list_entry return value

Hay guys!

I'm changing the kernel code at the Rat Hat OS and I want to use the macro开发者_运维百科 "list entry". I can't find anywhere what is the return value in case of failure..

What will it return if the list is empty? or at any other case...

Thanks!! Ami

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It should be something undefined if the list is empty. (You're trying to dereference a list pointer that's not in a struct of the list's element type)

Generally, if you must use list_entry directly, you want to check if list_empty first. This will verify your list head doesn't point to itself.

Otherwise stick to always using the list_for_each macros which will generate a for loop over your elements.

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We can use this list_head in two ways

1) independent single global variable, to HOLD the list as head to all

we can not use the list_entry on this variable event though there are list members in it. because this is not part of any structure.

2) we can use list_head as member of the your structure, wile adding to the list you will give this member pointer to the list HEAD.

we will use list_entry on this member to get the your structure even though your list member is not part of any List(it initialized with next=NULL and priv=NULL) you can get structure there is no way to fail.

list_entry is simple container_of() we use this to get the structure pointer using member pointer.