Re: [PATCH] slab: initialize unused alien cache entry as NULL atalloc_alien_cache().

From: Haicheng Li
Date: Wed Dec 23 2009 - 06:24:17 EST

Andi Kleen wrote:
Then, this is a violation of the first statement :

nr_node_ids = 1 + nid of highest POSSIBLE node.

If your system allows hotplugging of new nodes, then POSSIBLE nodes should include them
at boot time.

Agreed, nr_node_ids must be possible nodes.

It should have been set up by the SRAT parser (modulo regressions)

Haicheng, did you verify with printk it's really incorrect at this point?

Yup. See below debug patch & Oops info.

If we can make sure that SRAT parser must be able to detect out all possible node (even the node, cpu+mem, is not populated on the motherboard), it would be ACPI Parser issue or BIOS issue rather than a slab issue. In such case, I think this patch might become a workaround for buggy system board; and we might need to look into ACPI SRAT parser code as well:).


---
diff --git a/mm/slab.c b/mm/slab.c
index 7dfa481..3a4e1f4 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1032,6 +1032,9 @@ static void reap_alien(struct kmem_cache *cachep, struct kmem_list3 *l3)
if (l3->alien) {
struct array_cache *ac = l3->alien[node];

+ if (node >= nr_node_ids)
+ printk("node=%d, nr_node_ids=%d, ac=%p\n",
+ node, nr_node_ids, ac);
if (ac && ac->avail && spin_trylock_irq(&ac->lock)) {
__drain_alien_cache(cachep, ac, node);
spin_unlock_irq(&ac->lock);


---
[ 151.732864] node=3, nr_node_ids=2, ac=(null)
[ 151.732873] node=3, nr_node_ids=2, ac=(null)
[ 151.732882] node=3, nr_node_ids=2, ac=(null)
[ 151.732889] node=3, nr_node_ids=2, ac=(null)
[ 151.732897] node=3, nr_node_ids=2, ac=000000004b31f78f
[ 151.732941] BUG: unable to handle kernel paging request at 000000004b31f78f
[ 151.741026] IP: [<ffffffff810bd460>] cache_reap+0x8d/0x252
[ 151.747363] PGD 0
[ 151.749793] Oops: 0000 [#1] SMP
[ 151.753658] last sysfs file: /sys/kernel/kexec_crash_loaded
[ 151.759990] CPU
[ 151.762509] Modules linked in: ipv6 autofs4 rfcomm l2cap crc16 bluetooth rfkill binfmt_misc dm_mirror dm_region_hash dm_log dm_multipath dm_mod video output sbs sbshc fan battery ac parport_pc lp parport joydev usbhid sr_mod cdrom processor thermal thermal_sys container button rtc_cmos rtc_core rtc_lib i2c_i801 i2c_core pcspkr uhci_hcd ohci_hcd ehci_hcd usbcore
[ 151.802035] Pid: 120, comm: events/21 Not tainted 2.6.32-haicheng-cpuhp #34 Server
[ 151.810911] RIP: 0010:[<ffffffff810bd460>] [<ffffffff810bd460>] cache_reap+0x8d/0x252
[ 151.815485] RSP: 0018:ffff88027e81ddf0 EFLAGS: 00010202
[ 151.815491] RAX: 000000000000003d RBX: 000000004b31f78f RCX: 0000000000000000
[ 151.815496] RDX: ffff88027f3f5040 RSI: 0000000000000001 RDI: 0000000000000286
[ 151.815503] RBP: ffff88027e81de30 R08: 0000000000000002 R09: ffffffff8105ee06
[ 151.815507] R10: ffff88027e81dbe0 R11: ffffffff81066722 R12: ffff88047f223080
[ 151.815513] R13: ffff88047dd201c0 R14: 0000000000000003 R15: fffffffff00000c6
[ 151.815518] FS: 0000000000000000(0000) GS:ffff88028b540000(0000) knlGS:0000000000000000
[ 151.815524] CS: 0010 DS: 0018 ES: 0018 CR0: 000000008005003b
[ 151.815528] CR2: 000000004b31f78f CR3: 0000000001001000 CR4: 00000000000006e0
[ 151.815533] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 151.815538] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[ 151.815547] Process events/21 (pid: 120, threadinfo ffff88027e81c000, task ffff88027f3f5040)
[ 151.815550] Stack:
[ 151.817896] ffff88027e81de30 ffff88028b5517c0 0000000100000000 ffff88027e81de80
[ 151.817908] <0> ffff88028b556d80 ffff88028b5517c0 ffffffff810bd3d3 fffffffff00000c6
[ 151.817918] <0> ffff88027e81dec0 ffffffff81058d0c ffffffff81058cb6 ffffffff81376fea
[ 151.817928] Call Trace:
[ 151.820772] [<ffffffff810bd3d3>] ? cache_reap+0x0/0x252
[ 151.820786] [<ffffffff81058d0c>] worker_thread+0x17a/0x27b
[ 151.820793] [<ffffffff81058cb6>] ? worker_thread+0x124/0x27b
[ 151.820806] [<ffffffff81376fea>] ? thread_return+0x3e/0xee
[ 151.820816] [<ffffffff8105bbbc>] ? autoremove_wake_function+0x0/0x38
[ 151.820827] [<ffffffff81058b92>] ? worker_thread+0x0/0x27b
[ 151.820833] [<ffffffff8105babe>] kthread+0x7d/0x87
[ 151.820848] [<ffffffff81012daa>] child_rip+0xa/0x20
[ 151.820857] [<ffffffff81012710>] ? restore_args+0x0/0x30
[ 151.820863] [<ffffffff8105ba41>] ? kthread+0x0/0x87
[ 151.820874] [<ffffffff81012da0>] ? child_rip+0x0/0x20
[ 151.820879] Code: 77 48 63 c6 41 89 f6 48 8b 1c c2 8b 15 be 28 6e 00 39 d6 7c 11 48 89 d9 48 c7 c7 97 98 4c 81 31 c0 e8 23 bf f8 ff 48 85 db 74 4d <83> 3b 00 74 48 48 83 3d 83 ab 66 00 00 75 04 0f 0b eb fe fa 66
[ 151.845235] RIP [<ffffffff810bd460>] cache_reap+0x8d/0x252
[ 151.845255] RSP <ffff88027e81ddf0>
[ 151.845260] CR2: 000000004b31f78f
[ 151.845415] ---[ end trace be6e21fde5d02b06 ]---
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