{
"q1": {
"type": "blank",
"question": "\n\n\nIn a ____ program, there is more than one point of execution. Each ____ in\nthe process is a separate stream of execution, but still shares the same\naddress space and thus can access the same data.\n\n\n"
},
"q2": {
"type": "multiple",
"question": "\n\n\nWhich of the following are true statements about threads (choose all that apply)?\n\n\n",
"responses": {
"registers": "Threads share the same set of registers and program counters.",
"tcb": "The state of each thread is stored in a thread control block.",
"address": "All threads within a process share the same code, data, and heap, but not stack.",
"onethread": "Only one thread per process is allowed to be executed at a time."
}
},
"q3": {
"type": "blank",
"question": "\n\n\nTo take advantage of modern CPUs with multiple cores, application\ndevelopers must ____ their ____ programs such that multiple threads do work\non different CPUs simultaneously. One common use of threads is to ____ I/O\nwith other activities within a program.\n\n\n"
},
"q4": {
"type": "blank",
"question": "\n\n\nWith processes, we use fork to create a new process, and\nwait to wait for the process to finish. With POSIX threads, we\nuse ____ to start a thread and ____ to wait for one to\nfinish.\n\nTo guard a critical section of code, we can use the POSIX threads library\nto utilize a lock as follows:\n\n\n\n\n____ lock = ____; // 3 & 4\n____(&lock); // 5\nx = x + 1; // Critical section\n____(&lock); // 6\n
\n\n\n\nIf we need some sort of signaling between threads, we can use a ____ in the\nfollowing format:\n\n\n\n\npthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;\n____ cond = ____; // 8 & 9\npthread_mutex_lock(&lock);\n while (ready == 0)\n ____(&cond, &lock); // 10\npthread_mutex_unlock(&lock);\n
\n\n\n\nTo perform the actual signaling, we would put the following code in\nanother thread:\n\n\n\n\npthread_mutex_lock(&lock);\nready = 1;\n____(&cond); // 11\npthread_mutex_unlock(&lock);\n
\n"
},
"q5": {
"type": "single",
"question": "\n\n\nWhat is the problem with the code in Figure 26.6?\n\n\n",
"responses": {
"deadlock": "There is a deadlock because two threads are accessing the same variable.",
"nullargs": "The threads are passed NULL arguments.",
"misspelled": "The code has misspellings (Pthread_create instead of pthread_create).",
"racecondition": "There is a race condition because the results depend on the timing execution of the code."
}
},
"q6": {
"type": "blank",
"question": "\n\n\nTo solve the problem in Figure 26.6, we either need ____ instructions which\noperate in a \"all or none\" fashion, or a set of ____ which will allow us to\nbuild multi-threaded code that in a synchronized and controlled manner.\n\n\n"
},
"q7": {
"type": "order",
"question": "\n\n\nMatch the following terms with the following definitions (pick the terms in\norder):\n\n\n\n\n\n - Arises if multiple threads attempt to update a shared resource,\n leading to a surprising (and perhaps undesirable) outcome.
\n\n - A piece of code that accesses a shared resource (usually a variable or\n data structure).
\n\n - A primitive that guarantees only a single thread has access to a\n resource.
\n\n - A program whose output varies from run to run, depending on which\n threads ran when, and thus is not deterministic.
\n\n
\n",
"responses": {
"critical": "Critical Section",
"mutex": "Mutual Exclusion",
"indeterminate": "Indeterminate",
"racecondition": "Race Condition"
}
},
"q8": {
"type": "blank",
"question": "\n\n\nIn ____ concurrency, we simply wait for something to occur; when it does,\nwe do some small amount of work based on the type of event. This\nprocessing usually happens in a simple construct known as an ____.\n\nOn a Unix system we can use either the ____ or ____ system calls to perform\nnon-blocking or ____ I/O. The advantage of the event-based approach is\nthat we don't need to deal with any locks normally found in threaded\nprograms.\n\n\n"
}
}