On 03/08/2017 06:15 PM, Dmitry Vyukov wrote:
> diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c
> index 6f1ed1630873..075422c3cee3 100644
> --- a/mm/kasan/quarantine.c
> +++ b/mm/kasan/quarantine.c
> @@ -27,6 +27,7 @@
> #include <linux/slab.h>
> #include <linux/string.h>
> #include <linux/types.h>
> +#include <linux/srcu.h>
>
Nit: keep alphabetical order please.
>
> void quarantine_reduce(void)
> {
> size_t total_size, new_quarantine_size, percpu_quarantines;
> unsigned long flags;
> + int srcu_idx;
> struct qlist_head to_free = QLIST_INIT;
>
> if (likely(READ_ONCE(quarantine_size) <=
> READ_ONCE(quarantine_max_size)))
> return;
>
> + /*
> + * srcu critical section ensures that quarantine_remove_cache()
> + * will not miss objects belonging to the cache while they are in our
> + * local to_free list. srcu is chosen because (1) it gives us private
> + * grace period domain that does not interfere with anything else,
> + * and (2) it allows synchronize_srcu() to return without waiting
> + * if there are no pending read critical sections (which is the
> + * expected case).
> + */
> + srcu_idx = srcu_read_lock(&remove_cache_srcu);
I'm puzzled why is SRCU, why not RCU? Given that we take spin_lock in the next line
we certainly don't need ability to sleep in read-side critical section.
> spin_lock_irqsave(&quarantine_lock, flags);
>
> /*
> @@ -237,6 +257,7 @@ void quarantine_reduce(void)
> spin_unlock_irqrestore(&quarantine_lock, flags);
>
> qlist_free_all(&to_free, NULL);
> + srcu_read_unlock(&remove_cache_srcu, srcu_idx);
> }
>
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