What is a race condition?
A race condition is an undesirable situation that occurs when a device or system attempts to perform two or more operations at the same time, but because of the nature of the device or system, the operations must be done in the proper sequence to be done correctly.
There are a few types of race conditions. Two categories that define the impact of the race condition on a system are referred to as critical and noncritical:
A critical race condition will cause the end state of the device, system or program to change. For example, if flipping two light switches connected to a common light at the same time blows the circuit, it is considered a critical race condition. In software, a critical race condition is when a situation results in a bug with unpredictable or undefined behavior.
A noncritical race condition does not directly affect the end state of the system, device or program. In the light example, if the light is off and flipping both switches simultaneously turns the light on and has the same effect as flipping one switch, then it is a noncritical race condition. In software, a noncritical race condition does not result in a bug.
Critical and noncritical race conditions aren't limited to electronics or programming. They can occur in many types of systems where race conditions happen.
In programming, two main types of race conditions occur in a critical section of code, which is a section of code executed by multiple threads. When multiple threads try to read a variable and then each acts on it, one of the following situations can occur:
Read-modify-write= This kind of race condition happens when two processes read a value in a program and write back a new value. It often causes a software bug. Like the example above, the expectation is that the two processes will happen sequentially -- the first process produces its value and then the second process reads that value and returns a different one.
Check-then-act= This race condition happens when two processes check a value on which they will take each take an external action. The processes both check the value, but only one process can take the value with it. The later-occurring process will read the value as null. This results in a potentially out-of-date or unavailable observation being used to determine what the program will do next. For example, if a map application runs two processes simultaneously that require the same location data, one will take the value first so the other can't use it. The later process reads the data as null.
Examples of Race Condition:
Example 1: Tube Light ON and OFF
The Race Condition usually occurs at the case of Tube Light which has multiple switches. This Tube Light with multiple switches is the biggest example for the Race Condition which has occurred in Operating Systems.
Preventing race conditions is particularly important because hackers can take advantage of race-condition vulnerabilities to gain unauthorized access to networks. One notable example of a race condition-based exploit is called Dirty Cow, which exploits a flaw in a Linux kernel's memory subsystem to create a race condition where the attacker gains write privileges for read-only memory mappings.
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