On 03/05/2011 06:20 PM, Minchan Kim wrote:
On Sat, Mar 05, 2011 at 02:44:16PM +0300, Andrey Vagin wrote:
Check zone->all_unreclaimable in all_unreclaimable(), otherwise the
kernel may hang up, because shrink_zones() will do nothing, but
all_unreclaimable() will say, that zone has reclaimable pages.
do_try_to_free_pages()
shrink_zones()
for_each_zone
if (zone->all_unreclaimable)
continue
if !all_unreclaimable(zonelist, sc)
return 1
__alloc_pages_slowpath()
retry:
did_some_progress = do_try_to_free_pages(page)
...
if (!page&& did_some_progress)
retry;
Signed-off-by: Andrey Vagin<avagin@xxxxxxxxxx>
---
mm/vmscan.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 6771ea7..1c056f7 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2002,6 +2002,8 @@ static bool all_unreclaimable(struct zonelist *zonelist,
for_each_zone_zonelist_nodemask(zone, z, zonelist,
gfp_zone(sc->gfp_mask), sc->nodemask) {
+ if (zone->all_unreclaimable)
+ continue;
if (!populated_zone(zone))
continue;
if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
zone_reclaimable checks it. Isn't it enough?
I sent one more patch [PATCH] mm: skip zombie in OOM-killer.
This two patches are enough.
Does the hang up really happen or see it by code review?
Yes. You can reproduce it for help the attached python program. It's not
very clever:)
It make the following actions in loop:
1. fork
2. mmap
3. touch memory
4. read memory
5. munmmap
--
1.7.1
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import sys, time, mmap, os
from subprocess import Popen, PIPE
import random
global mem_size
def info(msg):
pid = os.getpid()
print >> sys.stderr, "%s: %s" % (pid, msg)
sys.stderr.flush()
def memory_loop(cmd = "a"):
"""
cmd may be:
c: check memory
else: touch memory
"""
c = 0
for j in xrange(0, mem_size):
if cmd == "c":
if f[j<<12] != chr(j % 255):
info("Data corruption")
sys.exit(1)
else:
f[j<<12] = chr(j % 255)
while True:
pid = os.fork()
if (pid != 0):
mem_size = random.randint(0, 56 * 4096)
f = mmap.mmap(-1, mem_size << 12, mmap.MAP_ANONYMOUS|mmap.MAP_PRIVATE)
memory_loop()
memory_loop("c")
f.close()