Overview
To update values shared between multiple threads, use the functions below.
They ensure that the values are atomically updated, i.e. that the memory
reads, the updates, and the memory writes are done in the right order.
These functions are slower than their non-atomic equivalents, so use
them only when synchronization is needed.
Note that in RenderScript, your code is likely to be running in separate
threads even though you did not explicitely create them. The RenderScript
runtime will very often split the execution of one kernel across multiple
threads. Updating globals should be done with atomic functions. If possible,
modify your algorithm to avoid them altogether.
Summary
Functions
rsAtomicAdd
: Thread-safe addition
Parameters
| addr | Address of the value to modify. |
|---|
| value | Amount to add. |
|---|
Returns
| Value of *addr prior to the operation. |
Atomicly adds a value to the value at addr, i.e. *addr += value.
rsAtomicAnd
: Thread-safe bitwise and
Parameters
| addr | Address of the value to modify. |
|---|
| value | Value to and with. |
|---|
Returns
| Value of *addr prior to the operation. |
Atomicly performs a bitwise and of two values, storing the result back at addr,
i.e. *addr &= value.
rsAtomicCas
: Thread-safe compare and set
Parameters
| addr | Address of the value to compare and replace if the test passes. |
|---|
| compareValue | Value to test *addr against. |
|---|
| newValue | Value to write if the test passes. |
|---|
Returns
| Value of *addr prior to the operation. |
If the value at addr matches compareValue then the newValue is written at addr,
i.e. if (*addr == compareValue) { *addr = newValue; }.
You can check that the value was written by checking that the value returned
by rsAtomicCas() is compareValue.
rsAtomicDec
: Thread-safe decrement
Parameters
| addr | Address of the value to decrement. |
|---|
Returns
| Value of *addr prior to the operation. |
Atomicly subtracts one from the value at addr. This is equivalent to rsAtomicSub(addr, 1).
rsAtomicInc
: Thread-safe increment
Parameters
| addr | Address of the value to increment. |
|---|
Returns
| Value of *addr prior to the operation. |
Atomicly adds one to the value at addr. This is equivalent to rsAtomicAdd(addr, 1).
rsAtomicMax
: Thread-safe maximum
Parameters
| addr | Address of the value to modify. |
|---|
| value | Comparison value. |
|---|
Returns
| Value of *addr prior to the operation. |
Atomicly sets the value at addr to the maximum of *addr and value, i.e.
*addr = max(*addr, value).
rsAtomicMin
: Thread-safe minimum
Parameters
| addr | Address of the value to modify. |
|---|
| value | Comparison value. |
|---|
Returns
| Value of *addr prior to the operation. |
Atomicly sets the value at addr to the minimum of *addr and value, i.e.
*addr = min(*addr, value).
rsAtomicOr
: Thread-safe bitwise or
Parameters
| addr | Address of the value to modify. |
|---|
| value | Value to or with. |
|---|
Returns
| Value of *addr prior to the operation. |
Atomicly perform a bitwise or two values, storing the result at addr,
i.e. *addr |= value.
rsAtomicSub
: Thread-safe subtraction
Parameters
| addr | Address of the value to modify. |
|---|
| value | Amount to subtract. |
|---|
Returns
| Value of *addr prior to the operation. |
Atomicly subtracts a value from the value at addr, i.e. *addr -= value.
rsAtomicXor
: Thread-safe bitwise exclusive or
Parameters
| addr | Address of the value to modify. |
|---|
| value | Value to xor with. |
|---|
Returns
| Value of *addr prior to the operation. |
Atomicly performs a bitwise xor of two values, storing the result at addr,
i.e. *addr ^= value.
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