On 07/04/2017 11:32 AM, Thomas Gleixner wrote:
> The rework of the cpu hotplug locking unearthed potential deadlocks with
> the memory hotplug locking code.
>
> The solution for these is to rework the memory hotplug locking code as well
> and take the cpu hotplug lock before the memory hotplug lock in
> mem_hotplug_begin(), but this will cause a recursive locking of the cpu
> hotplug lock when the memory hotplug code calls lru_add_drain_all().
>
> Split out the inner workings of lru_add_drain_all() into
> lru_add_drain_all_cpuslocked() so this function can be invoked from the
> memory hotplug code with the cpu hotplug lock held.
>
> Reported-by: Andrey Ryabinin <aryabi...@virtuozzo.com>
> Signed-off-by: Thomas Gleixner <t...@linutronix.de>
> Cc: Michal Hocko <mho...@kernel.org>
> Cc: linux...@kvack.org
> Cc: Andrew Morton <a...@linux-foundation.org>
> Cc: Vlastimil Babka <vba...@suse.cz>
> Cc: Vladimir Davydov <vdavydov....@gmail.com>
Acked-by: Vlastimil Babka <vba...@suse.cz>
A question below.
> ---
> include/linux/swap.h | 1 +
> mm/swap.c | 11 ++++++++---
> 2 files changed, 9 insertions(+), 3 deletions(-)
>
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -277,6 +277,7 @@ extern void mark_page_accessed(struct pa
> extern void lru_add_drain(void);
> extern void lru_add_drain_cpu(int cpu);
> extern void lru_add_drain_all(void);
> +extern void lru_add_drain_all_cpuslocked(void);
> extern void rotate_reclaimable_page(struct page *page);
> extern void deactivate_file_page(struct page *page);
> extern void mark_page_lazyfree(struct page *page);
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -687,7 +687,7 @@ static void lru_add_drain_per_cpu(struct
>
> static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work);
>
> -void lru_add_drain_all(void)
> +void lru_add_drain_all_cpuslocked(void)
> {
> static DEFINE_MUTEX(lock);
> static struct cpumask has_work;
> @@ -701,7 +701,6 @@ void lru_add_drain_all(void)
> return;
>
> mutex_lock(&lock);
> - get_online_cpus();
Is there a an assertion check that we are locked, that could be put in
e.g. VM_WARN_ON_ONCE()?
> cpumask_clear(&has_work);
>
> for_each_online_cpu(cpu) {
> @@ -721,10 +720,16 @@ void lru_add_drain_all(void)
> for_each_cpu(cpu, &has_work)
> flush_work(&per_cpu(lru_add_drain_work, cpu));
>
> - put_online_cpus();
> mutex_unlock(&lock);
> }
>
> +void lru_add_drain_all(void)
> +{
> + get_online_cpus();
> + lru_add_drain_all_cpuslocked();
> + put_online_cpus();
> +}
> +
> /**
> * release_pages - batched put_page()
> * @pages: array of pages to release
>
>
