mm/memory_hotplug: remove broken locking of zone PCP structures during hot remove

zone_pcp_reset allegedly protects against a race with drain_pages using
local_irq_save but this is bogus.  local_irq_save only operates on the
local CPU.  If memory hotplug is running on CPU A and drain_pages is
running on CPU B, disabling IRQs on CPU A does not affect CPU B and
offers no protection.

This patch deletes IRQ disable/enable on the grounds that IRQs protect
nothing and assumes the existing hotplug paths guarantees the PCP cannot
be used after zone_pcp_enable().  That should be the case already
because all the pages have been freed and there is no page to put on the
PCP lists.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Mel Gorman <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Reviewed-by: Oscar Salvador <[email protected]>
Cc: "Michael S. Tsirkin" <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Alexander Duyck <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: David Hildenbrand <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions