The std::mutex is a non-recursive mutex and therefore can’t be locked again from the same thread before getting unlocked. This can lead quite fast to a deadlock. That’s the point where std::recursive_mutex comes in place. It can be locked multiple time from the same threat without the need to unlock it first.<\/p>\n
Example – With deadlock<\/u><\/p>\n The std::mutex is a non-recursive mutex and therefore can’t be locked again from the same thread before getting unlocked. This<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"inline_featured_image":false},"categories":[63],"tags":[],"_links":{"self":[{"href":"http:\/\/www.max-sperling.bplaced.net\/index.php?rest_route=\/wp\/v2\/posts\/7861"}],"collection":[{"href":"http:\/\/www.max-sperling.bplaced.net\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.max-sperling.bplaced.net\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.max-sperling.bplaced.net\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.max-sperling.bplaced.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=7861"}],"version-history":[{"count":1,"href":"http:\/\/www.max-sperling.bplaced.net\/index.php?rest_route=\/wp\/v2\/posts\/7861\/revisions"}],"predecessor-version":[{"id":16748,"href":"http:\/\/www.max-sperling.bplaced.net\/index.php?rest_route=\/wp\/v2\/posts\/7861\/revisions\/16748"}],"wp:attachment":[{"href":"http:\/\/www.max-sperling.bplaced.net\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=7861"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.max-sperling.bplaced.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=7861"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.max-sperling.bplaced.net\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=7861"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}\r\n#include <iostream>\r\n#include <thread>\r\n#include <mutex>\r\n\r\nclass Cache\r\n{\r\npublic:\r\n Cache() : m_Mtx(), m_Val(0) {}\r\n\r\n bool update(int val) {\r\n std::lock_guard<std::mutex> lock(m_Mtx);\r\n\r\n bool updated = false;\r\n if (m_Val != val) {\r\n write(val);\r\n updated = true;\r\n std::cout << "val has been updated" << std::endl;\r\n }\r\n return updated;\r\n }\r\n\r\nprivate:\r\n void write(int val) {\r\n std::lock_guard<std::mutex> lock(m_Mtx); \/\/ 2nd lock --> deadlock\r\n m_Val = val;\r\n }\r\n\r\n std::mutex m_Mtx;\r\n int m_Val;\r\n};\r\n\r\nint main()\r\n{\r\n Cache cache;\r\n std::thread t(&Cache::update, &cache, 42);\r\n t.join();\r\n\r\n return 0;\r\n}\r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"