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What is reentrant code and its significance in memory management?
Wiki User
∙ 10y ago
In operating systems and other multithreaded, event-driven, or low-level software, it is possible to have event-handling or interrupt-handling code that is called every time an event or interrupt is triggered by hardware or software. If an event triggers a call to the handler, then the code will context switch to "enter" that method. Once in the method, suppose that it accesses a set of static structures in memory, so that they can be modified (like a counter or a routine that reads and updates the data). Now, suppose that another thread or process triggers an event to call the same method. This will enter the same handler method at the same time (a reentrant block of code). Well, while the first method is still accessing the static memory location, the second thread/process will be entering the same method to do the same thing, and they will attempt to modify the same area of memory at the same time. This is called a race condition. In order to prevent this from happening, memory management in the OS kernel should "lock" the memory location so that no other processes can overwrite that memory at the same time. They will encounter the lock and will either wait until the locked memory has been unlocked by the first routine, or they will exit. Typically, if locks are not accounted for, and two threads are dependent upon each other, a deadlock condition can also be reached, which freezes the system.
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∙ 10y ago
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By knowing how to code & memory management.
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