From: Daniel Stenberg Date: Fri, 14 Apr 2023 09:34:55 +0000 (+0200) Subject: libcurl-thread.3: improved name resolver wording X-Git-Tag: curl-8_1_0~139 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=7ed010ce2192ae3e4d9663eaaa3a460f316b708b;p=thirdparty%2Fcurl.git libcurl-thread.3: improved name resolver wording And make better .SH sections Closes #10966 --- diff --git a/docs/libcurl/libcurl-thread.3 b/docs/libcurl/libcurl-thread.3 index a29c4e821d..5c189de459 100644 --- a/docs/libcurl/libcurl-thread.3 +++ b/docs/libcurl/libcurl-thread.3 @@ -30,13 +30,17 @@ libcurl is thread safe but has no internal thread synchronization. You may have to provide your own locking should you meet any of the thread safety exceptions below. -\fBHandles.\fP You must \fBnever\fP share the same handle in multiple threads. -You can pass the handles around among threads, but you must never use a single -handle from more than one thread at any given time. - -\fBShared objects.\fP You can share certain data between multiple handles by -using the share interface but you must provide your own locking and set +.SH "Handles" +You must \fBnever\fP share the same handle in multiple threads. You can pass +the handles around among threads, but you must never use a single handle from +more than one thread at any given time. +.SH "Shared objects" +You can share certain data between multiple handles by using the share +interface but you must provide your own locking and set \fIcurl_share_setopt(3)\fP CURLSHOPT_LOCKFUNC and CURLSHOPT_UNLOCKFUNC. + +Note that some items are specifically documented as not thread-safe in the +share API (the connection pool and HSTS cache for example). .SH TLS If you are accessing HTTPS or FTPS URLs in a multi-threaded manner, you are then of course using the underlying SSL library multi-threaded and those libs @@ -69,8 +73,7 @@ The engine is used by libcurl in a way that is fully thread-safe. The engine is used by libcurl in a way that is fully thread-safe. .IP AWS-LC The engine is used by libcurl in a way that is fully thread-safe. -.SH "Other areas of caution" -.IP Signals +.SH "Signals" Signals are used for timing out name resolves (during DNS lookup) - when built without using either the c-ares or threaded resolver backends. When using multiple threads you should set the \fICURLOPT_NOSIGNAL(3)\fP option to 1L for @@ -86,16 +89,17 @@ with the risk of a SIGPIPE (that at least the OpenSSL backend can trigger). Note that setting \fICURLOPT_NOSIGNAL(3)\fP to 0L will not work in a threaded situation as there will be race where libcurl risks restoring the former signal handler while another thread should still ignore it. -.IP "Name resolving" -\fBgethostby* functions and other system calls.\fP These functions, provided -by your operating system, must be thread safe. It is important that libcurl -can find and use thread safe versions of these and other system calls, as -otherwise it cannot function fully thread safe. Some operating systems are -known to have faulty thread implementations. We have previously received -problem reports on *BSD (at least in the past, they may be working fine these -days). Some operating systems that are known to have solid and working thread -support are Linux, Solaris and Windows. -.IP "curl_global_* functions" +.SH "Name resolving" +The \fBgethostbyname\fP or \fBgetaddrinfo\fP and other name resolving system +calls used by libcurl are provided by your operating system and must be thread +safe. It is important that libcurl can find and use thread safe versions of +these and other system calls, as otherwise it cannot function fully thread +safe. Some operating systems are known to have faulty thread +implementations. We have previously received problem reports on *BSD (at least +in the past, they may be working fine these days). Some operating systems that +are known to have solid and working thread support are Linux, Solaris and +Windows. +.SH "curl_global_* functions" These functions are thread-safe since libcurl 7.84.0 if \fIcurl_version_info(3)\fP has the \fBCURL_VERSION_THREADSAFE\fP feature bit set (most platforms). @@ -107,11 +111,11 @@ initialize the library and its dependents, rather than rely on the "lazy" fail-safe initialization that takes place the first time \fIcurl_easy_init(3)\fP is called. For an in-depth explanation refer to \fIlibcurl(3)\fP section \fBGLOBAL CONSTANTS\fP. -.IP "Memory functions" +.SH "Memory functions" These functions, provided either by your operating system or your own replacements, must be thread safe. You can use \fIcurl_global_init_mem(3)\fP to set your own replacement memory functions. -.IP "Non-safe functions" +.SH "Non-safe functions" \fICURLOPT_DNS_USE_GLOBAL_CACHE(3)\fP is not thread-safe. \fIcurl_version_info(3)\fP is not thread-safe before libcurl initialization.