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SubjectRe: [PATCH] kasan: convert kasan/quarantine_lock to raw_spinlock
I applied this patch to a fairly stock 4.18-rt5 kernel and booted with no complaints, then
ran rteval for 12h with no stack splats reported. I'll keep banging on it but preliminary
reports look good.

Clark

On Fri, 5 Oct 2018 18:33:20 +0200
Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote:

> On 2018-10-05 18:30:18 [+0200], To Clark Williams wrote:
> > This is the minimum to get this working on RT splat free. There is one
> > memory deallocation with irqs off which should work on RT in its current
> > way.
> > Once this and the on_each_cpu() invocation, I was wondering if…
>
> the patch at the bottom wouldn't work just fine for everyone.
> It would have the beaty of annotating the locking scope a little and
> avoiding the on_each_cpu() invocation. No local_irq_save() but actually
> the proper locking primitives.
> I haven't fully decoded the srcu part in the code.
>
> Wouldn't that work for you?
>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
> mm/kasan/quarantine.c | 45 +++++++++++++++++++++++++------------------
> 1 file changed, 26 insertions(+), 19 deletions(-)
>
> diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c
> index 3a8ddf8baf7dc..8ed595960e3c1 100644
> --- a/mm/kasan/quarantine.c
> +++ b/mm/kasan/quarantine.c
> @@ -39,12 +39,13 @@
> * objects inside of it.
> */
> struct qlist_head {
> + spinlock_t lock;
> struct qlist_node *head;
> struct qlist_node *tail;
> size_t bytes;
> };
>
> -#define QLIST_INIT { NULL, NULL, 0 }
> +#define QLIST_INIT {.head = NULL, .tail = NULL, .bytes = 0 }
>
> static bool qlist_empty(struct qlist_head *q)
> {
> @@ -95,7 +96,9 @@ static void qlist_move_all(struct qlist_head *from, struct qlist_head *to)
> * The object quarantine consists of per-cpu queues and a global queue,
> * guarded by quarantine_lock.
> */
> -static DEFINE_PER_CPU(struct qlist_head, cpu_quarantine);
> +static DEFINE_PER_CPU(struct qlist_head, cpu_quarantine) = {
> + .lock = __SPIN_LOCK_UNLOCKED(cpu_quarantine.lock),
> +};
>
> /* Round-robin FIFO array of batches. */
> static struct qlist_head global_quarantine[QUARANTINE_BATCHES];
> @@ -183,12 +186,13 @@ void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache)
> * beginning which ensures that it either sees the objects in per-cpu
> * lists or in the global quarantine.
> */
> - local_irq_save(flags);
> + q = raw_cpu_ptr(&cpu_quarantine);
> + spin_lock_irqsave(&q->lock, flags);
>
> - q = this_cpu_ptr(&cpu_quarantine);
> qlist_put(q, &info->quarantine_link, cache->size);
> if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) {
> qlist_move_all(q, &temp);
> + spin_unlock(&q->lock);
>
> spin_lock(&quarantine_lock);
> WRITE_ONCE(quarantine_size, quarantine_size + temp.bytes);
> @@ -203,10 +207,10 @@ void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache)
> if (new_tail != quarantine_head)
> quarantine_tail = new_tail;
> }
> - spin_unlock(&quarantine_lock);
> + spin_unlock_irqrestore(&quarantine_lock, flags);
> + } else {
> + spin_unlock_irqrestore(&q->lock, flags);
> }
> -
> - local_irq_restore(flags);
> }
>
> void quarantine_reduce(void)
> @@ -284,21 +288,11 @@ static void qlist_move_cache(struct qlist_head *from,
> }
> }
>
> -static void per_cpu_remove_cache(void *arg)
> -{
> - struct kmem_cache *cache = arg;
> - struct qlist_head to_free = QLIST_INIT;
> - struct qlist_head *q;
> -
> - q = this_cpu_ptr(&cpu_quarantine);
> - qlist_move_cache(q, &to_free, cache);
> - qlist_free_all(&to_free, cache);
> -}
> -
> /* Free all quarantined objects belonging to cache. */
> void quarantine_remove_cache(struct kmem_cache *cache)
> {
> unsigned long flags, i;
> + unsigned int cpu;
> struct qlist_head to_free = QLIST_INIT;
>
> /*
> @@ -308,7 +302,20 @@ void quarantine_remove_cache(struct kmem_cache *cache)
> * achieves the first goal, while synchronize_srcu() achieves the
> * second.
> */
> - on_each_cpu(per_cpu_remove_cache, cache, 1);
> + /* get_online_cpus() invoked by caller */
> + for_each_online_cpu(cpu) {
> + struct qlist_head *q;
> + unsigned long flags;
> + struct qlist_head to_free = QLIST_INIT;
> +
> + q = per_cpu_ptr(&cpu_quarantine, cpu);
> + spin_lock_irqsave(&q->lock, flags);
> + qlist_move_cache(q, &to_free, cache);
> + spin_unlock_irqrestore(&q->lock, flags);
> +
> + qlist_free_all(&to_free, cache);
> +
> + }
>
> spin_lock_irqsave(&quarantine_lock, flags);
> for (i = 0; i < QUARANTINE_BATCHES; i++) {
> --
> 2.19.0
>


--
The United States Coast Guard
Ruining Natural Selection since 1790

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