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SubjectRe: [patch V2 1/2] mm: swap: Provide lru_add_drain_all_cpuslocked()
On Tue 04-07-17 11:32:33, 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.

You have added callers in the later patch in the series AFAICS which
is OK but I think it would be better to have them in this patch
already. Nothing earth shattering (maybe a rebase artifact).

> Reported-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Cc: Michal Hocko <mhocko@kernel.org>
> Cc: linux-mm@kvack.org
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Vladimir Davydov <vdavydov.dev@gmail.com>

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
> 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();
> 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
>

--
Michal Hocko
SUSE Labs

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