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Examples/conditions/README.md

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+# Producer/Consumer with condition variable examples
+
+CS3841 examples for producer/consumer that motivate the need for condition variables
+
+* prod\_con1.c - Producer and consumer with unlimited sized buffer  
+Works with a single semaphore to count full slots when only a single producer and consumer is used
+
+* prod\_con2.c - Producer and consumer with unlimited sized buffer  
+Shows a problem that can arise when multiple consumers are consuming elements from the shared space at the same time  
+With no controlled access between consumers, the number of elements in the shared space become incorrect
+
+* prod\_con3.c - Producer and consumer with unlimited sized buffer  
+Fixes the problem when multiple producers and consumers modify a shared space by using a mutex lock to prevent threads from modifying the space at the same time
+
+* prod\_con4.c - Producer and consumer with unlimited sized buffer  
+Shows a problem that can arise when a consumer wants to consume multiple items from the shared space.  Since a mutex lock is used to lock out other threads, it is possible for a consumer to remove elements from an empty shared space
+
+* prod\_con5.c - Producer and consumer with unlimited sized buffer  
+An attempt to fix the problem of a consumer removing from an empty shared space when more than one item is to be consumed by waiting in a while loop until enough elements are in the space  
+Unfortunately causes deadlock since the consumer is holding the the mutex lock while waiting for more items
+
+* prod\_con6.c - Producer and consumer with unlimited sized buffer  
+An attempt to fix the problem of a consumer removing from an empty shared space when more than one item is to be consumed by waiting in a while loop until enough elements are in the space.  
+Attemps to fix the deadlock provlem in prod\_cons5.c by releasing the lock  
+Unfortunately the consumer releasing the lock in the while loop causes undefined behavior
+
+* prod\_con7.c - Producer and consumer with unlimited sized buffer  
+An attempt to fix the problem of a consumer removing from an empty shared space when more than one item is to be consumed by releasing the lock on the shared space and then waiting on a semaphore until there are more items.  
+Unfortunately, there is know way for the consumer to get back into the "head of the line" after more items are produced.  Another consumer can skip ahead
+
+* prod\_con\_cond1.c - Producer and consumer with unlimited sized buffer  
+Uses a condition variable to ensure proper order of the consumers when they wait for more items to be consumed  
+Unfortunately, using a single condition variable without additional mutual exculsion does not maintain the consumers order in line
+
+* prod\_con\_cond2.c - Producer and consumer with unlimited sized buffer  
+Uses a condition variable to ensure proper order of the consumers when they wait for more items to be consumed  
+Also uses a mutex to control the ordering of consumers  
+This example provides correct behavior when there are multiple producers and multiple consumers and each consumer orders multiple items.