(9/27/12 2:47 AM), Lai Jiangshan wrote: > The __add_zone() maybe call sleep-able init_currently_empty_zone() > to init wait_table, This doesn't explain why sleepable is critical important. I think sleepable is jsut unrelated. The fact is only: to write zone->zone_start_pfn require zone_span_writelock, but init_currently_empty_zone() doesn't take it. > > But this function also modifies the zone_start_pfn without any lock. > It is bugy. buggy? > So we move this modification out, and we ensure the modification > of zone_start_pfn is only done with zone_span_writelock() held or in booting. > > Since zone_start_pfn is not modified by init_currently_empty_zone() > grow_zone_span() needs to check zone_start_pfn before update it. > > CC: Mel Gorman <mel@xxxxxxxxx> > Signed-off-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxx> > Reported-by: Yasuaki ISIMATU <isimatu.yasuaki@xxxxxxxxxxxxxx> > Tested-by: Wen Congyang <wency@xxxxxxxxxxxxxx> > --- > mm/memory_hotplug.c | 2 +- > mm/page_alloc.c | 3 +-- > 2 files changed, 2 insertions(+), 3 deletions(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index b62d429b..790561f 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -205,7 +205,7 @@ static void grow_zone_span(struct zone *zone, unsigned long start_pfn, > zone_span_writelock(zone); > > old_zone_end_pfn = zone->zone_start_pfn + zone->spanned_pages; > - if (start_pfn < zone->zone_start_pfn) > + if (!zone->zone_start_pfn || start_pfn < zone->zone_start_pfn) > zone->zone_start_pfn = start_pfn; Wrong. zone->zone_start_pfn==0 may be valid pfn. You shouldn't assume it is uninitialized value. > > zone->spanned_pages = max(old_zone_end_pfn, end_pfn) - > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index c13ea75..2545013 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3997,8 +3997,6 @@ int __meminit init_currently_empty_zone(struct zone *zone, > return ret; > pgdat->nr_zones = zone_idx(zone) + 1; > > - zone->zone_start_pfn = zone_start_pfn; > - > mminit_dprintk(MMINIT_TRACE, "memmap_init", > "Initialising map node %d zone %lu pfns %lu -> %lu\n", > pgdat->node_id, > @@ -4465,6 +4463,7 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat, > ret = init_currently_empty_zone(zone, zone_start_pfn, > size, MEMMAP_EARLY); > BUG_ON(ret); > + zone->zone_start_pfn = zone_start_pfn; > memmap_init(size, nid, j, zone_start_pfn); > zone_start_pfn += size; > } > -- 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>