Hi, KOSAKI On 09/28/2012 06:30 AM, KOSAKI Motohiro wrote: > (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. You are right, sleepable is not critical important, but the lock is critical. I am Sorry that I added "sleep-able" and misled guys. Actually I want to say: 1) to write zone->zone_start_pfn require zone_span_writelock 2) init_currently_empty_zone() is sleepable, so we can't use zone_span_writelock() protect the whole init_currently_empty_zone(). 3) so we have to move the modification code out of init_currently_empty_zone() as this patch does. > > >> >> 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. Good catch, I will use zone->spanned_pages instead. Thanks, Lai > > >> >> 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 from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- 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>