Chapter 7, Problem 30QAP

Given the contents of the heap shown on the left, show the new contents of the heap (in the right table) after a call to free(0x400b010) is executed. Your answers should be given as hex values. Note that the address grows from bottom up. Assume that the allocator uses immediate coalescing, that is, adjacent free blocks are merged immediately each time a block is freed. Address 0x400b028 0x00000012 Address 0x400b028 0x400b024 0x400b611c 0x400b024 0x400b611c 0x400b020 0x400b512c 0x400b020 0x400b512c 0x400b01c 0x00000012 0x400b01c 0x400b018 0x00000013 0x400b018 0x400b014 0x400b511c 0x400b014 0x400b511c 0x400b010 0x400b601c 0x400b010 0x400b601c 0x400b00c 0x00000013 0x400b00c 0x400b008 0x00000013 0x400b008 0x400b004 0x400b601c 0x400b004 0x400b601c 0x400b000 0x400b511c 0x400b000 0x400b511c 0x400affc 0x00000013 0x400affc

Calculate the neutral current in a 120/240-volt, single-phase system when the current inphase A is 20 amperes and the current in phase B is 40 amperes. The load is resistive.  Calculate the neutral current in a 208Y/120-volt, 3-phase, 4-wire system when thecurrent in phase A is 0, in phase B is 40, and in phase C is 60 amperes. The load isresistive

Your programming buddy notices that your code has some race conditions, and draws up the following locking mechanism: int locked = 0; void lock() { while (locked == 1) { } continue; // keep looping locked = 1; void unlock() { } locked = 0; Because the load-increment-store sequence is the critical section of your program, you place a call to lock() immediately before the i++ line, and a call to unlock() immediately after. However, running your supposedly-now-threadsafe program again, you discover that the output is still nondeterministic. Turns out your buddy's clever locking scheme doesn't do a very good job protecting the critical section after all. (Note: unlike semaphore locking and unlocking functions, lock() and unlock() DO NOT execute atomically.) C. Give an execution sequence of two threads in the lock() function that would end up with both threads holding the lock at the same time.

Calculate the neutral current in a 208Y/120-volt, 3-phase, 4-wire system when the current in phase A is 20, in phase B is 40, and in phase C is 60 amperes. The load is resistive.

I need expert to solve this,if you don't know don't attempt,also show the signal flow diagram

Suppose we alter do stuff to look as follows: void *do_stuff(void *arg attribute ((unused))) { int a; for (a = 0; a < 1000; a++) i++; return NULL; } Because the code is not optimized, there will be one load-increment-store sequence per iteration of the loop. B. For each number, tell whether or not our program could output it, and briefly explain why or why not. • 2000 • 1500 . 2 1

The following problem concerns the way virtual addresses are translated into physical addresses. Thememory is byte addressable. • Memory accesses are to 1-byte words (not 4-byte words). • Virtual addresses are 16 bits wide. • Physical addresses are 13 bits wide. •The page size is 512 bytes. • The TLB is 8-way set associative with 16 total entries. • The cache is 2-way set associative, with a 4 byte line size and 16 total lines. In the following tables, all numbers are given in hexadecimal. The contents of the TLB, the page table for the first 32 pages, and the cache are as follows: TLB Page Table 2-way Set Associative Cache Index Tag PPN Valid VPN PPN Valid VPN PPN Valid Index Tag Valid Byte 0 Byte 1 Byte 2 Byte 3 Tag Valid Byte 0 Byte 1 Byte 2 Byte 3 0 09 4 1 00 6 1 10 0 1 0 19 1 99 11 23 11 00 0 99 11 23 11 12 2 1 01 5 0 11 5 0 1 15 0 4F 22 EC 11 2F 1 55 59 OB 41 10 0 1 02 3 1 12 2 1 2 1B 1 00 02 04 08 OB 1 01 03 05 07 08 5 03 4 1 13 4 0 3 06 0 84 06 B2 9C 12 0 84 06 B2 9C 05 7 1 04…

Part II (8 points) int counter = 0; void handler(int sig) { counter++; } int main() { int i; signal(SIGCHLD, handler); for (i = 0; i < 5; i ++){ if (fork() == 0){ } } exit(0); /* wait for all children to die */ while (wait(NULL) != -1); printf("counter = %d\n", counter); return 0; } A. Does the program output the same value of counter every time we run it? Yes No B. If the answer to A is Yes, indicate the value of the counter variable. Otherwise, list all possible values of the counter variable. Answer: counter =

A useful helper function for opening a socket connection to a server was introduced in the course: int open_clientfd(char *hostname, int port) { int clientfd; struct hostent *hp; struct sockaddr_in serveraddr; if ((clientfd = socket(AF_INET, SOCK_STREAM, 0)) h_addr_list[0], (char *)&serveraddr.sin_addr.s_addr, hp->h_length); serveraddr.sin_port = htons(port); /* Establish a connection with the server */ if (connect(clientfd, (SA *) &serveraddr, sizeof(serveraddr)) < 0) return -1; return clientfd; } The problem with this function is that it is not thread safe: it uses function gethostbyname, which returns a pointer to a static variable. On the following page, reimplement open_clientfd in a thread safe way using the lock-and-copy technique. (Note 1: that the new function will take an additional input: a semaphore that will control access to the critical section so only one thread at a time can call gethostbyname and read the result stored in a static variable. Note 2: a call to malloc is…