Analysis of commonly used list in Linux (6)

Describes the iterate over functions of a list:
1. # define list_for_each (Pos, head )/
For (Pos = (head)-> next; prefetch (POS-> next), pos! = (Head );/
Pos = pos-> next)
There seems to be nothing to say about this traversal loop. Starting from head-> next, we use the next pointer to traverse the loop. prefetch pushes the pointer into the CPU L1 cache.

# DEFINE _ list_for_each (Pos, head )/
For (Pos = (head)-> next; pos! = (Head); Pos = pos-> next)
The prefetch operation is missing.

# Define list_for_each_prev (Pos, head )/
For (Pos = (head)-> Prev; prefetch (POS-> PREV), pos! = (Head );/
Pos = pos-> PREV)
This is an operation with prefetch that is traversed using the prev pointer.

# Define list_for_each_safe (Pos, N, head )/
For (Pos = (head)-> next, n = pos-> next; pos! = (Head );/
Pos = n, n = pos-> next)
Safe iterate over function. parameter n is a linked list for temporary storage.

2. # define list_for_each_entry (Pos, Head, member )/
For (Pos = list_entry (head)-> next, typeof (* POS), member );/
Prefetch (POS-> member. Next), & Pos-> member! = (Head );/
Pos = list_entry (POS-> member. Next, typeof (* POS), member ))
This function uses the well-known list_entry that has been explained previously, namely the container_of function.
POS is a type-structured pointer, head is the list header node, and member is a member of struct.
We can see that this function uses the next pointer to traverse member members.

# Define list_for_each_entry_reverse (Pos, Head, member )/
For (Pos = list_entry (head)-> Prev, typeof (* POS), member );/
Prefetch (POS-> member. Prev), & Pos-> member! = (Head);/# define list_for_each_entry_from (Pos, Head, member )/
For (; prefetch (POS-> member. Next), & Pos-> member! = (Head );/
Pos = list_entry (POS-> member. Next, typeof (* POS), member ))
Pos = list_entry (POS-> member. Prev, typeof (* POS), member ))
Same as above, it uses the prev pointer to traverse member members.

# Define list_prepare_entry (Pos, Head, member )/
(POS )? : List_entry (Head, typeof (* POS), member ))
Obtain the POs pointer for list_for_each_entry_continuer (). If the POS is empty, obtain the Member member entry address of the head node.

# Define list_for_each_entry_continue (Pos, Head, member )/
For (Pos = list_entry (POS-> member. Next, typeof (* POS), member );/
Prefetch (POS-> member. Next), & Pos-> member! = (Head );/
Pos = list_entry (POS-> member. Next, typeof (* POS), member ))
Use the next pointer to traverse member members starting from POS.

# Define list_for_each_entry_from (Pos, Head, member )/
For (; prefetch (POS-> member. Next), & Pos-> member! = (Head );/
Pos = list_entry (POS-> member. Next, typeof (* POS), member ))
Use the next pointer to traverse the members starting from the current position.

3. The Safe series and RCU system functions are similar to the above and are no longer repeated.