c - munmap anonymous shared memory in forked child -


i'd know if necessary (or advisable) unmap shared memory (using munmap) in child created via fork, if memory obtained in parent, before fork, using mmap(..., map_anonymous | map_shared,...) , unmapped in parent, wait child. know whether necessary (or advisable) close file in child, if file opened in parent (before fork, using fopen) , closed in parent after child terminates.

i thinking of using user-defined signal , signal handler in parent wait child processes, , process -- wheter parent or not -- close file , unmap memory. signal sent processes in group process, in error occurred (i not want pass return values).

actually bit more complex, want know whether need this:

void sig_handler() {     if (getpid() == getpgrp()) // parent         while (proc_count--)             wait(null); // signal has been sent child processes     // every single process this:     fclose(memory->file);     munmap(memory, size);     exit(123); }

or completely ok this:

void sig_handler() {     if (getpid() == getpgrp()) {         while (proc_count--)             wait(null);         fclose(memory->file);         munmap(memory, size);     }     exit(123); }

i have tried closing file in 1 child process; seemed have no effect in other processes -- assume fd table copied on fork. there way make shared between processes? (probably not, suspect)

any answer appreciated. thank you.

ps. there reason why can't start question greeting (eg. hello) ?

if you're going exit process, there's no point in calling munmap(). memory unmapped process when process exits.

fclose() flush buffers holding unwritten data file. in processes - parent , child. whether or not want you.

exit() implicitly flushes buffers. _exit() not flush buffers or call other exit handlers.


Comments

Post a Comment

Popular posts from this blog

python - Installing PyDev in eclipse is failed -

unable read repository @ http://pydev.sf.net/updates/content.xml. sun.security.validator.validatorexception: pkix path building failed: sun.security.provider.certpath.suncertpathbuilderexception: unable find valid certification path requested target i installing pydev in eclipse using python, doesn't install successfully. gives above error. happened? how solve error? i had error when trying install on laptop behind corporate firewall. couldn't tell setup of firewall, not sure of root cause. i got passed error installing pydev eclipse when out behind firewall. another way got around have eclipse on non-firewalled machine, install pydev eclipse, , copy whole eclipse directory non-firewalled machine firewalled machine. there better way, , way fix properly, didn't have time work out firewall doing. this on windows 7 machine (yeah know) not work *nix versions installed through package manager yum or apt.
Read more

PHP OOP-based login system -

lets building oop-based user authentication system, , incorporate following principles: direct injection, inheritance, encapsulation, polymorphism , single responsibility principle. my background in programming has relied on procedural programming, , thus, finding difficult put these practices correct use. assume have these classes: class config { public function set($key, $value); public function get($key, $default = null); } class user { public function __construct(pdo $dbh, $id = null); public function setprofile(profile $profile); } class auth { public function __construct(config $config); public function login($username, $password, $keeploggedin = true); public function isloggedin(); public function getloggedinuser(); public function logout(); public function register(array $data); } class session { public function start($sessionname = null); public function write($key, $value); public function read($key, $default =...
Read more

c# - Nested Internal Class with Readonly Hashtable throws Null ref exception.. on assignment -

in internal game class , have both a) defined nested internal gamertags class , b) defined gamertags[] _array variable. in internal gamertags class (the nested class, simplicity left out) have readonly hashtable . after initialization, still null ref exception when try assign value. i'm not changing pointer value only , need add initialization hastable? internal class gamertags { private readonly hashtable _privatereadonlyhashtable; private string _json; private string _hash; internal idictionary privatereadonlyhashtable { { return this._privatereadonlyhashtable; } } internal string hash { { this.ensurehash(); return this._hash; } } internal object this[string key] { { return this._privatereadonlyhashtable[k...
Read more