In pageset_set_batch() and setup_pagelist_highmark(), ensure that batch is always set to a safe value (1) prior to updating high, and ensure that high is fully updated before setting the real value of batch. Suggested by Gilad Ben-Yossef <gilad@xxxxxxxxxxxxx> in this thread: https://lkml.org/lkml/2013/4/9/23 Also reproduces his proposed comment. Signed-off-by: Cody P Schafer <cody@xxxxxxxxxxxxxxxxxx> --- mm/page_alloc.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index d259599..a07bd4c 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -4007,11 +4007,26 @@ static int __meminit zone_batchsize(struct zone *zone) #endif } +static void pageset_update_prep(struct per_cpu_pages *pcp) +{ + /* + * We're about to mess with PCP in an non atomic fashion. Put an + * intermediate safe value of batch and make sure it is visible before + * any other change + */ + pcp->batch = 1; + smp_wmb(); +} + /* a companion to setup_pagelist_highmark() */ static void pageset_set_batch(struct per_cpu_pageset *p, unsigned long batch) { struct per_cpu_pages *pcp = &p->pcp; + pageset_update_prep(pcp); + pcp->high = 6 * batch; + smp_wmb(); + pcp->batch = max(1UL, 1 * batch); } @@ -4039,7 +4054,11 @@ static void setup_pagelist_highmark(struct per_cpu_pageset *p, struct per_cpu_pages *pcp; pcp = &p->pcp; + pageset_update_prep(pcp); + pcp->high = high; + smp_wmb(); + pcp->batch = max(1UL, high/4); if ((high/4) > (PAGE_SHIFT * 8)) pcp->batch = PAGE_SHIFT * 8; -- 1.8.2 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>