Hands-On System Programming with Linux

Summary table – approaches to making functions thread-safe

Let's summarize the preceding points in the form of a table that tells us how to achieve the all-important goal of thread-safety for all our functions:

Approach to make a function thread-safe	Comments
Use only local variables	Naive; hard to achieve in practice.
Use global and/or static variables and protect critical sections with mutex locks	Viable but can significantly impact performance [1]
Refactor the function, making it reentrant-safe-eliminate the use of static variables in a function by using more parameters as required	Useful approach—several old foo glibc functions refactored to foo_r.
Thread local storage (TLS)	Ensures thread safety by having one copy of the variable ...