* Tools for checking incorrect usage of locking techniques in k-space
@ 2012-10-27 4:41 Kumar amit mehta
2012-10-27 15:56 ` Srivatsa Bhat
0 siblings, 1 reply; 8+ messages in thread
From: Kumar amit mehta @ 2012-10-27 4:41 UTC (permalink / raw)
To: kernelnewbies
Hi,
I recently came across this tool called KEDR[1] for checking memory leak in
kernel modules. I'm using it to check If my trivial kernel modules (based on
LDD3 examples) are leaking memory. I was wondering if there exist a similar
tool for checking incorrect usage of locking techniques implemented by kernel
module.
-Amit
[1]: http://kedr.berlios.de/
^ permalink raw reply [flat|nested] 8+ messages in thread
* Tools for checking incorrect usage of locking techniques in k-space
2012-10-27 4:41 Tools for checking incorrect usage of locking techniques in k-space Kumar amit mehta
@ 2012-10-27 15:56 ` Srivatsa Bhat
2012-10-27 19:06 ` Kumar amit mehta
0 siblings, 1 reply; 8+ messages in thread
From: Srivatsa Bhat @ 2012-10-27 15:56 UTC (permalink / raw)
To: kernelnewbies
Hi,
On Sat, Oct 27, 2012 at 10:11 AM, Kumar amit mehta <gmate.amit@gmail.com> wrote:
> Hi,
>
> I recently came across this tool called KEDR[1] for checking memory leak in
> kernel modules. I'm using it to check If my trivial kernel modules (based on
> LDD3 examples) are leaking memory. I was wondering if there exist a similar
> tool for checking incorrect usage of locking techniques implemented by kernel
> module.
>
You can make use of the in-kernel "lockdep" framework to check your locking.
Just enable it in your .config, and build and boot your kernel. Lockdep detects
a variety of locking problems at run time and warns you if there is a
possibility
of deadlock etc.
Regards,
Srivatsa S. Bhat
^ permalink raw reply [flat|nested] 8+ messages in thread
* Tools for checking incorrect usage of locking techniques in k-space
2012-10-27 15:56 ` Srivatsa Bhat
@ 2012-10-27 19:06 ` Kumar amit mehta
2012-10-28 18:33 ` Srivatsa Bhat
0 siblings, 1 reply; 8+ messages in thread
From: Kumar amit mehta @ 2012-10-27 19:06 UTC (permalink / raw)
To: kernelnewbies
On Sat, Oct 27, 2012 at 09:26:51PM +0530, Srivatsa Bhat wrote:
> On Sat, Oct 27, 2012 at 10:11 AM, Kumar amit mehta <gmate.amit@gmail.com> wrote:
> > Hi,
> >
> > I recently came across this tool called KEDR[1] for checking memory leak in
> > kernel modules. I'm using it to check If my trivial kernel modules (based on
> > LDD3 examples) are leaking memory. I was wondering if there exist a similar
> > tool for checking incorrect usage of locking techniques implemented by kernel
> > module.
> >
>
> You can make use of the in-kernel "lockdep" framework to check your locking.
> Just enable it in your .config, and build and boot your kernel. Lockdep detects
> a variety of locking problems at run time and warns you if there is a
> possibility
> of deadlock etc.
>
> Regards,
> Srivatsa S. Bhat
Thank you Srivatsa. It seems that lockdep framework is enabled on my running
kernel.
<snip>
amit at ubuntu:/boot$ egrep -i "debug_kernel|lockdep" config-3.2.0-29-generic-pae
CONFIG_LOCKDEP_SUPPORT=y
CONFIG_DEBUG_KERNEL=y
<snip>
If above configuration is all that I need, then should I be seeing warning/error
messages in kernel logs(/var/log/kern.log) when there is inconsistency in
locking ? To test my hypothesis, I modified my simple kernel module to
deliberately induce locking error (After initializing read-write semaphore, I call
down_write() and do not free this semaphore lock by commenting out up_write()
invocation). But still I don't see any error or warning message trace in kernel
logs, I think, I'm missing something. I've just now found out that there is a
tutorial on runtime locking correctness validator[1] under Documentation. I'll
go through it.
On the other hand, I found this KEDR utility very simple and accurate in finding
out the erroneous memory handling. For example, this is how the KEDR reports
memory leakage in my kernel module:
<snip>
2670043 Oct 27 06:32:38 ubuntu kernel: [16963.930621] Inside echo_exit: kfree()
2670044 Oct 27 06:32:38 ubuntu kernel: [16963.930886] [leak_check] LeakCheck has
detected possible memory leaks:
2670045 Oct 27 06:32:38 ubuntu kernel: [16963.930897] [leak_check] Address:
0xeeafbb70, size: 9; stack trace of the allocation:
2670046 Oct 27 06:32:38 ubuntu kernel: [16963.930907] [leak_check] [<f86ac0b2>]
echo_write+0x42/0xd0 [echo]
2670047 Oct 27 06:32:38 ubuntu kernel: [16964.001413] [leak_check] [<c11448bf>]
vfs_write+0x8f/0x160
2670048 Oct 27 06:32:38 ubuntu kernel: [16964.001421] [leak_check] [<c1144b9d>]
sys_write+0x3d/0x70
2670049 Oct 27 06:32:38 ubuntu kernel: [16964.002214] [leak_check] [<c15ac7df>]
sysenter_do_call+0x12/0x28
2670050 Oct 27 06:32:38 ubuntu kernel: [16964.002238] [leak_check] [<ffffffff>]
0xffffffff
2670051 Oct 27 06:32:38 ubuntu kernel: [16964.002242] [leak_check]
----------------------------------------
2670052 Oct 27 06:32:38 ubuntu kernel: [16964.002248] [leak_check] Totals:
2670053 Oct 27 06:32:38 ubuntu kernel: [16964.002251] [leak_check] Allocations:
3
2670054 Oct 27 06:32:38 ubuntu kernel: [16964.002255] [leak_check] Possible
leaks: 1
2670055 Oct 27 06:32:38 ubuntu kernel: [16964.002257] [leak_check] Unallocated
frees: 0
2670056 Oct 27 06:32:38 ubuntu kernel: [16964.002260] [leak_check] ======== end
of LeakCheck report ========
<snip>
As you can see that with reports generated by KEDR like above, it becomes easy
to detect the memory leak and therefore I'm looking at something similar like KEDR
for detecting locking errors in kernel module.
-Amit
[1] http://lxr.linux.no/#linux+v3.6.3/Documentation/lockdep-design.txt
^ permalink raw reply [flat|nested] 8+ messages in thread
* Tools for checking incorrect usage of locking techniques in k-space
2012-10-27 19:06 ` Kumar amit mehta
@ 2012-10-28 18:33 ` Srivatsa Bhat
2012-10-30 5:41 ` Kumar amit mehta
0 siblings, 1 reply; 8+ messages in thread
From: Srivatsa Bhat @ 2012-10-28 18:33 UTC (permalink / raw)
To: kernelnewbies
Hi,
On Sun, Oct 28, 2012 at 12:36 AM, Kumar amit mehta <gmate.amit@gmail.com> wrote:
> Thank you Srivatsa. It seems that lockdep framework is enabled on my running
> kernel.
>
> <snip>
> amit at ubuntu:/boot$ egrep -i "debug_kernel|lockdep" config-3.2.0-29-generic-pae
> CONFIG_LOCKDEP_SUPPORT=y
> CONFIG_DEBUG_KERNEL=y
You'll need CONFIG_LOCKDEP=y as well. An easy way to configure lock debugging
checks is to run 'make menuconfig' and enable the required options under the
"Kernel hacking" section.
Regards,
Srivatsa S. Bhat
> <snip>
>
> If above configuration is all that I need, then should I be seeing warning/error
> messages in kernel logs(/var/log/kern.log) when there is inconsistency in
> locking ? To test my hypothesis, I modified my simple kernel module to
> deliberately induce locking error (After initializing read-write semaphore, I call
> down_write() and do not free this semaphore lock by commenting out up_write()
> invocation). But still I don't see any error or warning message trace in kernel
> logs, I think, I'm missing something.
^ permalink raw reply [flat|nested] 8+ messages in thread
* Tools for checking incorrect usage of locking techniques in k-space
2012-10-28 18:33 ` Srivatsa Bhat
@ 2012-10-30 5:41 ` Kumar amit mehta
2012-11-05 5:51 ` Vladimir Murzin
0 siblings, 1 reply; 8+ messages in thread
From: Kumar amit mehta @ 2012-10-30 5:41 UTC (permalink / raw)
To: kernelnewbies
On Mon, Oct 29, 2012 at 12:03:08AM +0530, Srivatsa Bhat wrote:
> You'll need CONFIG_LOCKDEP=y as well. An easy way to configure lock debugging
> checks is to run 'make menuconfig' and enable the required options under the
> "Kernel hacking" section.
>
> >
> > If above configuration is all that I need, then should I be seeing warning/error
> > messages in kernel logs(/var/log/kern.log) when there is inconsistency in
> > locking ? To test my hypothesis, I modified my simple kernel module to
> > deliberately induce locking error (After initializing read-write semaphore, I call
> > down_write() and do not free this semaphore lock by commenting out up_write()
> > invocation). But still I don't see any error or warning message trace in kernel
> > logs, I think, I'm missing something.
Hi Srivatsa,
Thank you for your mail. As per your suggestion, this time I've enabled
CONFIG_LOCKDEP aslo in my running kernel and did the same experiment, but still
I dont't see any warning/error messages in the kernel log. To give you more idea
about what I'm doing, Please see the code below.(This is a simple char driver
based on LDD3 examples)
<echo.c>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/types.h> //MAJOR, MINOR
#include <linux/fs.h> //register_chrdev_region, file_operations
#include <linux/moduleparam.h>
#include <linux/kernel.h> //container_of
#include <linux/slab.h> //kmalloc
#include <linux/cdev.h> //struct cdev
#include <linux/version.h>
#include <linux/uaccess.h> //copy_from/to_user()
#include <linux/errno.h> //error code
ssize_t echo_read(struct file *, char __user *, size_t, loff_t *);
ssize_t echo_write(struct file *, const char __user *, size_t, loff_t *);
int echo_open(struct inode *, struct file *);
int echo_release(struct inode *, struct file *);
struct echo_cdev {
char *data;
unsigned long size; //amount of data stored
struct semaphore sem;
struct cdev cdev;
};
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("amit");
int nr_major;
module_param(nr_major, int, S_IRUGO);
MODULE_PARM_DESC(nr_major, "major number");
int nr_minor;
char *chrdev_name = "echo";
static dev_t device;
static int echo_dev_count = 1;
struct echo_cdev *echo_dev = NULL;
static struct file_operations echo_fs_ops = {
.open = echo_open,
.release = echo_release,
.read = echo_read,
.write = echo_write,
.owner = THIS_MODULE,
};
int echo_open(struct inode *inode, struct file *filp)
{
struct echo_cdev *dev;
pr_debug("%s: f_flags: 0x%x\n",__FUNCTION__,filp->f_flags);
//container_of(pointer, container_type, container_field);
dev = container_of(inode->i_cdev, struct echo_cdev, cdev);
filp->private_data = dev;
if ((filp->f_flags & O_ACCMODE) == O_WRONLY) {
//trim the device size to 0
dev->size = 0;
}
return 0;
}
int echo_release(struct inode *inode, struct file *filp)
{
return 0;
}
ssize_t echo_read(struct file *filp, char __user *ubuff, size_t count, loff_t *poffset)
{
struct echo_cdev *dev = filp->private_data;
pr_debug("%s: f_flags: 0x%x\n",__FUNCTION__,filp->f_flags);
//user trying to access an offset which is beyond the end of file
if (down_interruptible(&dev->sem))
return -ERESTARTSYS;
if (*poffset >= dev->size) {
up(&dev->sem);
return 0;
}
//user trying to access more than eof, return bytes read till the eof
if (*poffset + count >= dev->size)
//count = dev->size - *poffset;
count = dev->size;
//kspace --> uspace
if (copy_to_user(ubuff, (dev->data + *poffset), count) < 0) {
up(&dev->sem);
return -EFAULT;
}
//update the offset
*poffset += count;
up(&dev->sem);
return count;
}
//count is the size of requested data transfer
ssize_t echo_write(struct file *filp, const char __user *ubuff, size_t count, loff_t *poffset)
{
int ret;
struct echo_cdev *dev = filp->private_data;
pr_debug("%s: f_flags: 0x%x\n",__FUNCTION__,filp->f_flags);
if (down_interruptible(&dev->sem))
return -ERESTARTSYS;
if (dev->data == NULL) {
dev->data = (char *)kmalloc(count, GFP_KERNEL);
if (!dev->data) {
up(&dev->sem);
return -ENOMEM;
} else {
memset(dev->data, 0, sizeof(count));
}
}
dev->size = count;
//uspace --> kspace
if (copy_from_user(dev->data, ubuff, count) < 0) {
up(&dev->sem);
return -EFAULT;
}
*poffset += count;
ret = count;
if (dev->size < *poffset)
dev->size = *poffset;
//Force lock error
//up(&dev->sem);
return ret;
}
static int __init echo_init(void)
{
int ret;
printk(KERN_EMERG "entering %s\n",__FUNCTION__);
//let the user provide the major number.
if (nr_major) {
device = MKDEV(nr_major, nr_minor);
if ((ret = register_chrdev_region(device, echo_dev_count, chrdev_name)) < 0) {
pr_debug("%s: failed to register %s\n",__FUNCTION__,
chrdev_name);
return ret;
}
} else {
ret = alloc_chrdev_region(&device, 0, echo_dev_count, chrdev_name);
if (ret < 0) {
pr_debug("%s: failed to register %s\n",__FUNCTION__,
chrdev_name);
return ret;
}
}
nr_major = MAJOR(device);
nr_minor = MINOR(device);
//print the major and minor numbers
pr_debug("%s: major/minor:: %d/%d\n",__FUNCTION__,
nr_major, nr_minor);
echo_dev = (struct echo_cdev *)kmalloc(sizeof(struct echo_cdev), GFP_KERNEL);
if (!echo_dev) {
printk(KERN_EMERG "Not enough memory\n");
unregister_chrdev_region(device, echo_dev_count);
return -ENOMEM;
}
memset(echo_dev, 0, sizeof(struct echo_cdev));
echo_dev->cdev.owner = THIS_MODULE;
echo_dev->cdev.ops = &echo_fs_ops;
//initialize the semaphore, before it is presented to the world
sema_init(&echo_dev->sem,1);
cdev_init(&echo_dev->cdev, &echo_fs_ops);
device = MKDEV(nr_major, nr_minor);
//tell the kernel about this char device
//telling the VFS layer to associate echo driver's fs operation for file r/w etc.
ret = cdev_add(&echo_dev->cdev, device, 1);
if (ret) {
kfree(echo_dev);
unregister_chrdev_region(device, echo_dev_count);
return ret;
}
return 0;
}
static void __exit echo_exit(void)
{
printk(KERN_EMERG "entering %s\n",__FUNCTION__);
if (echo_dev->data) {
printk("Inside %s: kfree()\n",__FUNCTION__);
kfree(echo_dev->data);
}
cdev_del(&echo_dev->cdev);
kfree(echo_dev);
unregister_chrdev_region(device, echo_dev_count);
}
module_init(echo_init);
module_exit(echo_exit);
<echo.c>
<Makefile>
obj-m := echo.o
CFLAGS_echo.o := -DDEBUG -Wall -Werror -Wmissing-prototypes \
-Wstrict-prototypes -Wunused-variable -O2 \
-Wunused-function -g
modules:
make -C /lib/modules/`uname -r`/build M=`pwd`
clean:
make -C /lib/modules/`uname -r`/build M=`pwd` clean
<Makefile>
Logs:
root at ubuntu:/boot# egrep -i "debug_kernel|lockdep"
config-3.7.0-rc3-next-20121029
CONFIG_LOCKDEP_SUPPORT=y
CONFIG_DEBUG_KERNEL=y
CONFIG_LOCKDEP=y
# CONFIG_DEBUG_LOCKDEP is not set
root at ubuntu:/home/amit/ldd3/misc-modules/echo# uname -a
Linux ubuntu 3.7.0-rc3-next-20121029 #1 SMP Mon Oct 29 21:42:20 PDT 2012 i686
i686 i386 GNU/Linux
root at ubuntu:/home/amit/ldd3/misc-modules/echo# dmesg
root at ubuntu:/home/amit/ldd3/misc-modules/echo# insmod echo.ko
root at ubuntu:/home/amit/ldd3/misc-modules/echo# dmesg
[ 1156.704072] entering echo_init
[ 1156.704914] echo_init: major/minor:: 249/0
root at ubuntu:/home/amit/ldd3/misc-modules/echo# mknod /dev/echo c 249 0
root at ubuntu:/home/amit/ldd3/misc-modules/echo# ll /dev/echo
crw-r--r-- 1 root root 249, 0 Oct 29 22:29 /dev/echo
root at ubuntu:/home/amit/ldd3/misc-modules/echo# echo "kernel newbiee" >/dev/echo
root at ubuntu:/home/amit/ldd3/misc-modules/echo# dmesg
[ 1156.704072] entering echo_init
[ 1156.704914] echo_init: major/minor:: 249/0
[ 1237.377205] echo_open: f_flags: 0x8241
[ 1237.377392] echo_write: f_flags: 0x8001
root at ubuntu:/home/amit/ldd3/misc-modules/echo# cat /dev/echo
--> Here the driver read routine gets stuck as I've not reliquished the
semaphore lock
root at ubuntu:/home/amit/ldd3/misc-modules/echo# cat /dev/echo
^C <-- killing the user process
root at ubuntu:/home/amit/ldd3/misc-modules/echo# rmmod echo
root@ubuntu:/home/amit/ldd3/misc-modules/echo# dmesg
[ 1156.704072] entering echo_init
[ 1156.704914] echo_init: major/minor:: 249/0
[ 1237.377205] echo_open: f_flags: 0x8241
[ 1237.377392] echo_write: f_flags: 0x8001
[ 1270.622337] echo_open: f_flags: 0x8000
[ 1270.622477] echo_read: f_flags: 0x8000
[ 1394.180962] entering echo_exit
[ 1394.180996] Inside echo_exit: kfree()
As you can see, no warning/error messages reported by kernel.
-Amit
^ permalink raw reply [flat|nested] 8+ messages in thread
* Tools for checking incorrect usage of locking techniques in k-space
2012-10-30 5:41 ` Kumar amit mehta
@ 2012-11-05 5:51 ` Vladimir Murzin
2012-11-05 7:24 ` Anand Moon
2012-11-06 9:30 ` Kumar amit mehta
0 siblings, 2 replies; 8+ messages in thread
From: Vladimir Murzin @ 2012-11-05 5:51 UTC (permalink / raw)
To: kernelnewbies
On Tue, Oct 30, 2012 at 9:41 AM, Kumar amit mehta <gmate.amit@gmail.com> wrote:
> On Mon, Oct 29, 2012 at 12:03:08AM +0530, Srivatsa Bhat wrote:
>> You'll need CONFIG_LOCKDEP=y as well. An easy way to configure lock debugging
>> checks is to run 'make menuconfig' and enable the required options under the
>> "Kernel hacking" section.
>>
>> >
>> > If above configuration is all that I need, then should I be seeing warning/error
>> > messages in kernel logs(/var/log/kern.log) when there is inconsistency in
>> > locking ? To test my hypothesis, I modified my simple kernel module to
>> > deliberately induce locking error (After initializing read-write semaphore, I call
>> > down_write() and do not free this semaphore lock by commenting out up_write()
>> > invocation). But still I don't see any error or warning message trace in kernel
>> > logs, I think, I'm missing something.
>
> Hi Srivatsa,
>
> Thank you for your mail. As per your suggestion, this time I've enabled
> CONFIG_LOCKDEP aslo in my running kernel and did the same experiment, but still
> I dont't see any warning/error messages in the kernel log. To give you more idea
> about what I'm doing, Please see the code below.(This is a simple char driver
> based on LDD3 examples)
>
> <echo.c>
>
> #include <linux/module.h>
> #include <linux/init.h>
> #include <linux/types.h> //MAJOR, MINOR
> #include <linux/fs.h> //register_chrdev_region, file_operations
> #include <linux/moduleparam.h>
> #include <linux/kernel.h> //container_of
> #include <linux/slab.h> //kmalloc
> #include <linux/cdev.h> //struct cdev
> #include <linux/version.h>
> #include <linux/uaccess.h> //copy_from/to_user()
> #include <linux/errno.h> //error code
>
> ssize_t echo_read(struct file *, char __user *, size_t, loff_t *);
> ssize_t echo_write(struct file *, const char __user *, size_t, loff_t *);
> int echo_open(struct inode *, struct file *);
> int echo_release(struct inode *, struct file *);
>
> struct echo_cdev {
> char *data;
> unsigned long size; //amount of data stored
> struct semaphore sem;
> struct cdev cdev;
> };
> MODULE_LICENSE("GPL v2");
> MODULE_AUTHOR("amit");
>
> int nr_major;
> module_param(nr_major, int, S_IRUGO);
> MODULE_PARM_DESC(nr_major, "major number");
>
> int nr_minor;
> char *chrdev_name = "echo";
>
> static dev_t device;
> static int echo_dev_count = 1;
> struct echo_cdev *echo_dev = NULL;
>
> static struct file_operations echo_fs_ops = {
> .open = echo_open,
> .release = echo_release,
> .read = echo_read,
> .write = echo_write,
> .owner = THIS_MODULE,
> };
>
> int echo_open(struct inode *inode, struct file *filp)
> {
> struct echo_cdev *dev;
> pr_debug("%s: f_flags: 0x%x\n",__FUNCTION__,filp->f_flags);
> //container_of(pointer, container_type, container_field);
> dev = container_of(inode->i_cdev, struct echo_cdev, cdev);
> filp->private_data = dev;
> if ((filp->f_flags & O_ACCMODE) == O_WRONLY) {
> //trim the device size to 0
> dev->size = 0;
> }
> return 0;
> }
>
> int echo_release(struct inode *inode, struct file *filp)
> {
> return 0;
> }
>
> ssize_t echo_read(struct file *filp, char __user *ubuff, size_t count, loff_t *poffset)
> {
> struct echo_cdev *dev = filp->private_data;
> pr_debug("%s: f_flags: 0x%x\n",__FUNCTION__,filp->f_flags);
>
> //user trying to access an offset which is beyond the end of file
> if (down_interruptible(&dev->sem))
> return -ERESTARTSYS;
> if (*poffset >= dev->size) {
> up(&dev->sem);
> return 0;
> }
>
> //user trying to access more than eof, return bytes read till the eof
> if (*poffset + count >= dev->size)
> //count = dev->size - *poffset;
> count = dev->size;
> //kspace --> uspace
> if (copy_to_user(ubuff, (dev->data + *poffset), count) < 0) {
> up(&dev->sem);
> return -EFAULT;
> }
> //update the offset
> *poffset += count;
> up(&dev->sem);
> return count;
> }
>
> //count is the size of requested data transfer
> ssize_t echo_write(struct file *filp, const char __user *ubuff, size_t count, loff_t *poffset)
> {
> int ret;
> struct echo_cdev *dev = filp->private_data;
> pr_debug("%s: f_flags: 0x%x\n",__FUNCTION__,filp->f_flags);
> if (down_interruptible(&dev->sem))
> return -ERESTARTSYS;
> if (dev->data == NULL) {
> dev->data = (char *)kmalloc(count, GFP_KERNEL);
> if (!dev->data) {
> up(&dev->sem);
> return -ENOMEM;
> } else {
> memset(dev->data, 0, sizeof(count));
> }
> }
> dev->size = count;
> //uspace --> kspace
> if (copy_from_user(dev->data, ubuff, count) < 0) {
> up(&dev->sem);
> return -EFAULT;
> }
>
> *poffset += count;
> ret = count;
>
> if (dev->size < *poffset)
> dev->size = *poffset;
> //Force lock error
> //up(&dev->sem);
> return ret;
> }
>
> static int __init echo_init(void)
> {
> int ret;
> printk(KERN_EMERG "entering %s\n",__FUNCTION__);
> //let the user provide the major number.
> if (nr_major) {
> device = MKDEV(nr_major, nr_minor);
> if ((ret = register_chrdev_region(device, echo_dev_count, chrdev_name)) < 0) {
> pr_debug("%s: failed to register %s\n",__FUNCTION__,
> chrdev_name);
> return ret;
> }
> } else {
> ret = alloc_chrdev_region(&device, 0, echo_dev_count, chrdev_name);
> if (ret < 0) {
> pr_debug("%s: failed to register %s\n",__FUNCTION__,
> chrdev_name);
> return ret;
> }
> }
> nr_major = MAJOR(device);
> nr_minor = MINOR(device);
> //print the major and minor numbers
> pr_debug("%s: major/minor:: %d/%d\n",__FUNCTION__,
> nr_major, nr_minor);
> echo_dev = (struct echo_cdev *)kmalloc(sizeof(struct echo_cdev), GFP_KERNEL);
> if (!echo_dev) {
> printk(KERN_EMERG "Not enough memory\n");
> unregister_chrdev_region(device, echo_dev_count);
> return -ENOMEM;
> }
> memset(echo_dev, 0, sizeof(struct echo_cdev));
> echo_dev->cdev.owner = THIS_MODULE;
> echo_dev->cdev.ops = &echo_fs_ops;
> //initialize the semaphore, before it is presented to the world
> sema_init(&echo_dev->sem,1);
> cdev_init(&echo_dev->cdev, &echo_fs_ops);
> device = MKDEV(nr_major, nr_minor);
> //tell the kernel about this char device
> //telling the VFS layer to associate echo driver's fs operation for file r/w etc.
> ret = cdev_add(&echo_dev->cdev, device, 1);
> if (ret) {
> kfree(echo_dev);
> unregister_chrdev_region(device, echo_dev_count);
> return ret;
> }
> return 0;
> }
>
> static void __exit echo_exit(void)
> {
> printk(KERN_EMERG "entering %s\n",__FUNCTION__);
> if (echo_dev->data) {
> printk("Inside %s: kfree()\n",__FUNCTION__);
> kfree(echo_dev->data);
> }
> cdev_del(&echo_dev->cdev);
> kfree(echo_dev);
> unregister_chrdev_region(device, echo_dev_count);
> }
>
> module_init(echo_init);
> module_exit(echo_exit);
>
> <echo.c>
>
> <Makefile>
> obj-m := echo.o
> CFLAGS_echo.o := -DDEBUG -Wall -Werror -Wmissing-prototypes \
> -Wstrict-prototypes -Wunused-variable -O2 \
> -Wunused-function -g
>
> modules:
> make -C /lib/modules/`uname -r`/build M=`pwd`
> clean:
> make -C /lib/modules/`uname -r`/build M=`pwd` clean
> <Makefile>
>
> Logs:
> root at ubuntu:/boot# egrep -i "debug_kernel|lockdep"
> config-3.7.0-rc3-next-20121029
> CONFIG_LOCKDEP_SUPPORT=y
> CONFIG_DEBUG_KERNEL=y
> CONFIG_LOCKDEP=y
> # CONFIG_DEBUG_LOCKDEP is not set
>
> root at ubuntu:/home/amit/ldd3/misc-modules/echo# uname -a
> Linux ubuntu 3.7.0-rc3-next-20121029 #1 SMP Mon Oct 29 21:42:20 PDT 2012 i686
> i686 i386 GNU/Linux
>
> root at ubuntu:/home/amit/ldd3/misc-modules/echo# dmesg
>
> root at ubuntu:/home/amit/ldd3/misc-modules/echo# insmod echo.ko
>
> root at ubuntu:/home/amit/ldd3/misc-modules/echo# dmesg
> [ 1156.704072] entering echo_init
> [ 1156.704914] echo_init: major/minor:: 249/0
>
> root at ubuntu:/home/amit/ldd3/misc-modules/echo# mknod /dev/echo c 249 0
>
> root at ubuntu:/home/amit/ldd3/misc-modules/echo# ll /dev/echo
> crw-r--r-- 1 root root 249, 0 Oct 29 22:29 /dev/echo
>
> root at ubuntu:/home/amit/ldd3/misc-modules/echo# echo "kernel newbiee" >/dev/echo
>
> root at ubuntu:/home/amit/ldd3/misc-modules/echo# dmesg
> [ 1156.704072] entering echo_init
> [ 1156.704914] echo_init: major/minor:: 249/0
> [ 1237.377205] echo_open: f_flags: 0x8241
> [ 1237.377392] echo_write: f_flags: 0x8001
>
> root at ubuntu:/home/amit/ldd3/misc-modules/echo# cat /dev/echo
> --> Here the driver read routine gets stuck as I've not reliquished the
> semaphore lock
>
> root at ubuntu:/home/amit/ldd3/misc-modules/echo# cat /dev/echo
> ^C <-- killing the user process
>
> root at ubuntu:/home/amit/ldd3/misc-modules/echo# rmmod echo
>
> root at ubuntu:/home/amit/ldd3/misc-modules/echo# dmesg
> [ 1156.704072] entering echo_init
> [ 1156.704914] echo_init: major/minor:: 249/0
> [ 1237.377205] echo_open: f_flags: 0x8241
> [ 1237.377392] echo_write: f_flags: 0x8001
> [ 1270.622337] echo_open: f_flags: 0x8000
> [ 1270.622477] echo_read: f_flags: 0x8000
> [ 1394.180962] entering echo_exit
> [ 1394.180996] Inside echo_exit: kfree()
>
> As you can see, no warning/error messages reported by kernel.
> -Amit
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Hi
I've not tried your module, but I suppose that you should get warning
as soon as you try to take write semaphore once again.
Best wishes
Vladimir Murzin
^ permalink raw reply [flat|nested] 8+ messages in thread
* Tools for checking incorrect usage of locking techniques in k-space
2012-11-05 5:51 ` Vladimir Murzin
@ 2012-11-05 7:24 ` Anand Moon
2012-11-06 9:30 ` Kumar amit mehta
1 sibling, 0 replies; 8+ messages in thread
From: Anand Moon @ 2012-11-05 7:24 UTC (permalink / raw)
To: kernelnewbies
?
Hi All,
?
While building the new kernel their are many option for kernel debugging
?
please refer the below link.
?
http://my.safaribooksonline.com/book/operating-systems-and-server-administration/linux/9780137072446/kernel-hacking-config-options/ch11
?
Hope this will help you catch the lock problem.
?
-Anand Moon
________________________________
From: Vladimir Murzin <murzin.v@gmail.com>
To: Kumar amit mehta <gmate.amit@gmail.com>
Cc: Srivatsa Bhat <bhat.srivatsa@gmail.com>; kernelnewbies at kernelnewbies.org
Sent: Monday, November 5, 2012 11:21 AM
Subject: Re: Tools for checking incorrect usage of locking techniques in k-space
On Tue, Oct 30, 2012 at 9:41 AM, Kumar amit mehta <gmate.amit@gmail.com> wrote:
> On Mon, Oct 29, 2012 at 12:03:08AM +0530, Srivatsa Bhat wrote:
>> You'll need CONFIG_LOCKDEP=y as well. An easy way to configure lock debugging
>> checks is to run 'make menuconfig' and enable the required options under the
>> "Kernel hacking" section.
>>
>> >
>> > If above configuration is all that I need, then should I be seeing warning/error
>> > messages in kernel logs(/var/log/kern.log) when there is inconsistency in
>> > locking ? To test my hypothesis, I modified my simple kernel module to
>> > deliberately induce locking error (After initializing read-write semaphore, I call
>> > down_write() and do not free this semaphore lock by commenting out up_write()
>> > invocation). But still I don't see any error or warning message trace in kernel
>> > logs, I think, I'm missing something.
>
> Hi Srivatsa,
>
> Thank you for your mail. As per your suggestion, this time I've enabled
> CONFIG_LOCKDEP aslo in my running kernel and did the same experiment, but still
> I dont't see any warning/error messages in the kernel log. To give you more idea
> about what I'm doing, Please see the code below.(This is a simple char driver
> based on LDD3 examples)
>
> <echo.c>
>
> #include <linux/module.h>
> #include <linux/init.h>
> #include <linux/types.h> //MAJOR, MINOR
> #include <linux/fs.h> //register_chrdev_region, file_operations
> #include <linux/moduleparam.h>
> #include <linux/kernel.h> //container_of
> #include <linux/slab.h> //kmalloc
> #include <linux/cdev.h> //struct cdev
> #include <linux/version.h>
> #include <linux/uaccess.h> //copy_from/to_user()
> #include <linux/errno.h> //error code
>
> ssize_t echo_read(struct file *, char __user *, size_t, loff_t *);
> ssize_t echo_write(struct file *, const char __user *, size_t, loff_t *);
> int echo_open(struct inode *, struct file *);
> int echo_release(struct inode *, struct file *);
>
> struct echo_cdev {
>? ? ? ? char *data;
>? ? ? ? unsigned long size; //amount of data stored
>? ? ? ? struct semaphore sem;
>? ? ? ? struct cdev cdev;
> };
> MODULE_LICENSE("GPL v2");
> MODULE_AUTHOR("amit");
>
> int nr_major;
> module_param(nr_major, int, S_IRUGO);
> MODULE_PARM_DESC(nr_major, "major number");
>
> int nr_minor;
> char *chrdev_name = "echo";
>
> static dev_t device;
> static int echo_dev_count = 1;
> struct echo_cdev *echo_dev = NULL;
>
> static struct file_operations echo_fs_ops = {
>? ? ? ? .open = echo_open,
>? ? ? ? .release = echo_release,
>? ? ? ? .read = echo_read,
>? ? ? ? .write = echo_write,
>? ? ? ? .owner = THIS_MODULE,
> };
>
> int echo_open(struct inode *inode, struct file *filp)
> {
>? ? ? ? struct echo_cdev *dev;
>? ? ? ? pr_debug("%s: f_flags: 0x%x\n",__FUNCTION__,filp->f_flags);
>? ? ? ? //container_of(pointer, container_type, container_field);
>? ? ? ? dev = container_of(inode->i_cdev, struct echo_cdev, cdev);
>? ? ? ? filp->private_data = dev;
>? ? ? ? if ((filp->f_flags & O_ACCMODE) == O_WRONLY) {
>? ? ? ? ? ? ? ? //trim the device size to 0
>? ? ? ? ? ? ? ? dev->size = 0;
>? ? ? ? }
>? ? ? ? return 0;
> }
>
> int echo_release(struct inode *inode, struct file *filp)
> {
>? ? ? ? return 0;
> }
>
> ssize_t echo_read(struct file *filp, char __user *ubuff, size_t count, loff_t *poffset)
> {
>? ? ? ? struct echo_cdev *dev = filp->private_data;
>? ? ? ? pr_debug("%s: f_flags: 0x%x\n",__FUNCTION__,filp->f_flags);
>
>? ? ? ? //user trying to access an offset which is beyond the end of file
>? ? ? ? if (down_interruptible(&dev->sem))
>? ? ? ? ? ? ? ? return -ERESTARTSYS;
>? ? ? ? if (*poffset >= dev->size) {
>? ? ? ? ? ? ? ? up(&dev->sem);
>? ? ? ? ? ? ? ? return 0;
>? ? ? ? }
>
>? ? ? ? //user trying to access more than eof, return bytes read till the eof
>? ? ? ? if (*poffset + count >= dev->size)
>? ? ? ? ? ? ? ? //count = dev->size - *poffset;
>? ? ? ? ? ? ? ? count = dev->size;
>? ? ? ? //kspace --> uspace
>? ? ? ? if (copy_to_user(ubuff, (dev->data + *poffset), count) < 0) {
>? ? ? ? ? ? ? ? up(&dev->sem);
>? ? ? ? ? ? ? ? return -EFAULT;
>? ? ? ? }
>? ? ? ? //update the offset
>? ? ? ? *poffset += count;
>? ? ? ? up(&dev->sem);
>? ? ? ? return count;
> }
>
> //count is the size of requested data transfer
> ssize_t echo_write(struct file *filp, const char __user *ubuff, size_t count, loff_t *poffset)
> {
>? ? ? ? int ret;
>? ? ? ? struct echo_cdev *dev = filp->private_data;
>? ? ? ? pr_debug("%s: f_flags: 0x%x\n",__FUNCTION__,filp->f_flags);
>? ? ? ? if (down_interruptible(&dev->sem))
>? ? ? ? ? ? ? ? return -ERESTARTSYS;
>? ? ? ? if (dev->data == NULL) {
>? ? ? ? ? ? ? ? dev->data = (char *)kmalloc(count, GFP_KERNEL);
>? ? ? ? ? ? ? ? if (!dev->data) {
>? ? ? ? ? ? ? ? ? ? ? ? up(&dev->sem);
>? ? ? ? ? ? ? ? ? ? ? ? return -ENOMEM;
>? ? ? ? ? ? ? ? } else {
>? ? ? ? ? ? ? ? ? ? ? ? memset(dev->data, 0, sizeof(count));
>? ? ? ? ? ? ? ? }
>? ? ? ? }
>? ? ? ? dev->size = count;
>? ? ? ? //uspace --> kspace
>? ? ? ? if (copy_from_user(dev->data, ubuff, count) < 0) {
>? ? ? ? ? ? ? ? up(&dev->sem);
>? ? ? ? ? ? ? ? return -EFAULT;
>? ? ? ? }
>
>? ? ? ? *poffset += count;
>? ? ? ? ret = count;
>
>? ? ? ? if (dev->size < *poffset)
>? ? ? ? ? ? ? ? dev->size = *poffset;
>? ? ? ? //Force lock error
>? ? ? ? //up(&dev->sem);
>? ? ? ? return ret;
> }
>
> static int __init echo_init(void)
> {
>? ? ? ? int ret;
>? ? ? ? printk(KERN_EMERG "entering %s\n",__FUNCTION__);
>? ? ? ? //let the user provide the major number.
>? ? ? ? if (nr_major) {
>? ? ? ? ? ? ? ? device = MKDEV(nr_major, nr_minor);
>? ? ? ? ? ? ? ? if ((ret = register_chrdev_region(device, echo_dev_count, chrdev_name)) < 0) {
>? ? ? ? ? ? ? ? ? ? ? ? pr_debug("%s: failed to register %s\n",__FUNCTION__,
>? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? chrdev_name);
>? ? ? ? ? ? ? ? ? ? ? ? return ret;
>? ? ? ? ? ? ? ? }
>? ? ? ? } else {
>? ? ? ? ? ? ? ? ret = alloc_chrdev_region(&device, 0, echo_dev_count, chrdev_name);
>? ? ? ? ? ? ? ? if (ret < 0) {
>? ? ? ? ? ? ? ? ? ? ? ? pr_debug("%s: failed to register %s\n",__FUNCTION__,
>? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? chrdev_name);
>? ? ? ? ? ? ? ? ? ? ? ? return ret;
>? ? ? ? ? ? ? ? }
>? ? ? ? }
>? ? ? ? nr_major = MAJOR(device);
>? ? ? ? nr_minor = MINOR(device);
>? ? ? ? //print the major and minor numbers
>? ? ? ? pr_debug("%s: major/minor:: %d/%d\n",__FUNCTION__,
>? ? ? ? ? ? ? ? ? ? ? ? nr_major, nr_minor);
>? ? ? ? echo_dev = (struct echo_cdev *)kmalloc(sizeof(struct echo_cdev), GFP_KERNEL);
>? ? ? ? if (!echo_dev) {
>? ? ? ? ? ? ? ? printk(KERN_EMERG "Not enough memory\n");
>? ? ? ? ? ? ? ? unregister_chrdev_region(device, echo_dev_count);
>? ? ? ? ? ? ? ? return -ENOMEM;
>? ? ? ? }
>? ? ? ? memset(echo_dev, 0, sizeof(struct echo_cdev));
>? ? ? ? echo_dev->cdev.owner = THIS_MODULE;
>? ? ? ? echo_dev->cdev.ops = &echo_fs_ops;
>? ? ? ? //initialize the semaphore, before it is presented to the world
>? ? ? ? sema_init(&echo_dev->sem,1);
>? ? ? ? cdev_init(&echo_dev->cdev, &echo_fs_ops);
>? ? ? ? device = MKDEV(nr_major, nr_minor);
>? ? ? ? //tell the kernel about this char device
>? ? ? ? //telling the VFS layer to associate echo driver's fs operation for file r/w etc.
>? ? ? ? ret = cdev_add(&echo_dev->cdev, device, 1);
>? ? ? ? if (ret) {
>? ? ? ? ? ? ? ? kfree(echo_dev);
>? ? ? ? ? ? ? ? unregister_chrdev_region(device, echo_dev_count);
>? ? ? ? ? ? ? ? return ret;
>? ? ? ? }
>? ? ? ? return 0;
> }
>
> static void __exit echo_exit(void)
> {
>? ? ? ? printk(KERN_EMERG "entering %s\n",__FUNCTION__);
>? ? ? ? if (echo_dev->data) {
>? ? ? ? ? ? ? ? printk("Inside %s: kfree()\n",__FUNCTION__);
>? ? ? ? ? ? ? ? kfree(echo_dev->data);
>? ? ? ? }
>? ? ? ? cdev_del(&echo_dev->cdev);
>? ? ? ? kfree(echo_dev);
>? ? ? ? unregister_chrdev_region(device, echo_dev_count);
> }
>
> module_init(echo_init);
> module_exit(echo_exit);
>
> <echo.c>
>
> <Makefile>
> obj-m := echo.o
> CFLAGS_echo.o := -DDEBUG -Wall -Werror -Wmissing-prototypes \
>? ? ? ? -Wstrict-prototypes -Wunused-variable -O2 \
>? ? ? ? -Wunused-function -g
>
> modules:
>? ? ? ? make -C /lib/modules/`uname -r`/build M=`pwd`
> clean:
>? ? ? ? make -C /lib/modules/`uname -r`/build M=`pwd` clean
> <Makefile>
>
> Logs:
> root at ubuntu:/boot# egrep -i "debug_kernel|lockdep"
> config-3.7.0-rc3-next-20121029
> CONFIG_LOCKDEP_SUPPORT=y
> CONFIG_DEBUG_KERNEL=y
> CONFIG_LOCKDEP=y
> # CONFIG_DEBUG_LOCKDEP is not set
>
> root at ubuntu:/home/amit/ldd3/misc-modules/echo# uname -a
> Linux ubuntu 3.7.0-rc3-next-20121029 #1 SMP Mon Oct 29 21:42:20 PDT 2012 i686
> i686 i386 GNU/Linux
>
> root at ubuntu:/home/amit/ldd3/misc-modules/echo# dmesg
>
> root at ubuntu:/home/amit/ldd3/misc-modules/echo# insmod echo.ko
>
> root at ubuntu:/home/amit/ldd3/misc-modules/echo# dmesg
> [ 1156.704072] entering echo_init
> [ 1156.704914] echo_init: major/minor:: 249/0
>
> root at ubuntu:/home/amit/ldd3/misc-modules/echo# mknod /dev/echo c 249 0
>
> root at ubuntu:/home/amit/ldd3/misc-modules/echo# ll /dev/echo
> crw-r--r-- 1 root root 249, 0 Oct 29 22:29 /dev/echo
>
> root at ubuntu:/home/amit/ldd3/misc-modules/echo# echo "kernel newbiee" >/dev/echo
>
> root at ubuntu:/home/amit/ldd3/misc-modules/echo# dmesg
> [ 1156.704072] entering echo_init
> [ 1156.704914] echo_init: major/minor:: 249/0
> [ 1237.377205] echo_open: f_flags: 0x8241
> [ 1237.377392] echo_write: f_flags: 0x8001
>
> root at ubuntu:/home/amit/ldd3/misc-modules/echo# cat /dev/echo
> --> Here the driver read routine gets stuck as I've not reliquished the
> semaphore lock
>
> root at ubuntu:/home/amit/ldd3/misc-modules/echo# cat /dev/echo
> ^C <-- killing the user process
>
> root at ubuntu:/home/amit/ldd3/misc-modules/echo# rmmod echo
>
> root at ubuntu:/home/amit/ldd3/misc-modules/echo# dmesg
> [ 1156.704072] entering echo_init
> [ 1156.704914] echo_init: major/minor:: 249/0
> [ 1237.377205] echo_open: f_flags: 0x8241
> [ 1237.377392] echo_write: f_flags: 0x8001
> [ 1270.622337] echo_open: f_flags: 0x8000
> [ 1270.622477] echo_read: f_flags: 0x8000
> [ 1394.180962] entering echo_exit
> [ 1394.180996] Inside echo_exit: kfree()
>
> As you can see, no warning/error messages reported by kernel.
> -Amit
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Hi
I've not tried your module, but I suppose that you should get warning
as soon as you try to take write semaphore once again.
Best wishes
Vladimir Murzin
_______________________________________________
Kernelnewbies mailing list
Kernelnewbies at kernelnewbies.org
http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
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^ permalink raw reply [flat|nested] 8+ messages in thread
* Tools for checking incorrect usage of locking techniques in k-space
2012-11-05 5:51 ` Vladimir Murzin
2012-11-05 7:24 ` Anand Moon
@ 2012-11-06 9:30 ` Kumar amit mehta
1 sibling, 0 replies; 8+ messages in thread
From: Kumar amit mehta @ 2012-11-06 9:30 UTC (permalink / raw)
To: kernelnewbies
On Mon, Nov 05, 2012 at 09:51:19AM +0400, Vladimir Murzin wrote:
> I've not tried your module, but I suppose that you should get warning
> as soon as you try to take write semaphore once again.
>
Thank you for your mail. I wanted to try what you've suggested, but now I'm
facing a different problem. For kernel-janitorial purpose I sync my local repo
to the linux-next tree almost everyday and once in a while I build and boot
from the latest kernel from the linux-next tree. But most of the time, After
syncing to the latest linux-next tree, I perform only following steps to build
some staging drivers under linux-next tree:
>From the top of the latest linux-next tree:
# make oldconfig
# make prepare
# make modules_prepare
# make M=drivers/staging/<some driver>
The above steps work fine, except that I get some warning message.
<snip>
WARNING: Symbol version dump /home/amit/lkernel/Module.symvers
is missing; modules will have no dependencies and modversions.
<snip>
So my understanding is that I've booted from version-X and the linux-next kernel
version is version-Y and because of this version mismatch, I see the above
WARNING message. Now, because of this kernel version mismatch I am not able to
insert the module. An attempt to do so returns following error message:
root at ubuntu:/home/amit/ldd3/misc-modules/echo# insmod echo.ko
insmod: error inserting 'echo.ko': -1 Invalid module format
Some information regarding my setup:
amit at ubuntu:~/ldd3/misc-modules/echo$ uname -r
3.7.0-rc3-next-20121029
amit at ubuntu:~/ldd3/misc-modules/echo$ ll /lib/modules/`uname -r`/build
lrwxrwxrwx 1 root root 18 Oct 29 22:02
/lib/modules/3.7.0-rc3-next-20121029/build -> /home/amit/lkernel/
Here the /lib/modules/3.7.0-rc3-next-20121029/build is a softlink to the latest
kernel sources.
If I try to install the header files for my current kernel(returned by 'uname
-r'), I get following error message:
<snip>
amit at ubuntu:~$ sudo apt-get install linux-headers-$(uname -r)
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package linux-headers-3.7.0-rc3-next-20121029
E: Couldn't find any package by regex 'linux-headers-3.7.0-rc3-next-20121029'
<snip>
How do I ovecome this ? Do I need to build the latest kernel(linux-next) and
boot from it, whenever I sync my local linux-next repository with the remote?
I'd like to be able to check my local changes by building and loading the
module/subsystem.
-Amit
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2012-11-06 9:30 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2012-10-27 4:41 Tools for checking incorrect usage of locking techniques in k-space Kumar amit mehta
2012-10-27 15:56 ` Srivatsa Bhat
2012-10-27 19:06 ` Kumar amit mehta
2012-10-28 18:33 ` Srivatsa Bhat
2012-10-30 5:41 ` Kumar amit mehta
2012-11-05 5:51 ` Vladimir Murzin
2012-11-05 7:24 ` Anand Moon
2012-11-06 9:30 ` Kumar amit mehta
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