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mem-hotplug: fix potential race while building zonelist for new popul…
…ated zone Add global mutex zonelists_mutex to fix the possible race: CPU0 CPU1 CPU2 (1) zone->present_pages += online_pages; (2) build_all_zonelists(); (3) alloc_page(); (4) free_page(); (5) build_all_zonelists(); (6) __build_all_zonelists(); (7) zone->pageset = alloc_percpu(); In step (3,4), zone->pageset still points to boot_pageset, so bad things may happen if 2+ nodes are in this state. Even if only 1 node is accessing the boot_pageset, (3) may still consume too much memory to fail the memory allocations in step (7). Besides, atomic operation ensures alloc_percpu() in step (7) will never fail since there is a new fresh memory block added in step(6). [[email protected]: hold zonelists_mutex when build_all_zonelists] Signed-off-by: Haicheng Li <[email protected]> Signed-off-by: Wu Fengguang <[email protected]> Reviewed-by: Andi Kleen <[email protected]> Cc: Christoph Lameter <[email protected]> Cc: Mel Gorman <[email protected]> Cc: Tejun Heo <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
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