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Commit 8f9de51a authored by Kirill Korotaev's avatar Kirill Korotaev Committed by Linus Torvalds
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[PATCH] printk() should not be called under zone->lock 



This patch fixes printk() under zone->lock in show_free_areas().  It can be
unsafe to call printk() under this lock, since caller can try to
allocate/free some memory and selfdeadlock on this lock.  I found
allocations/freeing mem both in netconsole and serial console.

This issue was faced in reallity when meminfo was periodically printed for
debug purposes and netconsole was used.

Signed-off-by: default avatarKirill Korotaev <dev@openvz.org>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent d501e62b

mm/page_alloc.c

+5 −4
Original line number Diff line number Diff line
@@ -1491,7 +1491,7 @@ void show_free_areas(void) 
	}



	for_each_zone(zone) {

 		unsigned long nr, flags, order, total = 0;

 		unsigned long nr[MAX_ORDER], flags, order, total = 0;



		show_node(zone);

		printk("%s: ", zone->name);
@@ -1502,11 +1502,12 @@ void show_free_areas(void) 


		spin_lock_irqsave(&zone->lock, flags);

		for (order = 0; order < MAX_ORDER; order++) {

			nr = zone->free_area[order].nr_free;

			total += nr << order;

			printk("%lu*%lukB ", nr, K(1UL) << order);

			nr[order] = zone->free_area[order].nr_free;

			total += nr[order] << order;

		}

		spin_unlock_irqrestore(&zone->lock, flags);

		for (order = 0; order < MAX_ORDER; order++)

			printk("%lu*%lukB ", nr[order], K(1UL) << order);

		printk("= %lukB\n", K(total));

	}