is pointer assignment atomic in golang

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Is assigning a pointer atomic in go #38667

SmallSmartMouse commented Apr 26, 2020

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How to use Atomic Pointers in Golang 1.19

“Atomic” in computer programming refers to performing operations one at a time. Objective-C has atomic properties. It ensures a safe reading and writing to a property from different threads. In Objective-C, it is used with immutable types. This is because immutable types are really “recreated” to change it. In other words, changing an immutable type in your code will not cause the compiler to throw an error. However, it’ll instantiate a new object when you do so. A prime example is Go’s append function, it makes a new array for each invocation. In Obj-C, atomic properties will ensure operations are performed one after another to prevent threads from accessing a memory address simultaneously. Since Go is multithreaded, it supports atomic operations as well. Golang 1.19 introduces new atomic types. My favorite addition is atomic.Pointer , it provides a sleek alternative to atomic.Value . It’s also a great showcase of how generics enhance the developer experience.

The Go 1.19 atomic.Pointer

atomic.Pointer is a generic type. Unlike Value , it does not require asserting your stored value to access it. Here is a code block that defines and stores a pointer :

I instantiate variable p as a struct literal. I then proceed to store the pointer of the variable s in p , s represents a server connection. Voila, we’ve passed the first step toward atomicity. By storing the variable as an atomic value, we’ll ensure that there is no simultaneous access to the memory address. For example, maps will cause a program to panic if it is read and written simultaneously. As are atomic operations, locks are a great way to prevent these panics.

Golang Atomic Pointer use cases

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Atomic Operations in Golang – atomic package

Atomic operations are those which are implemented at the hardware level. Go has the atomic package which helps to achieve synchronization when doing concurrency. In this post, we will see what the atomic package has to offer.

What is an atomic operation?

If we do an operation like increment or decrement using channels on a single shared variable, the goroutines will not be synchronized and will produce erroneous output. The atomic operations, on the other hand, are implemented at the hardware level. That means when we create a shared atomic variable and use multiple goroutines to update its value it will be updated correctly.

Importing Golang atomic package

To use the atomic functions we need to import the sync/atomic package.

Atomic functions in Golang

The package contains load, store and the addition operation for the int32, int 64, uint32, uint64, etc. Since only ints are such primitive that can be correctly synchronized using atomics.

Let’s see an example of what can happen if we don’t use atomic.

As can be seen each time the program is run it will produce the wrong output. It happens due to the fact the goroutines accessing and changing the value is not synchronized. So, the changed values are arbitrary and will result in the wrong number of operations.

Now, we convert the code above to synchronized code using atomic.

Now, each time we run it, it will produce the correct output. Since the atomic operations are synchronized it will return the correct output no matter what.

Use of atomic operations in Golang

Atomic operations are used when we need to have a shared variable between different goroutines which will be updated by them. If the updating operation is not synchronized then it will create a problem that we saw.

Atomic operations solve that problem by synchronizing access to the shared variable and making the output correct.

This package is not in the latest version of its module.

Documentation ¶

Package atomic provides low-level atomic memory primitives useful for implementing synchronization algorithms.

These functions require great care to be used correctly. Except for special, low-level applications, synchronization is better done with channels or the facilities of the sync package. Share memory by communicating; don't communicate by sharing memory.

The swap operation, implemented by the SwapT functions, is the atomic equivalent of:

The compare-and-swap operation, implemented by the CompareAndSwapT functions, is the atomic equivalent of:

The add operation, implemented by the AddT functions, is the atomic equivalent of:

The load and store operations, implemented by the LoadT and StoreT functions, are the atomic equivalents of "return *addr" and "*addr = val".

In the terminology of the Go memory model, if the effect of an atomic operation A is observed by atomic operation B, then A “synchronizes before” B. Additionally, all the atomic operations executed in a program behave as though executed in some sequentially consistent order. This definition provides the same semantics as C++'s sequentially consistent atomics and Java's volatile variables.

func AddInt32(addr *int32, delta int32) (new int32)
func AddInt64(addr *int64, delta int64) (new int64)
func AddUint32(addr *uint32, delta uint32) (new uint32)
func AddUint64(addr *uint64, delta uint64) (new uint64)
func AddUintptr(addr *uintptr, delta uintptr) (new uintptr)
func CompareAndSwapInt32(addr *int32, old, new int32) (swapped bool)
func CompareAndSwapInt64(addr *int64, old, new int64) (swapped bool)
func CompareAndSwapPointer(addr *unsafe.Pointer, old, new unsafe.Pointer) (swapped bool)
func CompareAndSwapUint32(addr *uint32, old, new uint32) (swapped bool)
func CompareAndSwapUint64(addr *uint64, old, new uint64) (swapped bool)
func CompareAndSwapUintptr(addr *uintptr, old, new uintptr) (swapped bool)
func LoadInt32(addr *int32) (val int32)
func LoadInt64(addr *int64) (val int64)
func LoadPointer(addr *unsafe.Pointer) (val unsafe.Pointer)
func LoadUint32(addr *uint32) (val uint32)
func LoadUint64(addr *uint64) (val uint64)
func LoadUintptr(addr *uintptr) (val uintptr)
func StoreInt32(addr *int32, val int32)
func StoreInt64(addr *int64, val int64)
func StorePointer(addr *unsafe.Pointer, val unsafe.Pointer)
func StoreUint32(addr *uint32, val uint32)
func StoreUint64(addr *uint64, val uint64)
func StoreUintptr(addr *uintptr, val uintptr)
func SwapInt32(addr *int32, new int32) (old int32)
func SwapInt64(addr *int64, new int64) (old int64)
func SwapPointer(addr *unsafe.Pointer, new unsafe.Pointer) (old unsafe.Pointer)
func SwapUint32(addr *uint32, new uint32) (old uint32)
func SwapUint64(addr *uint64, new uint64) (old uint64)
func SwapUintptr(addr *uintptr, new uintptr) (old uintptr)
func (x *Bool) CompareAndSwap(old, new bool) (swapped bool)
func (x *Bool) Load() bool
func (x *Bool) Store(val bool)
func (x *Bool) Swap(new bool) (old bool)
func (x *Int32) Add(delta int32) (new int32)
func (x *Int32) CompareAndSwap(old, new int32) (swapped bool)
func (x *Int32) Load() int32
func (x *Int32) Store(val int32)
func (x *Int32) Swap(new int32) (old int32)
func (x *Int64) Add(delta int64) (new int64)
func (x *Int64) CompareAndSwap(old, new int64) (swapped bool)
func (x *Int64) Load() int64
func (x *Int64) Store(val int64)
func (x *Int64) Swap(new int64) (old int64)
type Pointer
func (x *Pointer[T]) CompareAndSwap(old, new *T) (swapped bool)
func (x *Pointer[T]) Load() *T
func (x *Pointer[T]) Store(val *T)
func (x *Pointer[T]) Swap(new *T) (old *T)
type Uint32
func (x *Uint32) Add(delta uint32) (new uint32)
func (x *Uint32) CompareAndSwap(old, new uint32) (swapped bool)
func (x *Uint32) Load() uint32
func (x *Uint32) Store(val uint32)
func (x *Uint32) Swap(new uint32) (old uint32)
type Uint64
func (x *Uint64) Add(delta uint64) (new uint64)
func (x *Uint64) CompareAndSwap(old, new uint64) (swapped bool)
func (x *Uint64) Load() uint64
func (x *Uint64) Store(val uint64)
func (x *Uint64) Swap(new uint64) (old uint64)
type Uintptr
func (x *Uintptr) Add(delta uintptr) (new uintptr)
func (x *Uintptr) CompareAndSwap(old, new uintptr) (swapped bool)
func (x *Uintptr) Load() uintptr
func (x *Uintptr) Store(val uintptr)
func (x *Uintptr) Swap(new uintptr) (old uintptr)
func (v *Value) CompareAndSwap(old, new any) (swapped bool)
func (v *Value) Load() (val any)
func (v *Value) Store(val any)
func (v *Value) Swap(new any) (old any)
Value (Config)
Value (ReadMostly)

Constants ¶

This section is empty.

Variables ¶

Functions ¶, func addint32 ¶.

AddInt32 atomically adds delta to *addr and returns the new value. Consider using the more ergonomic and less error-prone Int32.Add instead.

func AddInt64 ¶

AddInt64 atomically adds delta to *addr and returns the new value. Consider using the more ergonomic and less error-prone Int64.Add instead (particularly if you target 32-bit platforms; see the bugs section).

func AddUint32 ¶

AddUint32 atomically adds delta to *addr and returns the new value. To subtract a signed positive constant value c from x, do AddUint32(&x, ^uint32(c-1)). In particular, to decrement x, do AddUint32(&x, ^uint32(0)). Consider using the more ergonomic and less error-prone Uint32.Add instead.

func AddUint64 ¶

AddUint64 atomically adds delta to *addr and returns the new value. To subtract a signed positive constant value c from x, do AddUint64(&x, ^uint64(c-1)). In particular, to decrement x, do AddUint64(&x, ^uint64(0)). Consider using the more ergonomic and less error-prone Uint64.Add instead (particularly if you target 32-bit platforms; see the bugs section).

func AddUintptr ¶

AddUintptr atomically adds delta to *addr and returns the new value. Consider using the more ergonomic and less error-prone Uintptr.Add instead.

func CompareAndSwapInt32 ¶

CompareAndSwapInt32 executes the compare-and-swap operation for an int32 value. Consider using the more ergonomic and less error-prone Int32.CompareAndSwap instead.

func CompareAndSwapInt64 ¶

CompareAndSwapInt64 executes the compare-and-swap operation for an int64 value. Consider using the more ergonomic and less error-prone Int64.CompareAndSwap instead (particularly if you target 32-bit platforms; see the bugs section).

func CompareAndSwapPointer ¶

CompareAndSwapPointer executes the compare-and-swap operation for a unsafe.Pointer value. Consider using the more ergonomic and less error-prone Pointer.CompareAndSwap instead.

func CompareAndSwapUint32 ¶

CompareAndSwapUint32 executes the compare-and-swap operation for a uint32 value. Consider using the more ergonomic and less error-prone Uint32.CompareAndSwap instead.

func CompareAndSwapUint64 ¶

CompareAndSwapUint64 executes the compare-and-swap operation for a uint64 value. Consider using the more ergonomic and less error-prone Uint64.CompareAndSwap instead (particularly if you target 32-bit platforms; see the bugs section).

func CompareAndSwapUintptr ¶

CompareAndSwapUintptr executes the compare-and-swap operation for a uintptr value. Consider using the more ergonomic and less error-prone Uintptr.CompareAndSwap instead.

func LoadInt32 ¶

LoadInt32 atomically loads *addr. Consider using the more ergonomic and less error-prone Int32.Load instead.

func LoadInt64 ¶

LoadInt64 atomically loads *addr. Consider using the more ergonomic and less error-prone Int64.Load instead (particularly if you target 32-bit platforms; see the bugs section).

func LoadPointer ¶

LoadPointer atomically loads *addr. Consider using the more ergonomic and less error-prone Pointer.Load instead.

func LoadUint32 ¶

LoadUint32 atomically loads *addr. Consider using the more ergonomic and less error-prone Uint32.Load instead.

func LoadUint64 ¶

LoadUint64 atomically loads *addr. Consider using the more ergonomic and less error-prone Uint64.Load instead (particularly if you target 32-bit platforms; see the bugs section).

func LoadUintptr ¶

LoadUintptr atomically loads *addr. Consider using the more ergonomic and less error-prone Uintptr.Load instead.

func StoreInt32 ¶

StoreInt32 atomically stores val into *addr. Consider using the more ergonomic and less error-prone Int32.Store instead.

func StoreInt64 ¶

StoreInt64 atomically stores val into *addr. Consider using the more ergonomic and less error-prone Int64.Store instead (particularly if you target 32-bit platforms; see the bugs section).

func StorePointer ¶

StorePointer atomically stores val into *addr. Consider using the more ergonomic and less error-prone Pointer.Store instead.

func StoreUint32 ¶

StoreUint32 atomically stores val into *addr. Consider using the more ergonomic and less error-prone Uint32.Store instead.

func StoreUint64 ¶

StoreUint64 atomically stores val into *addr. Consider using the more ergonomic and less error-prone Uint64.Store instead (particularly if you target 32-bit platforms; see the bugs section).

func StoreUintptr ¶

StoreUintptr atomically stores val into *addr. Consider using the more ergonomic and less error-prone Uintptr.Store instead.

func SwapInt32 ¶ added in go1.2

SwapInt32 atomically stores new into *addr and returns the previous *addr value. Consider using the more ergonomic and less error-prone Int32.Swap instead.

func SwapInt64 ¶ added in go1.2

SwapInt64 atomically stores new into *addr and returns the previous *addr value. Consider using the more ergonomic and less error-prone Int64.Swap instead (particularly if you target 32-bit platforms; see the bugs section).

func SwapPointer ¶ added in go1.2

SwapPointer atomically stores new into *addr and returns the previous *addr value. Consider using the more ergonomic and less error-prone Pointer.Swap instead.

func SwapUint32 ¶ added in go1.2

SwapUint32 atomically stores new into *addr and returns the previous *addr value. Consider using the more ergonomic and less error-prone Uint32.Swap instead.

func SwapUint64 ¶ added in go1.2

SwapUint64 atomically stores new into *addr and returns the previous *addr value. Consider using the more ergonomic and less error-prone Uint64.Swap instead (particularly if you target 32-bit platforms; see the bugs section).

func SwapUintptr ¶ added in go1.2

SwapUintptr atomically stores new into *addr and returns the previous *addr value. Consider using the more ergonomic and less error-prone Uintptr.Swap instead.

type Bool ¶ added in go1.19

A Bool is an atomic boolean value. The zero value is false.

func (*Bool) CompareAndSwap ¶ added in go1.19

CompareAndSwap executes the compare-and-swap operation for the boolean value x.

func (*Bool) Load ¶ added in go1.19

Load atomically loads and returns the value stored in x.

func (*Bool) Store ¶ added in go1.19

Store atomically stores val into x.

func (*Bool) Swap ¶ added in go1.19

Swap atomically stores new into x and returns the previous value.

type Int32 ¶ added in go1.19

An Int32 is an atomic int32. The zero value is zero.

func (*Int32) Add ¶ added in go1.19

Add atomically adds delta to x and returns the new value.

func (*Int32) CompareAndSwap ¶ added in go1.19

CompareAndSwap executes the compare-and-swap operation for x.

func (*Int32) Load ¶ added in go1.19

Func (*int32) store ¶ added in go1.19, func (*int32) swap ¶ added in go1.19, type int64 ¶ added in go1.19.

An Int64 is an atomic int64. The zero value is zero.

func (*Int64) Add ¶ added in go1.19

Func (*int64) compareandswap ¶ added in go1.19, func (*int64) load ¶ added in go1.19, func (*int64) store ¶ added in go1.19, func (*int64) swap ¶ added in go1.19, type pointer ¶ added in go1.19.

A Pointer is an atomic pointer of type *T. The zero value is a nil *T.

func (*Pointer[T]) CompareAndSwap ¶ added in go1.19

Func (*pointer[t]) load ¶ added in go1.19, func (*pointer[t]) store ¶ added in go1.19, func (*pointer[t]) swap ¶ added in go1.19, type uint32 ¶ added in go1.19.

A Uint32 is an atomic uint32. The zero value is zero.

func (*Uint32) Add ¶ added in go1.19

Func (*uint32) compareandswap ¶ added in go1.19, func (*uint32) load ¶ added in go1.19, func (*uint32) store ¶ added in go1.19, func (*uint32) swap ¶ added in go1.19, type uint64 ¶ added in go1.19.

A Uint64 is an atomic uint64. The zero value is zero.

func (*Uint64) Add ¶ added in go1.19

Func (*uint64) compareandswap ¶ added in go1.19, func (*uint64) load ¶ added in go1.19, func (*uint64) store ¶ added in go1.19, func (*uint64) swap ¶ added in go1.19, type uintptr ¶ added in go1.19.

A Uintptr is an atomic uintptr. The zero value is zero.

func (*Uintptr) Add ¶ added in go1.19

Func (*uintptr) compareandswap ¶ added in go1.19, func (*uintptr) load ¶ added in go1.19, func (*uintptr) store ¶ added in go1.19, func (*uintptr) swap ¶ added in go1.19, type value ¶ added in go1.4.

A Value provides an atomic load and store of a consistently typed value. The zero value for a Value returns nil from Load. Once Store has been called, a Value must not be copied.

A Value must not be copied after first use.

The following example shows how to use Value for periodic program config updates and propagation of the changes to worker goroutines.

The following example shows how to maintain a scalable frequently read, but infrequently updated data structure using copy-on-write idiom.

func (*Value) CompareAndSwap ¶ added in go1.17

CompareAndSwap executes the compare-and-swap operation for the Value.

All calls to CompareAndSwap for a given Value must use values of the same concrete type. CompareAndSwap of an inconsistent type panics, as does CompareAndSwap(old, nil).

func (*Value) Load ¶ added in go1.4

Load returns the value set by the most recent Store. It returns nil if there has been no call to Store for this Value.

func (*Value) Store ¶ added in go1.4

Store sets the value of the Value v to val. All calls to Store for a given Value must use values of the same concrete type. Store of an inconsistent type panics, as does Store(nil).

func (*Value) Swap ¶ added in go1.17

Swap stores new into Value and returns the previous value. It returns nil if the Value is empty.

All calls to Swap for a given Value must use values of the same concrete type. Swap of an inconsistent type panics, as does Swap(nil).

On 386, the 64-bit functions use instructions unavailable before the Pentium MMX.

On non-Linux ARM, the 64-bit functions use instructions unavailable before the ARMv6k core.

On ARM, 386, and 32-bit MIPS, it is the caller's responsibility to arrange for 64-bit alignment of 64-bit words accessed atomically via the primitive atomic functions (types Int64 and Uint64 are automatically aligned). The first word in an allocated struct, array, or slice; in a global variable; or in a local variable (because the subject of all atomic operations will escape to the heap) can be relied upon to be 64-bit aligned.

Source Files ¶

Keyboard shortcuts.

Ensuring Concurrency Safety with Atomic Operations in Golang

Table of contents.

In many backend services, configuration files or dictionary data need to be loaded dynamically. So when accessing these configurations or dictionaries, it is necessary to add locks to these data to ensure the security of concurrent reads and writes. Normally, read and write locks are required. Here’s an example of a read/write lock.

Read/Write Locks to Load Data

Using read/write locks ensures that access to data does not result in a race to state.

Dynamic data replacement using atomic operations

One characteristic of this type of business requirement is that reads are very frequent, but updates to the data will be relatively infrequent. We can replace the read and write locks with the following method.

Using atomic operations ensures that when concurrent reads and writes are performed, the new map is not acquired by the previous read operation when the data is updated, thus ensuring concurrent security.

Performance Test

Here is a performance test where ConfigV2 is using atomic operations to replace the data of map.

The difference between the two is 40 times, and the results are as follows:

In some kinds of business where there are many reads and few writes, atomic operations can be used instead of read/write locks to ensure concurrency security.
The reason for the higher performance of atomic operations may be: read-write locks require one more atomic operation to be added. (To be verified)

Package atomic

Package atomic provides low-level atomic memory primitives useful for implementing synchronization algorithms.

The swap operation, implemented by the SwapT functions, is the atomic equivalent of:

The compare-and-swap operation, implemented by the CompareAndSwapT functions, is the atomic equivalent of:

The add operation, implemented by the AddT functions, is the atomic equivalent of:

The load and store operations, implemented by the LoadT and StoreT functions, are the atomic equivalents of "return *addr" and "*addr = val".

Package files

doc.go value.go

func AddInt32 ¶

AddInt32 atomically adds delta to *addr and returns the new value.

func AddInt64 ¶

AddInt64 atomically adds delta to *addr and returns the new value.

func AddUint32 ¶

func AddUint64 ¶

func AddUintptr ¶

AddUintptr atomically adds delta to *addr and returns the new value.

func CompareAndSwapInt32 ¶

CompareAndSwapInt32 executes the compare-and-swap operation for an int32 value.

func CompareAndSwapInt64 ¶

CompareAndSwapInt64 executes the compare-and-swap operation for an int64 value.

func CompareAndSwapPointer ¶

CompareAndSwapPointer executes the compare-and-swap operation for a unsafe.Pointer value.

func CompareAndSwapUint32 ¶

CompareAndSwapUint32 executes the compare-and-swap operation for a uint32 value.

func CompareAndSwapUint64 ¶

CompareAndSwapUint64 executes the compare-and-swap operation for a uint64 value.

func CompareAndSwapUintptr ¶

CompareAndSwapUintptr executes the compare-and-swap operation for a uintptr value.

func LoadInt32 ¶

LoadInt32 atomically loads *addr.

func LoadInt64 ¶

LoadInt64 atomically loads *addr.

func LoadPointer ¶

LoadPointer atomically loads *addr.

func LoadUint32 ¶

LoadUint32 atomically loads *addr.

func LoadUint64 ¶

LoadUint64 atomically loads *addr.

func LoadUintptr ¶

LoadUintptr atomically loads *addr.

func StoreInt32 ¶

StoreInt32 atomically stores val into *addr.

func StoreInt64 ¶

StoreInt64 atomically stores val into *addr.

func StorePointer ¶

StorePointer atomically stores val into *addr.

func StoreUint32 ¶

StoreUint32 atomically stores val into *addr.

func StoreUint64 ¶

StoreUint64 atomically stores val into *addr.

func StoreUintptr ¶

StoreUintptr atomically stores val into *addr.

func SwapInt32 ¶ 1.2

SwapInt32 atomically stores new into *addr and returns the previous *addr value.

func SwapInt64 ¶ 1.2

SwapInt64 atomically stores new into *addr and returns the previous *addr value.

func SwapPointer ¶ 1.2

SwapPointer atomically stores new into *addr and returns the previous *addr value.

func SwapUint32 ¶ 1.2

SwapUint32 atomically stores new into *addr and returns the previous *addr value.

func SwapUint64 ¶ 1.2

SwapUint64 atomically stores new into *addr and returns the previous *addr value.

func SwapUintptr ¶ 1.2

SwapUintptr atomically stores new into *addr and returns the previous *addr value.

type Value ¶ 1.4

A Value provides an atomic load and store of a consistently typed value. The zero value for a Value returns nil from Load. Once Store has been called, a Value must not be copied.

A Value must not be copied after first use.

The following example shows how to use Value for periodic program config updates and propagation of the changes to worker goroutines.

The following example shows how to maintain a scalable frequently read, but infrequently updated data structure using copy-on-write idiom.

func (*Value) CompareAndSwap ¶ 1.17

CompareAndSwap executes the compare-and-swap operation for the Value.

All calls to CompareAndSwap for a given Value must use values of the same concrete type. CompareAndSwap of an inconsistent type panics, as does CompareAndSwap(old, nil).

func (*Value) Load ¶ 1.4

Load returns the value set by the most recent Store. It returns nil if there has been no call to Store for this Value.

func (*Value) Store ¶ 1.4

Store sets the value of the Value to x. All calls to Store for a given Value must use values of the same concrete type. Store of an inconsistent type panics, as does Store(nil).

func (*Value) Swap ¶ 1.17

Swap stores new into Value and returns the previous value. It returns nil if the Value is empty.

All calls to Swap for a given Value must use values of the same concrete type. Swap of an inconsistent type panics, as does Swap(nil).

On 386, the 64-bit functions use instructions unavailable before the Pentium MMX.

On non-Linux ARM, the 64-bit functions use instructions unavailable before the ARMv6k core.

On ARM, 386, and 32-bit MIPS, it is the caller's responsibility to arrange for 64-bit alignment of 64-bit words accessed atomically. The first word in a variable or in an allocated struct, array, or slice can be relied upon to be 64-bit aligned.

go-language.org

Documentation License: Creative Commons Attribution 3.0 License | Code License: BSD-3-Clause

Data Types in Go
Go Keywords
Go Control Flow
Go Functions
GoLang Structures
GoLang Arrays
GoLang Strings
GoLang Pointers
GoLang Interface
GoLang Concurrency
atomic.Store() Function in Golang With Examples
atomic.AddUintptr() Function in Golang With Examples
atomic.StoreInt32() Function in Golang With Examples
atomic.AddUint32() Function in Golang With Examples
atomic.LoadUintptr() Function in Golang With Examples
atomic.AddInt64() Function in Golang With Examples
atomic.SwapUint64() Function in Golang With Examples
atomic.SwapUint32() Function in Golang With Examples
atomic.SwapInt64() Function in Golang With Examples
atomic.CompareAndSwapUint64() Function in Golang With Examples
atomic.AddInt32() Function in Golang With Examples
atomic.SwapInt32() Function in Golang With Examples
atomic.CompareAndSwapPointer() Function in Golang With Examples
atomic.StoreUintptr() Function in Golang With Examples
atomic.LoadUint64() Function in Golang With Examples
atomic.SwapUintptr() Function in Golang With Examples
atomic.CompareAndSwapInt64() Function in Golang With Examples
atomic.Load() Function in Golang With Examples
atomic.StoreInt64() Function in Golang With Examples

atomic.StorePointer() Function in Golang With Examples

In Go language, atomic packages supply lower-level atomic memory that is helpful is implementing synchronization algorithms. The StorePointer() function in Go language is used to atomically store val into *addr . This function is defined under the atomic package. Here, you need to import the “sync/atomic” package in order to use these functions.

Here, addr indicates address.

Note: (*unsafe.Pointer) is the pointer to a unsafe.Pointer value. And unsafe.Pointer type is helpful in enabling transitions between arbitrary types and builtin uintptr type. Moreover, unsafe is a package that is helpful in type safety of Go programs.

Return Value: It stores the val into *addr and then can be returned when required.

Here, the value unsafe.Pointer is stored in *addr that’s why above code returns the stated output.

Here, the stated unsafe.Pointer val is stored and the address of the stored val is returned here. Moreover, the address can be different at different run times.

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COMMENTS

Is assigning a pointer atomic in Go?
The latter property is called visibility. The answer to the former, as of right now is yes, assigning (loading/storing) a pointer is atomic in Golang, this lies in the updated Go memory model. Otherwise, a read r of a memory location x that is not larger than a machine word must observe some write w such that r does not happen before w and ...
Is variable assignment atomic in go?
3. Assignment is not atomic, which is implied by the first sentence in the quoted documentation, and reinforced through the document as the conditions on observability are described. If that is unsatisfactory, I suggest you raise an issue with the go project for clarification in the documentation. - JimB.
Is assigning a pointer atomic in go · Issue #38667 · golang/go
More generally, pointer assignment is atomic, but you need more than that to make an example like yours work. The Go project does not use the issue tracker for questions. Please use a forum for this discussion.
Atomic Pointers in Go 1.19
In Obj-C, atomic properties will ensure operations are performed one after another, to prevent threads from accessing a memory address at the same time. Since Go is multithreaded, it supports atomic operations as well. Go 1.19 introduces new atomic types. My favorite addition is atomic.Pointer , it provides a sleek alternative to atomic.Value .
Understanding Golang's Atomic Package and Mutexes
The sync/atomic package provides low-level atomic memory primitives which can be used to modify values without the fear of race conditions. Key features of the atomic package: Atomic Operations: These functions allow operations on integers and pointers to be performed atomically. For example, atomic.AddInt64 adds an integer to an int64 value ...
How to use Atomic Pointers in Golang 1.19
In Obj-C, atomic properties will ensure operations are performed one after another to prevent threads from accessing a memory address simultaneously. Since Go is multithreaded, it supports atomic operations as well. Golang 1.19 introduces new atomic types. My favorite addition is atomic.Pointer , it provides a sleek alternative to atomic.Value ...
Atomic Operations in Golang
The atomic operations, on the other hand, are implemented at the hardware level. That means when we create a shared atomic variable and use multiple goroutines to update its value it will be updated correctly. Importing Golang atomic package. To use the atomic functions we need to import the sync/atomic package.
Understanding Atomic Counters
Photo by Brooke Cagle on Unsplash. G o, also known as Golang, is a powerful language with built-in features that make it ideal for concurrent programming. One of the primary mechanisms for managing state in Go is through communication over channels, as seen with worker pools.However, there are other efficient options available, one of which is using the sync/atomic package for atomic counters ...
atomic package
The following example shows how to maintain a scalable frequently read, but infrequently updated data structure using copy-on-write idiom. package main import ( "sync" "sync/atomic" ) func main() { type Map map[string]string var m atomic.Value m.Store(make(Map)) var mu sync.Mutex // used only by writers // read function can be used to read the data without further synchronization read := func ...
Is assigning a map atomic in go
Hi, @SmallSmartMouse, No, map assignment is not atomic. Also, your reassignment of the global data map with the temp one you created is not atomic. If your idea is to initialize a map and then store it into a global variable where it will be considered read-only, you can do that with the sync/atomic package and some pointer hackery: https ...
Ensuring Concurrency Safety with Atomic Operations in Golang
In some kinds of business where there are many reads and few writes, atomic operations can be used instead of read/write locks to ensure concurrency security. The reason for the higher performance of atomic operations may be: read-write locks require one more atomic operation to be added. (To be verified) golang.
Atomic pointer in Golang 1.19 and dependency injection
Prior to Golang 1.19, the typical solution was using the sync.Mutex. It works, but complicated. Atomic pointer. Golang 1.18 introduced generics. Its only a possibility, because Golang keeps the backward compatibility of the standard library. Introducing a new function or struct with generics is possible, like sync/atomic.Pointer, see the ...
Mastering Pointers in GoLang: Tips and Tricks for Efficient Code
To declare a pointer in GoLang, you use the * symbol before the variable name. For example, let's declare a variable x and a pointer p to it: var x int = 10. var p *int = &x. In this code, we declare an integer variable x and set its value to 10. We then declare a pointer p to x using the & operator.
The benefits of Atomic Pointers in Go 1.19 : r/golang
Some remarks: "Doing things one at the time" is not really the definition of atomic. Also, Go does not always create a new array when append is called. Only when the append operation pushes the capacity.
atomic
Package atomic provides low-level atomic memory primitives useful for implementing synchronization algorithms. These functions require great care to be used correctly. Except for special, low-level applications, synchronization is better done with channels or the facilities of the sync package. Share memory by communicating; don't communicate ...
Atomic Variable in Golang
Atomic Variable in Golang. In Go language, Atomic Variables are utilized in order to control state. Here, the "sync/atomic" package must be used to use these variables. Moreover, it also prevents race conditions which allows two or more Goroutines to access identical sources. The Atomic counters are available for several goroutines.
A Tour of Go
Pointers. Go has pointers. A pointer holds the memory address of a value. The type *T is a pointer to a T value. Its zero value is nil.. var p *int. The & operator generates a pointer to its operand.. i := 42 p = &i. The * operator denotes the pointer's underlying value.. fmt.Println(*p) // read i through the pointer p *p = 21 // set i through the pointer p
How to use Load and Store of atomic in golang
Golang: when there's only one writer change the value using atomic.StoreInt32, is it necessary to use atomic.LoadInt32 in the multiple readers? 1 golang sync/atomic package?
atomic.StorePointer() Function in Golang With Examples
The StorePointer () function in Go language is used to atomically store val into *addr. This function is defined under the atomic package. Here, you need to import the "sync/atomic" package in order to use these functions. Syntax: Here, addr indicates address. Note: (*unsafe.Pointer) is the pointer to a unsafe.Pointer value.
Golang: Assigning a value to struct member that is a pointer
Why is it an error? Because a pointer only points. It doesn't create anything to point AT. You need to do that. How to set it to false? This all depends on WHY you made it a pointer. Is every copy of this supposed to point to the same bool? Then it should be allocated some space in a creation function.