GNU Info

(libc.info)Atomic Data Access

---

Prev: Nonreentrancy Up: Defining Handlers

---

Enter node , (file) or (file)node

Atomic Data Access and Signal Handling
--------------------------------------

   Whether the data in your application concerns atoms, or mere text,
you have to be careful about the fact that access to a single datum is
not necessarily "atomic".  This means that it can take more than one
instruction to read or write a single object.  In such cases, a signal
handler might be invoked in the middle of reading or writing the object.

   There are three ways you can cope with this problem.  You can use
data types that are always accessed atomically; you can carefully
arrange that nothing untoward happens if an access is interrupted, or
you can block all signals around any access that had better not be
interrupted (Note: Blocking Signals).

Non-atomic Example

A program illustrating interrupted access.

Types

Atomic Types. Data types that guarantee no interruption.

Usage

Atomic Usage. Proving that interruption is harmless.