{"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\/de\/blog\/administrirovanie\/znakomimsya-s-semaforami-v-linux","title":{"rendered":"Einf\u00fchrung in Semaphore unter Linux","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"<p><b><i>Die \u00dcbersetzung des Artikels wurde im Vorfeld des Starts des Kurses vorbereitet <noindex><a rel=\"nofollow\" href=\"https:\/\/otus.pw\/kRX0\/\">\u201eAdministrator Linux.Basic\u201c<\/a><\/noindex>.<\/p>\n<p><img decoding=\"async\" alt=\"Einf\u00fchrung in Semaphore unter Linux\" src=\"\/wp-content\/uploads\/2020\/10\/93604a8804db099834e873de072cbfc9.jpg\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\n<\/i><\/b><\/p>\n<p>Ein Semaphore ist ein Mechanismus, der es konkurrierenden Prozessen und Threads erm\u00f6glicht, mit gemeinsamen Ressourcen zu arbeiten und bei der L\u00f6sung verschiedener Synchronisationsprobleme wie Race Conditions, Deadlocks (gegenseitige Sperrungen) und unerw\u00fcnschtem Verhalten von Threads hilft.<\/p>\n<p>Um diese Probleme zu l\u00f6sen, stehen im Kernel Hilfsmechanismen wie Mutexes, Semaphoren, Signale und Barrieren zur Verf\u00fcgung.<\/p>\n<p>Es gibt drei Arten von Semaphoren:<\/p>\n<ol>\n<li>Bin\u00e4re Semaphore (binary semaphore)<\/li>\n<li>Z\u00e4hlende Semaphore (counting semaphore)<\/li>\n<li>Semaphore-Arrays (semaphore set)<\/li>\n<\/ol>\n<p><noindex><a rel=\"nofollow\" name=\"habracut\"><\/a><\/noindex><\/p>\n<h3>IPC-Zustandsanzeige<\/h3>\n<p>\nMit den unten aufgef\u00fchrten Befehlen kann man Informationen \u00fcber den aktuellen Zustand der Mittel der zwischenprozesslichen Kommunikation (inter-process communication, IPC) abrufen.<\/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>Aktive Semaphore-Arrays<\/h3>\n<p>\nAnzeige von Informationen \u00fcber aktive Semaphore-Arrays.<\/p>\n<pre><code class=\"bash\"># ipcs -s\n------ Semaphore Arrays --------\nkey semid owner perms nsems<\/code><\/pre>\n<p><\/p>\n<h3>Segmente des gemeinsamen Speichers<\/h3>\n<p>\nAnzeige von Informationen \u00fcber aktive Segmente des gemeinsamen Speichers.<\/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>Grenzen<\/h3>\n<p>\nTeam <code>ipcs -l<\/code> zeigt die Grenzen des gemeinsamen Speichers, der Semaphore und der Nachrichten an.<\/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>Gemeinsamer Speicher<\/h3>\n<p>\nDer untenstehende Befehl zeigt den gemeinsamen Speicher an.<\/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>Ressourcenersteller<\/h3>\n<p>\nDer Befehl zeigt den Benutzer und die Gruppe des Eigent\u00fcmers und Erstellers der Ressource an.<\/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>Nutzung der IPC-Mittel<\/h3>\n<p>\nIm untenstehenden Beispiel zeigt der Parameter <code>-u<\/code> eine Zusammenfassung der Nutzung aller IPC-Mittel an.<\/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>\nBeim Stoppen der Dienste m\u00fcssen auch die Semaphore und die gemeinsamen Speichersegmente entfernt werden. Wenn sie nicht entfernt werden, kann dies mit dem Befehl ipcrm unter Angabe der IPC-Objekt-ID erfolgen.<\/p>\n<pre><code class=\"bash\"># ipcs -a\n# ipcrm -s &lt; sem id&gt;<\/code><\/pre>\n<p>\nDie Grenzen der Semaphore k\u00f6nnen ebenfalls ge\u00e4ndert werden, indem man <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=\"Einf\u00fchrung in Semaphore unter Linux\" src=\"\/wp-content\/uploads\/2020\/10\/e9f6606dbef02ed0dd83662ed9b40015.jpg\" style=\"display:block;margin: 0 auto;\" \/><\/a><\/noindex><br \/>\n<br \/>Quelle: <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. 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