diff -r 4816d766a08a -r f345bda72bc4 Symbian3/PDK/Source/GUID-1F280171-A3F3-4129-8DBE-3B1C4D629C68.dita --- a/Symbian3/PDK/Source/GUID-1F280171-A3F3-4129-8DBE-3B1C4D629C68.dita Tue Mar 30 11:42:04 2010 +0100 +++ b/Symbian3/PDK/Source/GUID-1F280171-A3F3-4129-8DBE-3B1C4D629C68.dita Tue Mar 30 11:56:28 2010 +0100 @@ -1,235 +1,235 @@ - - - - - -Atomic -OperationsDescribes the new atomic operations added to euser.dll and -the kernel. -

An atomic operation is an operation that comprises two or more conditions. -When an atomic operation is executed and all conditions are met it results -in success; when one or more conditions are not met it results in failure. -The new atomic operations added to euser.dll and the kernel -replace the existing ones. The existing operation format is preserved __e32_atomic_xxx_yyyZ

-

In the above format:

- -

The following table outlines the types of memory ordering and operations -available.

- - - - -Memory Ordering (yyy) - - -Name -Description - - -rlx -Relaxed memory ordering. In this type of ordering there is no fixed -order in which the atomic operation is observed in relation to other memory -operations. - - -acq -Acquire semantics. In this type of memory ordering a memory barrier -is placed after the atomic operation. - - -rel -Release semantics. In this type of ordering a memory barrier is executed -before the atomic operation. - - -ord -Fully ordered. In this type of ordering a memory barrier is executed -before and after the atomic operation. - - -Operation (xxx) - - -Name -Description - - -load -Reads the contents of a location. - - -store -Writes to a location - - -swp -Swaps the contents of a specified memory location with a given parameter. - - -add -Adds a value to the contents of the specified memory location. - - -and -Logical AND. - - -ior -Logical OR. - - -xor -Logical XOR. - - -axo - AND then XOR - - -cas -Compare and Set

Compare the contents of the specified memory location -with another specified location. If the contents of both locations have the -same value, the contents of the original location is set to a specified value.

 - - -tau -Threshold and add unsigned

If the contents of a specified memory -location is greater than the specified threshold, then add the contents with -one parameter, otherwise add the contents to another. For this operation, -all the parameters are unsigned.

 - - -tas - Threshold and add signed

If the contents of a specified memory location -is greater than the specified threshold, then add the contents with one parameter, -otherwise add the contents to another. For this operation, all the parameters -are signed.

 - - - -
-

The meaning of each parameter, depends on the operation (xxx) (the argument -order is from left to right) :

- - - - -Operation (xxx) -First argument -Second Argument -Third Argument -Fourth Argument - - -load -address of the data -N/A -N/A -N/A - - -store -address of the data -Data to be stored. -N/A -N/A - - -swp -address of the data -Data to be swapped. -N/A -N/A - - -cas -address of the data -Address of the data to be compared. -New contents of the address specified in the first parameter, -if the comparison is true. -N/A - - -add -address of the data -Data to be added. -N/A -N/A - - -and -address of the data -Data to be used in the AND operation . -N/A -N/A - - -ior -address of the data -Data to be used in the OR operation. -N/A -N/A - - -xor -address of the data -Data to be used in the XOR operation. -N/A -N/A - - -axo -address of the data -Data to be used in the AND operation. -Data to be used in the XOR operation. -N/A - - -tau -address of the data -Value of the threshold. -See note 1. -See note 2. - - -tas -address of the data -Value of the threshold. -See note 1. -See note 2. - - - -
-

Note:

-

1. Value to add if the value of the data pointed to by the address in -the first parameter, is equal to or greater than the threshold value

-

2. Value to add if the value of the data pointed to by the address in the -first parameter, is less than the threshold.

-
Example -

An example of an atomic operation in use is :

if (__e32_atomic_tas_ord32(&buffer.iDisplayDriverCount, 1, -1, 0) == 1) - { - // All drivers disconnected, deallocate memory. - ... - }

In the above example we use a fully ordered -memory to compare a threshold value of 1. If the value of &buffer.iDisplayDriverCount is -greater than or equal to 1 then it is added with -1 and the final value of &buffer.iDisplayDriverCount is -returned. If the value of &buffer.iDisplayDriverCount is -not greater than or equal to 1, the value of &buffer.iDisplayDriverCount is -added with 0 and returned. The driver are disconnected when the returned value -is equal to 1.

- -Maintaining -Data Integrity Using Memory Barriers + + + + + +Atomic +OperationsDescribes the new atomic operations added to euser.dll and +the kernel. +

An atomic operation is an operation that comprises two or more conditions. +When an atomic operation is executed and all conditions are met it results +in success; when one or more conditions are not met it results in failure. +The new atomic operations added to euser.dll and the kernel +replace the existing ones. The existing operation format is preserved __e32_atomic_xxx_yyyZ

+

In the above format:

+
    +

  • z specifies the size of the data type being operated on

    • +

  • yyy specifies the type of memory ordering that is to be enforced (with +memory barriers)

    • +

  • xxx specifies the operation that is to be performed.

    • +
+

The following table outlines the types of memory ordering and operations +available.

+ + + + +Memory Ordering (yyy) + + +Name +Description + + +rlx +Relaxed memory ordering. In this type of ordering there is no fixed +order in which the atomic operation is observed in relation to other memory +operations. + + +acq +Acquire semantics. In this type of memory ordering a memory barrier +is placed after the atomic operation. + + +rel +Release semantics. In this type of ordering a memory barrier is executed +before the atomic operation. + + +ord +Fully ordered. In this type of ordering a memory barrier is executed +before and after the atomic operation. + + +Operation (xxx) + + +Name +Description + + +load +Reads the contents of a location. + + +store +Writes to a location + + +swp +Swaps the contents of a specified memory location with a given parameter. + + +add +Adds a value to the contents of the specified memory location. + + +and +Logical AND. + + +ior +Logical OR. + + +xor +Logical XOR. + + +axo + AND then XOR + + +cas +Compare and Set

Compare the contents of the specified memory location +with another specified location. If the contents of both locations have the +same value, the contents of the original location is set to a specified value.

 + + +tau +Threshold and add unsigned

If the contents of a specified memory +location is greater than the specified threshold, then add the contents with +one parameter, otherwise add the contents to another. For this operation, +all the parameters are unsigned.

 + + +tas + Threshold and add signed

If the contents of a specified memory location +is greater than the specified threshold, then add the contents with one parameter, +otherwise add the contents to another. For this operation, all the parameters +are signed.

 + + + +
+

The meaning of each parameter, depends on the operation (xxx) (the argument +order is from left to right) :

+ + + + +Operation (xxx) +First argument +Second Argument +Third Argument +Fourth Argument + + +load +address of the data +N/A +N/A +N/A + + +store +address of the data +Data to be stored. +N/A +N/A + + +swp +address of the data +Data to be swapped. +N/A +N/A + + +cas +address of the data +Address of the data to be compared. +New contents of the address specified in the first parameter, +if the comparison is true. +N/A + + +add +address of the data +Data to be added. +N/A +N/A + + +and +address of the data +Data to be used in the AND operation . +N/A +N/A + + +ior +address of the data +Data to be used in the OR operation. +N/A +N/A + + +xor +address of the data +Data to be used in the XOR operation. +N/A +N/A + + +axo +address of the data +Data to be used in the AND operation. +Data to be used in the XOR operation. +N/A + + +tau +address of the data +Value of the threshold. +See note 1. +See note 2. + + +tas +address of the data +Value of the threshold. +See note 1. +See note 2. + + + +
+

+

1. Value to add if the value of the data pointed to by the address in +the first parameter, is equal to or greater than the threshold value

+

2. Value to add if the value of the data pointed to by the address in the +first parameter, is less than the threshold.

+
Example +

An example of an atomic operation in use is :

if (__e32_atomic_tas_ord32(&buffer.iDisplayDriverCount, 1, -1, 0) == 1) + { + // All drivers disconnected, deallocate memory. + ... + }

In the above example we use a fully ordered +memory to compare a threshold value of 1. If the value of &buffer.iDisplayDriverCount is +greater than or equal to 1 then it is added with -1 and the final value of &buffer.iDisplayDriverCount is +returned. If the value of &buffer.iDisplayDriverCount is +not greater than or equal to 1, the value of &buffer.iDisplayDriverCount is +added with 0 and returned. The driver are disconnected when the returned value +is equal to 1.

+ +SMP - Overview + \ No newline at end of file