{"id":96138,"date":"2020-10-08T19:42:26","date_gmt":"2020-10-08T17:42:26","guid":{"rendered":"https:\/\/prohoster.info\/blog\/administrirovanie\/znakomimsya-s-semaforami-v-linux"},"modified":"2020-10-08T19:42:26","modified_gmt":"2020-10-08T17:42:26","slug":"znakomimsya-s-semaforami-v-linux","status":"publish","type":"post","link":"https:\/\/prohoster.info\/hu\/blog\/administrirovanie\/znakomimsya-s-semaforami-v-linux","title":{"rendered":"Ismerked\u00e9s a szemin\u00e1risokkal a Linuxban","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"<p><b><i>A cikk ford\u00edt\u00e1sa a kurzus megkezd\u00e9se el\u0151tt k\u00e9sz\u00fclt <noindex><a rel=\"nofollow\" href=\"https:\/\/otus.pw\/kRX0\/\">\u00abAdministrator Linux.Basic\u00bb<\/a><\/noindex>.<\/p>\n<p><img decoding=\"async\" alt=\"Ismerked\u00e9s a szemin\u00e1risokkal a Linuxban\" src=\"\/wp-content\/uploads\/2020\/10\/93604a8804db099834e873de072cbfc9.jpg\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\n<\/i><\/b><\/p>\n<p>A szemafor olyan mechanizmus, amely lehet\u0151v\u00e9 teszi, hogy a verseng\u0151 folyamatok \u00e9s sz\u00e1lak k\u00f6z\u00f6s er\u0151forr\u00e1sokkal dolgozzanak, \u00e9s seg\u00edt megoldani a k\u00fcl\u00f6nf\u00e9le szinkroniz\u00e1ci\u00f3s probl\u00e9m\u00e1kat, mint p\u00e9ld\u00e1ul a versenyt, holtpontra (deadlock) \u00e9s a sz\u00e1lak helytelen viselked\u00e9s\u00e9t.<\/p>\n<p>Ezeknek a probl\u00e9m\u00e1knak a megold\u00e1s\u00e1ra a kernelben olyan eszk\u00f6z\u00f6k tal\u00e1lhat\u00f3k, mint a mutexek, szemaforok, jelek \u00e9s akad\u00e1lyok.<\/p>\n<p>H\u00e1romf\u00e9le szemafor l\u00e9tezik:<\/p>\n<ol>\n<li>Bin\u00e1ris szemafor (binary semaphore)<\/li>\n<li>Sz\u00e1ml\u00e1l\u00f3 szemafor (counting semaphore)<\/li>\n<li>Szemafor t\u00f6mb\u00f6k (semaphore set)<\/li>\n<\/ol>\n<p><noindex><a rel=\"nofollow\" name=\"habracut\"><\/a><\/noindex><\/p>\n<h3>IPC \u00e1llapot\u00e1nak megtekint\u00e9se<\/h3>\n<p>\nAz al\u00e1bbi parancsok seg\u00edts\u00e9g\u00e9vel inform\u00e1ci\u00f3t nyerhet a jelenlegi interprocess communication (IPC) eszk\u00f6z\u00f6k \u00e1llapot\u00e1r\u00f3l.<\/p>\n<pre><code class=\"bash\"># ipcs\n------ Shared Memory Segments --------\nkey shmid owner perms bytes nattch status\n0x00000000 65536 root 600 393216 2 dest\n0x00000000 98305 root 600 393216 2 dest\n0x00000000 131074 root 600 393216 2 dest\n0x00000000 163843 root 600 393216 2 dest\n0x00000000 196612 root 600 393216 2 dest\n0x00000000 229381 root 600 393216 2 dest\n0x00000000 262150 root 600 393216 2 dest\n0x00000000 294919 root 600 393216 2 dest\n0x00000000 327688 root 600 393216 2 dest\n------ Semaphore Arrays --------\n\nkey semid owner perms nsems\n\n------ Message Queues --------\nkey msqid owner perms used-bytes messages<\/code><\/pre>\n<p><\/p>\n<h3>Akt\u00edv szemafor t\u00f6mb\u00f6k<\/h3>\n<p>\nInform\u00e1ci\u00f3 megjelen\u00edt\u00e9se az akt\u00edv szemafor t\u00f6mb\u00f6kr\u0151l.<\/p>\n<pre><code class=\"bash\"># ipcs -s\n------ Semaphore Arrays --------\nkey semid owner perms nsems<\/code><\/pre>\n<p><\/p>\n<h3>Megosztott mem\u00f3ria szegmensek<\/h3>\n<p>\nInform\u00e1ci\u00f3 megjelen\u00edt\u00e9se az akt\u00edv megosztott mem\u00f3ria szegmensekr\u0151l.<\/p>\n<pre><code class=\"bash\"># ipcs -m\n------ Shared Memory Segments --------\nkey shmid owner perms bytes nattch status\n0x00000000 65536 root 600 393216 2 dest\n0x00000000 98305 root 600 393216 2 dest<\/code><\/pre>\n<p><\/p>\n<h3>Korl\u00e1tok<\/h3>\n<p>\nA parancs <code>ipcs -l<\/code> megjelen\u00edti a megosztott mem\u00f3ria, szemaforok \u00e9s \u00fczenetek korl\u00e1tait.<\/p>\n<pre><code class=\"bash\"># ipcs -l\n------ Shared Memory Limits --------\nmax number of segments = 4096\nmax seg size (kbytes) = 4194303\nmax total shared memory (kbytes) = 1073741824\nmin seg size (bytes) = 1\n\n------ Semaphore Limits --------\nmax number of arrays = 128\nmax semaphores per array = 250\nmax semaphores system wide = 32000\nmax ops per semop call = 32\nsemaphore max value = 32767\n\n------ Messages: Limits --------\nmax queues system wide = 16\nmax size of message (bytes) = 65536\ndefault max size of queue (bytes) = 65536<\/code><\/pre>\n<p><\/p>\n<h3>Megosztott mem\u00f3ria<\/h3>\n<p>\nAz al\u00e1bbi parancs megjelen\u00edti a megosztott mem\u00f3ri\u00e1t.<\/p>\n<pre><code class=\"bash\"># ipcs -m\n------ Shared Memory Segments --------\nkey shmid owner perms bytes nattch status\n0x00000000 65536 root 600 393216 2 dest\n0x00000000 98305 root 600 393216 2 dest\n0x00000000 131074 root 600 393216 2 dest\n0x00000000 163843 root 600 393216 2 dest\n0x00000000 196612 root 600 393216 2 dest\n0x00000000 229381 root 600 393216 2 dest\n0x00000000 262150 root 600 393216 2 dest\n0x00000000 294919 root 600 393216 2 dest\n0x00000000 327688 root 600 393216 2 dest<\/code><\/pre>\n<p><\/p>\n<h3>Er\u0151forr\u00e1sok k\u00e9sz\u00edt\u0151i<\/h3>\n<p>\nA parancs megjelen\u00edti az er\u0151forr\u00e1s tulajdonos\u00e1t \u00e9s l\u00e9trehoz\u00f3j\u00e1nak felhaszn\u00e1l\u00f3j\u00e1t \u00e9s csoportj\u00e1t.<\/p>\n<pre><code class=\"bash\"># ipcs -m -c\n\n------ Shared Memory Segment Creators\/Owners --------\nshmid perms cuid cgid uid gid\n65536 600 root root root root\n98305 600 root root root root\n131074 600 root root root root\n163843 600 root root root root\n196612 600 root root root root\n229381 600 root root root root\n262150 600 root root root root\n294919 600 root root root root\n327688 600 root root root root<\/code><\/pre>\n<p><\/p>\n<h3>IPC eszk\u00f6z\u00f6k haszn\u00e1lata<\/h3>\n<p>\nAz al\u00e1bbi p\u00e9lda param\u00e9tere <code>-u<\/code> megjelen\u00edti az \u00f6sszes IPC eszk\u00f6z haszn\u00e1lat\u00e1nak \u00f6sszefoglal\u00f3j\u00e1t.<\/p>\n<pre><code class=\"bash\"># ipcs -u\n\n------ Shared Memory Status --------\nsegments allocated 9\npages allocated 864\npages resident 477\npages swapped 0\nSwap performance: 0 attempts 0 successes\n\n------ Semaphore Status --------\nused arrays = 0\nallocated semaphores = 0\n\n------ Messages: Status --------\nallocated queues = 0\nused headers = 0\nused space = 0 bytes<\/code><\/pre>\n<p>\nSzolg\u00e1ltat\u00e1sok le\u00e1ll\u00edt\u00e1sakor a szemaforoknak \u00e9s a megosztott mem\u00f3ria szegmenseknek is t\u00f6rl\u0151dni\u00fck kell. Ha nem t\u00f6rl\u0151dnek, ezt az ipcrm paranccsal teheti meg, az IPC-objektum azonos\u00edt\u00f3j\u00e1t \u00e1tadva.<\/p>\n<pre><code class=\"bash\"># ipcs -a\n# ipcrm -s &lt; sem id&gt;<\/code><\/pre>\n<p>\nA szemaforok korl\u00e1tait is m\u00f3dos\u00edthatja, haszn\u00e1lva <code>sysctl<\/code>.<\/p>\n<pre><code class=\"bash\"># \/sbin\/sysctl -w kernel.sem=250\n<\/code><\/pre>\n<p>\n<noindex><a rel=\"nofollow\" href=\"https:\/\/otus.pw\/kRX0\/\"><img decoding=\"async\" alt=\"Ismerked\u00e9s a szemin\u00e1risokkal a Linuxban\" src=\"\/wp-content\/uploads\/2020\/10\/e9f6606dbef02ed0dd83662ed9b40015.jpg\" style=\"display:block;margin: 0 auto;\" \/><\/a><\/noindex><br \/>\n<br \/>Forr\u00e1s: <a content=\"nofollow\" rel=\"nofollow\" href=\"https:\/\/habr.com\/ru\/company\/otus\/blog\/522418\/\">habr.com<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"<p>\u041f\u0435\u0440\u0435\u0432\u043e\u0434 \u0441\u0442\u0430\u0442\u044c\u0438 \u043f\u043e\u0434\u0433\u043e\u0442\u043e\u0432\u043b\u0435\u043d \u0432 \u043f\u0440\u0435\u0434\u0434\u0432\u0435\u0440\u0438\u0438 \u0441\u0442\u0430\u0440\u0442\u0430 \u043a\u0443\u0440\u0441\u0430 \u00abAdministrator Linux.Basic\u00bb. \u0421\u0435\u043c\u0430\u0444\u043e\u0440 \u2013 \u044d\u0442\u043e \u043c\u0435\u0445\u0430\u043d\u0438\u0437\u043c, \u043a\u043e\u0442\u043e\u0440\u044b\u0439 \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u0435\u0442 \u043a\u043e\u043d\u043a\u0443\u0440\u0438\u0440\u0443\u044e\u0449\u0438\u043c \u043f\u0440\u043e\u0446\u0435\u0441\u0441\u0430\u043c \u0438 \u043f\u043e\u0442\u043e\u043a\u0430\u043c \u0440\u0430\u0431\u043e\u0442\u0430\u0442\u044c \u0441 \u043e\u0431\u0449\u0438\u043c\u0438 \u0440\u0435\u0441\u0443\u0440\u0441\u0430\u043c\u0438 \u0438 \u043f\u043e\u043c\u043e\u0433\u0430\u0435\u0442 \u0432 \u0440\u0435\u0448\u0435\u043d\u0438\u0438 \u0440\u0430\u0437\u043b\u0438\u0447\u043d\u044b\u0445 \u043f\u0440\u043e\u0431\u043b\u0435\u043c \u0441\u0438\u043d\u0445\u0440\u043e\u043d\u0438\u0437\u0430\u0446\u0438\u0438 \u0442\u0430\u043a\u0438\u0445 \u043a\u0430\u043a \u0433\u043e\u043d\u043a\u0438, \u0434\u0435\u0434\u043b\u043e\u043a\u0438 (\u0432\u0437\u0430\u0438\u043c\u043d\u044b\u0435 \u0431\u043b\u043e\u043a\u0438\u0440\u043e\u0432\u043a\u0438) \u0438 \u043d\u0435\u043f\u0440\u0430\u0432\u0438\u043b\u044c\u043d\u043e\u0435 \u043f\u043e\u0432\u0435\u0434\u0435\u043d\u0438\u0435 \u043f\u043e\u0442\u043e\u043a\u043e\u0432. \u0414\u043b\u044f \u0440\u0435\u0448\u0435\u043d\u0438\u044f \u044d\u0442\u0438\u0445 \u043f\u0440\u043e\u0431\u043b\u0435\u043c \u0432 \u044f\u0434\u0440\u0435 \u043f\u0440\u0438\u0441\u0443\u0442\u0441\u0442\u0432\u0443\u044e\u0442 \u0442\u0430\u043a\u0438\u0435 \u0441\u0440\u0435\u0434\u0441\u0442\u0432\u0430 \u043a\u0430\u043a \u043c\u044c\u044e\u0442\u0435\u043a\u0441\u044b, \u0441\u0435\u043c\u0430\u0444\u043e\u0440\u044b, \u0441\u0438\u0433\u043d\u0430\u043b\u044b \u0438 \u0431\u0430\u0440\u044c\u0435\u0440\u044b. [&hellip;]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":96139,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[688],"tags":[],"class_list":["post-96138","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-administrirovanie"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 5.0.3 - aioseo.com -->\n\t<meta name=\"description\" content=\"\u041f\u0435\u0440\u0435\u0432\u043e\u0434 \u0441\u0442\u0430\u0442\u044c\u0438 \u043f\u043e\u0434\u0433\u043e\u0442\u043e\u0432\u043b\u0435\u043d \u0432 \u043f\u0440\u0435\u0434\u0434\u0432\u0435\u0440\u0438\u0438 \u0441\u0442\u0430\u0440\u0442\u0430 \u043a\u0443\u0440\u0441\u0430 \u00abAdministrator Linux.Basic\u00bb.\" \/>\n\t<meta name=\"robots\" content=\"max-image-preview:large\" \/>\n\t<meta name=\"author\" content=\"Yuri Gagarin\"\/>\n\t<link 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