoonsoo.kim@....com>,
"rientjes@...gle.com" <rientjes@...gle.com>,
"penberg@...nel.org" <penberg@...nel.org>,
"cl@...ux.com" <cl@...ux.com>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Zhao Gongyi <zhaogongyi@...edance.com>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Thomas Gleixner <tglx@...utronix.de>,
RCU <rcu@...r.kernel.org>,
"Paul E . McKenney" <paulmck@...nel.org>
Subject: Re: [PATCH] mm: slub: annotate kmem_cache_node->list_lock as
raw_spinlock
On 2023/4/25 23:03, Peter Zijlstra wrote:
> On Thu, Apr 13, 2023 at 09:40:13AM +0200, Peter Zijlstra wrote:
>> On Thu, Apr 13, 2023 at 12:44:42AM +0800, Qi Zheng wrote:
>>>> Something like the completely untested below might be of help..
>>
>>> I just tested the above code, and then got the following
>>> warning:
>>>
>>
>>> It seems that the LD_WAIT_SLEEP we set is already greater than the
>>> LD_WAIT_SPIN of the current context.
>>
>> Yeah, I'm an idiot and got it wrong.. I'll try again later if I manage
>> to wake up today :-)
>
> And then I forgot ofcourse :/ Can you give the below (still mostly
> untested) a spin? The crucial difference is the new
> lock_map_acquire_try(). By making the annotation a 'trylock' it will
> skip the acquire of the annotation itself (since trylocks don't block).
Oh, 'trylock' is a good idea. I just tested the following code and
it can resolve the warning I encountered. :)
Thanks,
Qi
>
> ---
> diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
> index 1023f349af71..435a3b0f8ea6 100644
> --- a/include/linux/lockdep.h
> +++ b/include/linux/lockdep.h
> @@ -551,6 +551,7 @@ do { \
> #define rwsem_release(l, i) lock_release(l, i)
>
> #define lock_map_acquire(l) lock_acquire_exclusive(l, 0, 0, NULL, _THIS_IP_)
> +#define lock_map_acquire_try(l) lock_acquire_exclusive(l, 0, 1, NULL, _THIS_IP_)
> #define lock_map_acquire_read(l) lock_acquire_shared_recursive(l, 0, 0, NULL, _THIS_IP_)
> #define lock_map_acquire_tryread(l) lock_acquire_shared_recursive(l, 0, 1, NULL, _THIS_IP_)
> #define lock_map_release(l) lock_release(l, _THIS_IP_)
> diff --git a/include/linux/lockdep_types.h b/include/linux/lockdep_types.h
> index d22430840b53..f3120d6a7d9e 100644
> --- a/include/linux/lockdep_types.h
> +++ b/include/linux/lockdep_types.h
> @@ -33,6 +33,7 @@ enum lockdep_wait_type {
> enum lockdep_lock_type {
> LD_LOCK_NORMAL = 0, /* normal, catch all */
> LD_LOCK_PERCPU, /* percpu */
> + LD_LOCK_WAIT, /* annotation */
> LD_LOCK_MAX,
> };
>
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index 50d4863974e7..d254f9e53c0e 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -2253,6 +2253,9 @@ static inline bool usage_match(struct lock_list *entry, void *mask)
>
> static inline bool usage_skip(struct lock_list *entry, void *mask)
> {
> + if (entry->class->lock_type == LD_LOCK_NORMAL)
> + return false;
> +
> /*
> * Skip local_lock() for irq inversion detection.
> *
> @@ -2279,14 +2282,11 @@ static inline bool usage_skip(struct lock_list *entry, void *mask)
> * As a result, we will skip local_lock(), when we search for irq
> * inversion bugs.
> */
> - if (entry->class->lock_type == LD_LOCK_PERCPU) {
> - if (DEBUG_LOCKS_WARN_ON(entry->class->wait_type_inner < LD_WAIT_CONFIG))
> - return false;
> -
> - return true;
> - }
> + if (entry->class->lock_type == LD_LOCK_PERCPU &&
> + DEBUG_LOCKS_WARN_ON(entry->class->wait_type_inner < LD_WAIT_CONFIG))
> + return false;
>
> - return false;
> + return true;
> }
>
> /*
> @@ -4752,7 +4752,8 @@ static int check_wait_context(struct task_struct *curr, struct held_lock *next)
>
> for (; depth < curr->lockdep_depth; depth++) {
> struct held_lock *prev = curr->held_locks + depth;
> - u8 prev_inner = hlock_class(prev)->wait_type_inner;
> + struct lock_class *class = hlock_class(prev);
> + u8 prev_inner = class->wait_type_inner;
>
> if (prev_inner) {
> /*
> @@ -4762,6 +4763,12 @@ static int check_wait_context(struct task_struct *curr, struct held_lock *next)
> * Also due to trylocks.
> */
> curr_inner = min(curr_inner, prev_inner);
> +
> + /*
> + * Allow override for annotations.
> + */
> + if (unlikely(class->lock_type == LD_LOCK_WAIT))
> + curr_inner = prev_inner;
> }
> }
>
> diff --git a/lib/debugobjects.c b/lib/debugobjects.c
> index df86e649d8be..0e089882146b 100644
> --- a/lib/debugobjects.c
> +++ b/lib/debugobjects.c
> @@ -565,8 +565,16 @@ __debug_object_init(void *addr, const struct debug_obj_descr *descr, int onstack
> * On RT enabled kernels the pool refill must happen in preemptible
> * context:
> */
> - if (!IS_ENABLED(CONFIG_PREEMPT_RT) || preemptible())
> + if (!IS_ENABLED(CONFIG_PREEMPT_RT) || preemptible()) {
> + static struct lockdep_map dep_map = {
> + .name = "wait-type-override",
> + .wait_type_inner = LD_WAIT_SLEEP,
> + .lock_type = LD_LOCK_WAIT,
> + };
> + lock_map_acquire_try(&dep_map);
> fill_pool();
> + lock_map_release(&dep_map);
> + }
>
> db = get_bucket((unsigned long) addr);
>
--
Thanks,
Qi
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