Deleting The Head of The List in Linux Kernel

We are developing a kernel device. There is a list in a device that keeps the messages. We want to delete the head of the list. The related part of the code is below:

Device Message and Device Struct:

typedef struct dev_message

{

    char *data;

    int *message_count;

    struct list_head list;

}device_message;





typedef struct queue_dev

{

    device_message *message_head;

    struct semaphore sem;

    struct cdev cdev;

}queue_device;

Adding to head of the list is done with

INIT_LIST_HEAD(&(dev->message_head->list));

and adding the other entries are done with

list_add_tail(&newMsg->list,&dev->message_head->list);

We can delete every element of the list except the head of the list. How can we delete the only head of the list?
Sincerely.

asked Nov 28 '18 at 18:54

Latif Uluman

Are you saying that when you call LIST_REMOVE it can't find the element at the head of the list?

– bruceg
Nov 28 '18 at 19:14

You are not showing any of the code for deletion, which makes this hard to debug. However, since the head of a list is generally not stored in a list node, but in an indepenent location, it takes special handling to delete it. See for example this question.

– AShelly
Nov 28 '18 at 19:39

kernel lists expect you to keep one extra list_head for each list. Every element is also a list_head so a list of N has N+1 list_heads. Deleting the 1st element is no different from deleting one in the middle.

– stark
Nov 28 '18 at 20:15

@AShelly when we implement our design, we did not know the information about the storage of the head of the list. We have used another approach to the the task. Thank you for the information. Additionally, thanks for other people they try to hepl me.

– Latif Uluman
Nov 29 '18 at 5:38

When writing kernel code I would advise you to strictly adhere to the style of the other device drivers.

– stark
Nov 29 '18 at 12:19

|
show 1 more comment

We are developing a kernel device. There is a list in a device that keeps the messages. We want to delete the head of the list. The related part of the code is below:

Device Message and Device Struct:

typedef struct dev_message

{

    char *data;

    int *message_count;

    struct list_head list;

}device_message;





typedef struct queue_dev

{

    device_message *message_head;

    struct semaphore sem;

    struct cdev cdev;

}queue_device;

Adding to head of the list is done with

INIT_LIST_HEAD(&(dev->message_head->list));

and adding the other entries are done with

list_add_tail(&newMsg->list,&dev->message_head->list);

We can delete every element of the list except the head of the list. How can we delete the only head of the list?
Sincerely.

asked Nov 28 '18 at 18:54

Latif Uluman

Are you saying that when you call LIST_REMOVE it can't find the element at the head of the list?

– bruceg
Nov 28 '18 at 19:14

You are not showing any of the code for deletion, which makes this hard to debug. However, since the head of a list is generally not stored in a list node, but in an indepenent location, it takes special handling to delete it. See for example this question.

– AShelly
Nov 28 '18 at 19:39

kernel lists expect you to keep one extra list_head for each list. Every element is also a list_head so a list of N has N+1 list_heads. Deleting the 1st element is no different from deleting one in the middle.

– stark
Nov 28 '18 at 20:15

@AShelly when we implement our design, we did not know the information about the storage of the head of the list. We have used another approach to the the task. Thank you for the information. Additionally, thanks for other people they try to hepl me.

– Latif Uluman
Nov 29 '18 at 5:38

When writing kernel code I would advise you to strictly adhere to the style of the other device drivers.

– stark
Nov 29 '18 at 12:19

|
show 1 more comment

We are developing a kernel device. There is a list in a device that keeps the messages. We want to delete the head of the list. The related part of the code is below:

Device Message and Device Struct:

typedef struct dev_message

{

    char *data;

    int *message_count;

    struct list_head list;

}device_message;





typedef struct queue_dev

{

    device_message *message_head;

    struct semaphore sem;

    struct cdev cdev;

}queue_device;

Adding to head of the list is done with

INIT_LIST_HEAD(&(dev->message_head->list));

and adding the other entries are done with

list_add_tail(&newMsg->list,&dev->message_head->list);

We can delete every element of the list except the head of the list. How can we delete the only head of the list?
Sincerely.

asked Nov 28 '18 at 18:54

Latif Uluman

We are developing a kernel device. There is a list in a device that keeps the messages. We want to delete the head of the list. The related part of the code is below:

Device Message and Device Struct:

typedef struct dev_message

{

    char *data;

    int *message_count;

    struct list_head list;

}device_message;





typedef struct queue_dev

{

    device_message *message_head;

    struct semaphore sem;

    struct cdev cdev;

}queue_device;

Adding to head of the list is done with

INIT_LIST_HEAD(&(dev->message_head->list));

and adding the other entries are done with

list_add_tail(&newMsg->list,&dev->message_head->list);

We can delete every element of the list except the head of the list. How can we delete the only head of the list?
Sincerely.

c linked-list linux-kernel

asked Nov 28 '18 at 18:54

Latif Uluman

asked Nov 28 '18 at 18:54

Latif Uluman

asked Nov 28 '18 at 18:54

Latif Uluman

asked Nov 28 '18 at 18:54

Latif Uluman

asked Nov 28 '18 at 18:54

Latif Uluman

Are you saying that when you call LIST_REMOVE it can't find the element at the head of the list?

– bruceg
Nov 28 '18 at 19:14

You are not showing any of the code for deletion, which makes this hard to debug. However, since the head of a list is generally not stored in a list node, but in an indepenent location, it takes special handling to delete it. See for example this question.

– AShelly
Nov 28 '18 at 19:39

kernel lists expect you to keep one extra list_head for each list. Every element is also a list_head so a list of N has N+1 list_heads. Deleting the 1st element is no different from deleting one in the middle.

– stark
Nov 28 '18 at 20:15

@AShelly when we implement our design, we did not know the information about the storage of the head of the list. We have used another approach to the the task. Thank you for the information. Additionally, thanks for other people they try to hepl me.

– Latif Uluman
Nov 29 '18 at 5:38

When writing kernel code I would advise you to strictly adhere to the style of the other device drivers.

– stark
Nov 29 '18 at 12:19

|
show 1 more comment

Are you saying that when you call LIST_REMOVE it can't find the element at the head of the list?

– bruceg
Nov 28 '18 at 19:14

You are not showing any of the code for deletion, which makes this hard to debug. However, since the head of a list is generally not stored in a list node, but in an indepenent location, it takes special handling to delete it. See for example this question.

– AShelly
Nov 28 '18 at 19:39

kernel lists expect you to keep one extra list_head for each list. Every element is also a list_head so a list of N has N+1 list_heads. Deleting the 1st element is no different from deleting one in the middle.

– stark
Nov 28 '18 at 20:15

@AShelly when we implement our design, we did not know the information about the storage of the head of the list. We have used another approach to the the task. Thank you for the information. Additionally, thanks for other people they try to hepl me.

– Latif Uluman
Nov 29 '18 at 5:38

When writing kernel code I would advise you to strictly adhere to the style of the other device drivers.

– stark
Nov 29 '18 at 12:19

Are you saying that when you call LIST_REMOVE it can't find the element at the head of the list?

– bruceg
Nov 28 '18 at 19:14

You are not showing any of the code for deletion, which makes this hard to debug. However, since the head of a list is generally not stored in a list node, but in an indepenent location, it takes special handling to delete it. See for example this question.

– AShelly
Nov 28 '18 at 19:39

kernel lists expect you to keep one extra list_head for each list. Every element is also a list_head so a list of N has N+1 list_heads. Deleting the 1st element is no different from deleting one in the middle.

– stark
Nov 28 '18 at 20:15

@AShelly when we implement our design, we did not know the information about the storage of the head of the list. We have used another approach to the the task. Thank you for the information. Additionally, thanks for other people they try to hepl me.

– Latif Uluman
Nov 29 '18 at 5:38

When writing kernel code I would advise you to strictly adhere to the style of the other device drivers.

– stark
Nov 29 '18 at 12:19

|
show 1 more comment

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