Re: [PATCH][v2] ipc: prevent lockup on alloc_msg and free_msg
From: Davidlohr Bueso
Date: Tue Mar 12 2019 - 12:47:26 EST
On 2019-03-07 23:12, Li RongQing wrote:
From: Li Rongqing <lirongqing@xxxxxxxxx>
msgctl10 of ltp triggers the following lockup When CONFIG_KASAN
is enabled on large memory SMP systems, the pages initialization
can take a long time, if msgctl10 requests a huge block memory,
and it will block rcu scheduler, so release cpu actively.
After adding schedule() in free_msg, free_msg can not be called
when holding spinlock, so adding msg to a tmp list, and free it
out of spinlock
[79441.630467] rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
[79441.637566] rcu: Tasks blocked on level-1 rcu_node (CPUs 16-31):
P32505
[79441.645355] rcu: Tasks blocked on level-1 rcu_node (CPUs 48-63):
P34978
[79441.653149] rcu: (detected by 11, t=35024 jiffies, g=44237529,
q=16542267)
[79441.661247] msgctl10 R running task 21608 32505 2794
0x00000082
[79441.669455] Call Trace:
[79441.736659] preempt_schedule_irq+0x4c/0xb0
[79441.741578] retint_kernel+0x1b/0x2d
[79441.745796] RIP: 0010:__is_insn_slot_addr+0xfb/0x250
[79441.751595] Code: 82 1d 00 48 8b 9b 90 00 00 00 4c 89 f7 49 c1 ee
03 e8 59 83 1d 00 48 b8 00 00 00 00 00 fc ff df 4c 39 eb 48 89 9d 58
ff ff ff <41> c6 04 06 f8 74 66 4c 8d 75 98 4c 89 f1 48 c1 e9 03 48 01
c8 48
[79441.773232] RSP: 0018:ffff88bce041f758 EFLAGS: 00000246 ORIG_RAX:
ffffffffffffff13
[79441.782071] RAX: dffffc0000000000 RBX: ffffffff8471bc50 RCX:
ffffffff828a2a57
[79441.790337] RDX: dffffc0000000000 RSI: dffffc0000000000 RDI:
ffff88bce041f780
[79441.798612] RBP: ffff88bce041f828 R08: ffffed15f3f4c5b3 R09:
ffffed15f3f4c5b3
[79441.806877] R10: 0000000000000001 R11: ffffed15f3f4c5b2 R12:
000000318aee9b73
[79441.815139] R13: ffffffff8471bc50 R14: 1ffff1179c083ef0 R15:
1ffff1179c083eec
[79441.848618] kernel_text_address+0xc1/0x100
[79441.853542] __kernel_text_address+0xe/0x30
[79441.858453] unwind_get_return_address+0x2f/0x50
[79441.863864] __save_stack_trace+0x92/0x100
[79441.868742] create_object+0x380/0x650
[79441.911831] __kmalloc+0x14c/0x2b0
[79441.915874] load_msg+0x38/0x1a0
[79441.919726] do_msgsnd+0x19e/0xcf0
[79442.006475] do_syscall_64+0x117/0x400
[79442.037964] entry_SYSCALL_64_after_hwframe+0x49/0xbe
[79386.022357] rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
[79386.029455] rcu: Tasks blocked on level-1 rcu_node (CPUs 0-15):
P32170
[79386.037146] rcu: (detected by 14, t=35016 jiffies, g=44237525,
q=12423063)
[79386.045242] msgctl10 R running task 21608 32170 32155
0x00000082
[79386.053447] Call Trace:
[79386.107584] preempt_schedule_irq+0x4c/0xb0
[79386.112495] retint_kernel+0x1b/0x2d
[79386.116712] RIP: 0010:lock_acquire+0x4d/0x340
[79386.121816] Code: 48 81 ec c0 00 00 00 45 89 c6 4d 89 cf 48 8d 6c
24 20 48 89 3c 24 48 8d bb e4 0c 00 00 89 74 24 0c 48 c7 44 24 20 b3
8a b5 41 <48> c1 ed 03 48 c7 44 24 28 b4 25 18 84 48 c7 44 24 30 d0 54
7a 82
[79386.143446] RSP: 0018:ffff88af83417738 EFLAGS: 00000282 ORIG_RAX:
ffffffffffffff13
[79386.152278] RAX: dffffc0000000000 RBX: ffff88bd335f3080 RCX:
0000000000000002
[79386.160543] RDX: 0000000000000000 RSI: 0000000000000000 RDI:
ffff88bd335f3d64
[79386.168798] RBP: ffff88af83417758 R08: 0000000000000000 R09:
0000000000000000
[79386.177049] R10: 0000000000000001 R11: ffffed13f3f745b2 R12:
0000000000000000
[79386.185308] R13: 0000000000000002 R14: 0000000000000000 R15:
0000000000000000
[79386.213791] is_bpf_text_address+0x32/0xe0
[79386.223516] kernel_text_address+0xec/0x100
[79386.233532] __kernel_text_address+0xe/0x30
[79386.238448] unwind_get_return_address+0x2f/0x50
[79386.243858] __save_stack_trace+0x92/0x100
[79386.252648] save_stack+0x32/0xb0
[79386.357923] __kasan_slab_free+0x130/0x180
[79386.362745] kfree+0xfa/0x2d0
[79386.366291] free_msg+0x24/0x50
[79386.370020] do_msgrcv+0x508/0xe60
[79386.446596] do_syscall_64+0x117/0x400
[79386.478122] entry_SYSCALL_64_after_hwframe+0x49/0xbe
Signed-off-by: Li RongQing <lirongqing@xxxxxxxxx>
Signed-off-by: Zhang Yu <zhangyu31@xxxxxxxxx>
---
v1 -->v2: move free_msg out of spinlock in mqueue_evict_inode
move schedule() from loop end to loop start, since it does
not isolate two kmallocs in loop end
ipc/mqueue.c | 10 ++++++++--
ipc/msgutil.c | 6 ++++++
2 files changed, 14 insertions(+), 2 deletions(-)
diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index c0d58f390..bce7af154 100644
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -391,7 +391,8 @@ static void mqueue_evict_inode(struct inode *inode)
struct user_struct *user;
unsigned long mq_bytes, mq_treesize;
struct ipc_namespace *ipc_ns;
- struct msg_msg *msg;
+ struct msg_msg *msg, *nmsg;
+ LIST_HEAD(tmp_msg);
clear_inode(inode);
@@ -402,10 +403,15 @@ static void mqueue_evict_inode(struct inode
*inode)
info = MQUEUE_I(inode);
spin_lock(&info->lock);
while ((msg = msg_get(info)) != NULL)
- free_msg(msg);
+ list_add_tail(&msg->m_list, &tmp_msg);
kfree(info->node_cache);
spin_unlock(&info->lock);
So after releasing the lock, the msg rbtree/list is empty and new calls
will not see those in the newly populated tmp_msg list, and therefore
they cannot access the delayed msg freeing pointers, which is good. Also
the fact that the node_cache is now freed before the actual messages
seems to be harmless as this is wanted for msg_insert() avoiding
GFP_ATOMIC allocations, and after releasing the info->lock the thing is
freed anyway so it should not change things.
Feel free to add my:
Reviewed-by: Davidlohr Bueso <dbueso@xxxxxxx>
+ list_for_each_entry_safe(msg, nmsg, &tmp_msg, m_list) {
+ list_del(&msg->m_list);
+ free_msg(msg);
+ }
+
/* Total amount of bytes accounted for the mqueue */
mq_treesize = info->attr.mq_maxmsg * sizeof(struct msg_msg) +
min_t(unsigned int, info->attr.mq_maxmsg, MQ_PRIO_MAX) *
diff --git a/ipc/msgutil.c b/ipc/msgutil.c
index 84598025a..e65593742 100644
--- a/ipc/msgutil.c
+++ b/ipc/msgutil.c
@@ -18,6 +18,7 @@
#include <linux/utsname.h>
#include <linux/proc_ns.h>
#include <linux/uaccess.h>
+#include <linux/sched.h>
#include "util.h"
@@ -64,6 +65,9 @@ static struct msg_msg *alloc_msg(size_t len)
pseg = &msg->next;
while (len > 0) {
struct msg_msgseg *seg;
+
+ cond_resched();
+
alen = min(len, DATALEN_SEG);
seg = kmalloc(sizeof(*seg) + alen, GFP_KERNEL_ACCOUNT);
if (seg == NULL)
@@ -176,6 +180,8 @@ void free_msg(struct msg_msg *msg)
kfree(msg);
while (seg != NULL) {
struct msg_msgseg *tmp = seg->next;
+
+ cond_resched();
kfree(seg);
seg = tmp;
}