Messages in this thread Patch in this message | | | Date | Tue, 14 Nov 2017 15:32:00 +0100 | From | Michal Hocko <> | Subject | Re: [PATCH] mm: drop hotplug lock from lru_add_drain_all |
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On Tue 14-11-17 15:23:47, Michal Hocko wrote: [...] > +/* > + * Doesn't need any cpu hotplug locking because we do rely on per-cpu > + * kworkers being shut down before our page_alloc_cpu_dead callback is > + * executed on the offlined cpu > + */ > void lru_add_drain_all(void) > { > static DEFINE_MUTEX(lock);
Ble the part of the comment didn't go through
diff --git a/mm/swap.c b/mm/swap.c index 8bfdcab9f83e..1ab8122d2d0c 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -688,6 +688,13 @@ static void lru_add_drain_per_cpu(struct work_struct *dummy) static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work); +/* + * Doesn't need any cpu hotplug locking because we do rely on per-cpu + * kworkers being shut down before our page_alloc_cpu_dead callback is + * executed on the offlined cpu. + * Calling this function with cpu hotplug locks held can actually lead + * to obscure indirect dependencies via WQ context. + */ void lru_add_drain_all(void) { static DEFINE_MUTEX(lock); -- Michal Hocko SUSE Labs
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