{"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\/pt\/blog\/administrirovanie\/znakomimsya-s-semaforami-v-linux","title":{"rendered":"Conhecendo sem\u00e1foros no Linux","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"<p><b><i>A tradu\u00e7\u00e3o do artigo foi preparada em antecipa\u00e7\u00e3o ao in\u00edcio do curso <noindex><a rel=\"nofollow\" href=\"https:\/\/otus.pw\/kRX0\/\">\u00abAdministrador Linux.Basic\u00bb<\/a><\/noindex>.<\/p>\n<p><img decoding=\"async\" alt=\"Conhecendo sem\u00e1foros no Linux\" src=\"\/wp-content\/uploads\/2020\/10\/93604a8804db099834e873de072cbfc9.jpg\" style=\"display:block;margin: 0 auto;\" \/><br \/>\n<br \/>\n<\/i><\/b><\/p>\n<p>Um sem\u00e1foro \u00e9 um mecanismo que permite que processos e threads concorrentes trabalhem com recursos compartilhados e ajuda a resolver v\u00e1rias quest\u00f5es de sincroniza\u00e7\u00e3o, como condi\u00e7\u00f5es de corrida, deadlocks (bloqueios m\u00fatuos) e comportamentos inadequados de threads.<\/p>\n<p>Para resolver essas quest\u00f5es, o n\u00facleo possui ferramentas como mutexes, sem\u00e1foros, sinais e barreiras.<\/p>\n<p>Existem tr\u00eas tipos de sem\u00e1foros:<\/p>\n<ol>\n<li>Sem\u00e1foros bin\u00e1rios (binary semaphore)<\/li>\n<li>Sem\u00e1foros contadores (counting semaphore)<\/li>\n<li>Conjuntos de sem\u00e1foros (semaphore set)<\/li>\n<\/ol>\n<p><noindex><a rel=\"nofollow\" name=\"habracut\"><\/a><\/noindex><\/p>\n<h3>Visualizando o estado do IPC<\/h3>\n<p>\nCom os comandos listados abaixo, \u00e9 poss\u00edvel obter informa\u00e7\u00f5es sobre o estado atual dos recursos de comunica\u00e7\u00e3o entre processos (inter-process communication, IPC).<\/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>Matrizes ativas de sem\u00e1foros<\/h3>\n<p>\nExibe informa\u00e7\u00f5es sobre as matrizes ativas de sem\u00e1foros.<\/p>\n<pre><code class=\"bash\"># ipcs -s\n------ Semaphore Arrays --------\nkey semid owner perms nsems<\/code><\/pre>\n<p><\/p>\n<h3>Segmentos de mem\u00f3ria compartilhada<\/h3>\n<p>\nVisualiza informa\u00e7\u00f5es sobre os segmentos ativos de mem\u00f3ria compartilhada.<\/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>Limites<\/h3>\n<p>\nTime <code>ipcs -l<\/code> exibe os limites de mem\u00f3ria compartilhada, sem\u00e1foros e mensagens.<\/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>Mem\u00f3ria compartilhada<\/h3>\n<p>\nO comando abaixo exibe a mem\u00f3ria compartilhada.<\/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>Criadores de recursos<\/h3>\n<p>\nO comando exibe o usu\u00e1rio e o grupo propriet\u00e1rio e criador do recurso.<\/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>Uso dos recursos IPC<\/h3>\n<p>\nNo exemplo abaixo, o par\u00e2metro <code>-u<\/code> exibe um resumo do uso de todos os recursos IPC.<\/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>\nAo parar os servi\u00e7os, os sem\u00e1foros e segmentos de mem\u00f3ria compartilhada tamb\u00e9m devem ser removidos. Se n\u00e3o forem removidos, isso pode ser feito com o comando ipcrm, passando o identificador do objeto IPC.<\/p>\n<pre><code class=\"bash\"># ipcs -a\n# ipcrm -s &lt; sem id&gt;<\/code><\/pre>\n<p>\nOs limites dos sem\u00e1foros tamb\u00e9m podem ser alterados usando <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=\"Conhecendo sem\u00e1foros no Linux\" src=\"\/wp-content\/uploads\/2020\/10\/e9f6606dbef02ed0dd83662ed9b40015.jpg\" style=\"display:block;margin: 0 auto;\" \/><\/a><\/noindex><br \/>\n<br \/>Fonte: <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 5.0.4 - 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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