1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
|
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Wed, 20 Mar 2013 18:06:20 +0100
Subject: net: Add a mutex around devnet_rename_seq
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.2/older/patches-5.2.9-rt3.tar.xz
On RT write_seqcount_begin() disables preemption and device_rename()
allocates memory with GFP_KERNEL and grabs later the sysfs_mutex
mutex. Serialize with a mutex and add use the non preemption disabling
__write_seqcount_begin().
To avoid writer starvation, let the reader grab the mutex and release
it when it detects a writer in progress. This keeps the normal case
(no reader on the fly) fast.
[ tglx: Instead of replacing the seqcount by a mutex, add the mutex ]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
net/core/dev.c | 34 ++++++++++++++++++++--------------
1 file changed, 20 insertions(+), 14 deletions(-)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -195,6 +195,7 @@ static unsigned int napi_gen_id = NR_CPU
static DEFINE_READ_MOSTLY_HASHTABLE(napi_hash, 8);
static seqcount_t devnet_rename_seq;
+static DEFINE_MUTEX(devnet_rename_mutex);
static inline void dev_base_seq_inc(struct net *net)
{
@@ -920,7 +921,8 @@ int netdev_get_name(struct net *net, cha
strcpy(name, dev->name);
rcu_read_unlock();
if (read_seqcount_retry(&devnet_rename_seq, seq)) {
- cond_resched();
+ mutex_lock(&devnet_rename_mutex);
+ mutex_unlock(&devnet_rename_mutex);
goto retry;
}
@@ -1197,20 +1199,17 @@ int dev_change_name(struct net_device *d
likely(!(dev->priv_flags & IFF_LIVE_RENAME_OK)))
return -EBUSY;
- write_seqcount_begin(&devnet_rename_seq);
+ mutex_lock(&devnet_rename_mutex);
+ __raw_write_seqcount_begin(&devnet_rename_seq);
- if (strncmp(newname, dev->name, IFNAMSIZ) == 0) {
- write_seqcount_end(&devnet_rename_seq);
- return 0;
- }
+ if (strncmp(newname, dev->name, IFNAMSIZ) == 0)
+ goto outunlock;
memcpy(oldname, dev->name, IFNAMSIZ);
err = dev_get_valid_name(net, dev, newname);
- if (err < 0) {
- write_seqcount_end(&devnet_rename_seq);
- return err;
- }
+ if (err < 0)
+ goto outunlock;
if (oldname[0] && !strchr(oldname, '%'))
netdev_info(dev, "renamed from %s\n", oldname);
@@ -1223,11 +1222,12 @@ int dev_change_name(struct net_device *d
if (ret) {
memcpy(dev->name, oldname, IFNAMSIZ);
dev->name_assign_type = old_assign_type;
- write_seqcount_end(&devnet_rename_seq);
- return ret;
+ err = ret;
+ goto outunlock;
}
- write_seqcount_end(&devnet_rename_seq);
+ __raw_write_seqcount_end(&devnet_rename_seq);
+ mutex_unlock(&devnet_rename_mutex);
netdev_adjacent_rename_links(dev, oldname);
@@ -1248,7 +1248,8 @@ int dev_change_name(struct net_device *d
/* err >= 0 after dev_alloc_name() or stores the first errno */
if (err >= 0) {
err = ret;
- write_seqcount_begin(&devnet_rename_seq);
+ mutex_lock(&devnet_rename_mutex);
+ __raw_write_seqcount_begin(&devnet_rename_seq);
memcpy(dev->name, oldname, IFNAMSIZ);
memcpy(oldname, newname, IFNAMSIZ);
dev->name_assign_type = old_assign_type;
@@ -1261,6 +1262,11 @@ int dev_change_name(struct net_device *d
}
return err;
+
+outunlock:
+ __raw_write_seqcount_end(&devnet_rename_seq);
+ mutex_unlock(&devnet_rename_mutex);
+ return err;
}
/**
|
