---
title: "thread_signal()"
description: "Send a signal to a particular thread in the current process."
url: "https://wasix.org/docs/api-reference/wasix/thread_signal/"
markdown: "https://wasix.org/docs/api-reference/wasix/thread_signal.md"
---

# `thread_signal()`

Send a signal to a particular thread in the current process.

## Description

The `thread_signal()` function sends a signal to a specific thread within the current process. It takes a `Tid` as input, representing the thread identifier, and a `Signal` indicating the signal to be raised for the thread.

This function is similar to the `signal` function in POSIX, which allows sending signals to specific threads or processes.

## Syntax

```ebnf
  ;;; Sends a signal to a specific thread
  (@interface func (export "thread_signal")
    ;;; Handle of the thread to send a signal
    (param $tid $tid)
    ;;; Signal to send to the thread
    (param $signal $signal)
    (result $error (expected (error $errno)))
  )
```

## Parameters

- `ctx`: A mutable reference to the function environment.
- `tid`: The thread identifier (Tid) of the target thread to which the signal should be sent.
- `sig`: The signal to be raised for the target thread.

## Return Value

The function returns `Ok(Errno::Success)` if the operation is successful. Otherwise, it returns an appropriate `WasiError` value.

## Logging

This function is instrumented with `debug` level logging. It includes the following fields for debugging purposes:

- `tid`: The thread identifier (Tid) of the target thread.
- `sig`: The signal to be raised for the target thread.

## Note

- The `thread_signal()` function allows sending a signal to a particular thread within the current process.
- It uses the `signal_thread()` method of the current process to send the signal to the specified thread.
- This function is similar to the `signal` function in POSIX, which enables sending signals to specific threads or processes.
- After sending the signal, the function calls `WasiEnv::process_signals_and_exit()` to process any pending signals and handle process termination if necessary.
- Proper handling and interpretation of signals is important for synchronization, communication, and control between threads within an application.
- Signals provide a way to communicate specific instructions or events to threads or processes, enabling various behaviors such as termination, interruption, or custom actions.
- The `thread_signal()` function in the WASI environment allows you to send signals to individual threads, providing flexibility and control over thread-level operations.
- It’s important to note that the behavior and handling of signals may vary depending on the underlying operating system and signal implementation.
- Understanding the semantics and implications of signals in the target platform is crucial for correct and reliable signal handling in multi-threaded environments.
- The `thread_signal()` function provides a convenient and consistent way to send signals to specific threads in the WASI environment.
- Thread signals can be used for various purposes such as thread synchronization, interruption, termination, or customized thread-specific actions.
- Signal handling should be carefully designed and implemented to ensure correct and reliable behavior in multi-threaded applications.
- The `thread_signal()` function is a powerful tool for managing and controlling threads by sending signals to specific threads in the current process.

---

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