操作系统并发性：互斥和同步总结.ppt

* Processes Accessing Shared Data Protected by a Semaphore * Producer/Consumer Problem One or more producers are generating data and placing these in a buffer A single consumer is taking items out of the buffer one at time Only one producer or consumer may access the buffer at any one time …. Producer Consumer Buffer Pool * Producer/Consumer Problem #define N 100 semaphore mutex = 1; semaphore empty = N; semaphore full = 0; void producer(void) { int item; while(true){ produce_item(Item); semWait(empty); semWait(mutex); enter_item(item); semSignal(mutex); semSignal(full); } } void consumer(void) { int item; while(true){ semWait(full); semWait(mutex); remove_item(item); semSignal(mutex); semSignal(empty) consume_item(item); } } * Producer/Consumer Problem #define N 100 semaphore mutex = 1; semaphore empty = N; semaphore full = 0; void producer(void) { int item; while(true){ produce_item(Item); semWait(mutex); semWait(empty); enter_item(item); semSignal(mutex); semSignal(full); } } void consumer(void) { int item; while(true){ semWait(full); semWait(mutex); remove_item(item); semSignal(mutex); semSignal(empty) consume_item(item); } } * Monitors(管程) Monitor is a software module consisting of one or more procedures, an initialization sequence, and local data Chief characteristics Local data variables are accessible only by the monitor’s procedures and not by any external procedure Process enters monitor by invoking one of its procedures Only one process may be executing in the monitor at a time * Condition Variables Condition variable are a special data type in monitors, which are operated on by two operations: cwait(c): suspend execution of the calling process on condition c. The monitor is now ava