Messages in this thread | | | Date | Sat, 8 Mar 2008 16:56:39 +0100 | From | Mikael Pettersson <> | Subject | 2.6.25 sysdev API problem |
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In kernels up to and including 2.6.24, it was possible to register-then-unregister a sysdev_class/sys_device pair multiple times. Starting with the 2.6.24-git1 kernel, doing so causes a warning
kobject (f88e96c8): tried to init an initialized object, something is seriously wrong
the second time the class/device pair is registered, followed soon thereafter by random BUG()s and a kernel panic.
I'm seeing this problem with an out-of-tree but open-source driver (the "perfctr" performance-monitoring counters driver), but similar sysdev usage patterns can also be found in oprofile and kvm (though I don't use them so I don't know if they have this problem or not).
Below is a simple driver module that illustrates the problem. Inserting it into a 2.6.25-rc4 kernel first causes
foo_sysfs_init foo_sysfs_exit foo_sysfs_init kobject (f88e96c8): tried to init an initialized object, something is seriously wrong Pid: 2078, comm: insmod Not tainted 2.6.25-rc4 #1 [<c01c3926>] kobject_init+0x76/0x80 [<c01c3db3>] kobject_init_and_add+0x13/0x40 [<c02143cf>] sysdev_register+0x5f/0xd0 [<f88e904f>] foo_open_use_close+0x2f/0x80 [foo] [<f88eb00a>] foo_init+0xa/0xd [foo] [<c013ca3c>] sys_init_module+0x11c/0x1ad0 [<c0151210>] handle_mm_fault+0x100/0x5f0 [<c02142b0>] sysdev_unregister+0x0/0x60 [<c0160f9e>] filp_close+0x3e/0x70 [<c0102f2a>] sysenter_past_esp+0x5f/0x85 ======================= foo_sysfs_exit
followed soon thereafter by
------------[ cut here ]------------ Kernel BUG at c015f795 [verbose debug info unavailable] invalid opcode: 0000 [#1] SMP Modules linked in: foo sunrpc af_packet snd_hda_intel snd_seq_oss snd_seq_midi_evee
Pid: 2112, comm: tcsh Not tainted (2.6.25-rc4 #1) EIP: 0060:[<c015f795>] EFLAGS: 00010082 CPU: 1 EIP is at cache_alloc_refill+0x1c5/0x520 EAX: 00000001 EBX: 0000000c ECX: f78046c0 EDX: f7812bc0 ESI: ffffffff EDI: f686d3a0 EBP: f78236c0 ESP: f6a29f34 DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068 Process tcsh (pid: 2112, ti=f6a28000 task=f7b41aa0 task.ti=f6a28000) Stack: 000000d0 000000d0 f7812bc8 f7812bd0 00000000 000000d0 f78046c0 f7817e00 f7812bc0 f71848c0 bfa03b78 00000001 f7169234 f735395c fffffff4 f78046c0 00000282 000000d0 c015f5c2 fffffff4 09815808 b7fc3ff4 f6a28000 c016ab08 Call Trace: [<c015f5c2>] kmem_cache_alloc+0x82/0x90 [<c016ab08>] getname+0x28/0xc0 [<c010137e>] sys_execve+0xe/0x60 [<c0102f2a>] sysenter_past_esp+0x5f/0x85 [<c02a0000>] fn_hash_dump+0xd0/0x240 ======================= Code: 00 83 c4 38 5b 5e 5f 5d c3 8b 7a 10 c7 42 34 01 00 00 00 39 7c 24 0c 74 b8 8 EIP: [<c015f795>] cache_alloc_refill+0x1c5/0x520 SS:ESP 0068:f6a29f34 ---[ end trace aeb1b82666c8fe26 ]---
The BUG() that finally kills the kernel often occurs in cache_alloc_refill(), but it can also occur in other places.
/Mikael
#include <linux/kernel.h> #include <linux/module.h> #include <linux/sysdev.h> #include <linux/version.h>
MODULE_LICENSE("GPL");
static int foo_suspend(struct sys_device *dev, pm_message_t state) { return 0; }
static int foo_resume(struct sys_device *dev) { return 0; }
static struct sysdev_class foo_sysdev_class = { #if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,24) .name = "foo", #else set_kset_name("foo"), #endif .resume = foo_resume, .suspend = foo_suspend, };
static struct sys_device foo_sys_device = { .id = 0, .cls = &foo_sysdev_class, };
static int foo_sysfs_init(void) { int err;
printk("%s\n", __FUNCTION__); err = sysdev_class_register(&foo_sysdev_class); if (!err) err = sysdev_register(&foo_sys_device); if (err) printk("%s failed, err %d\n", __FUNCTION__, err); return err; }
static void foo_sysfs_exit(void) { printk("%s\n", __FUNCTION__); sysdev_unregister(&foo_sys_device); sysdev_class_unregister(&foo_sysdev_class); }
static void foo_open_use_close(void) { if (foo_sysfs_init() == 0) foo_sysfs_exit(); }
int __init foo_init(void) { foo_open_use_close(); foo_open_use_close(); return 0; }
void __exit foo_exit(void) { }
module_init(foo_init) module_exit(foo_exit)
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