147 lines
4.4 KiB
C
147 lines
4.4 KiB
C
/*-------------------------------------------------------------------------
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*
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* thread.c
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*
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* Prototypes and macros around system calls, used to help make
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* threaded libraries reentrant and safe to use from threaded applications.
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*
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* Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
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*
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* src/port/thread.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "c.h"
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#include <pwd.h>
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/*
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* Threading sometimes requires specially-named versions of functions
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* that return data in static buffers, like strerror_r() instead of
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* strerror(). Other operating systems use pthread_setspecific()
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* and pthread_getspecific() internally to allow standard library
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* functions to return static data to threaded applications. And some
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* operating systems have neither.
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*
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* Additional confusion exists because many operating systems that
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* use pthread_setspecific/pthread_getspecific() also have *_r versions
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* of standard library functions for compatibility with operating systems
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* that require them. However, internally, these *_r functions merely
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* call the thread-safe standard library functions.
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*
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* For example, BSD/OS 4.3 uses Bind 8.2.3 for getpwuid(). Internally,
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* getpwuid() calls pthread_setspecific/pthread_getspecific() to return
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* static data to the caller in a thread-safe manner. However, BSD/OS
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* also has getpwuid_r(), which merely calls getpwuid() and shifts
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* around the arguments to match the getpwuid_r() function declaration.
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* Therefore, while BSD/OS has getpwuid_r(), it isn't required. It also
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* doesn't have strerror_r(), so we can't fall back to only using *_r
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* functions for threaded programs.
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*
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* The current setup is to try threading in this order:
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*
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* use *_r function names if they exit
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* (*_THREADSAFE=yes)
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* use non-*_r functions if they are thread-safe
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*
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* One thread-safe solution for gethostbyname() might be to use getaddrinfo().
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*
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* Run src/test/thread to test if your operating system has thread-safe
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* non-*_r functions.
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*/
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/*
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* Wrapper around strerror and strerror_r to use the former if it is
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* available and also return a more useful value (the error string).
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*/
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char *
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pqStrerror(int errnum, char *strerrbuf, size_t buflen)
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{
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#if defined(FRONTEND) && defined(ENABLE_THREAD_SAFETY) && defined(HAVE_STRERROR_R)
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/* reentrant strerror_r is available */
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#ifdef STRERROR_R_INT
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/* SUSv3 version */
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if (strerror_r(errnum, strerrbuf, buflen) == 0)
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return strerrbuf;
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else
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return "Unknown error";
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#else
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/* GNU libc */
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return strerror_r(errnum, strerrbuf, buflen);
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#endif
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#else
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/* no strerror_r() available, just use strerror */
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strlcpy(strerrbuf, strerror(errnum), buflen);
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return strerrbuf;
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#endif
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}
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/*
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* Wrapper around getpwuid() or getpwuid_r() to mimic POSIX getpwuid_r()
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* behaviour, if that function is not available or required.
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*
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* Per POSIX, the possible cases are:
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* success: returns zero, *result is non-NULL
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* uid not found: returns zero, *result is NULL
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* error during lookup: returns an errno code, *result is NULL
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* (caller should *not* assume that the errno variable is set)
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*/
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#ifndef WIN32
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int
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pqGetpwuid(uid_t uid, struct passwd * resultbuf, char *buffer,
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size_t buflen, struct passwd ** result)
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{
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#if defined(FRONTEND) && defined(ENABLE_THREAD_SAFETY) && defined(HAVE_GETPWUID_R)
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return getpwuid_r(uid, resultbuf, buffer, buflen, result);
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#else
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/* no getpwuid_r() available, just use getpwuid() */
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errno = 0;
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*result = getpwuid(uid);
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/* paranoia: ensure we return zero on success */
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return (*result == NULL) ? errno : 0;
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#endif
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}
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#endif
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/*
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* Wrapper around gethostbyname() or gethostbyname_r() to mimic
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* POSIX gethostbyname_r() behaviour, if it is not available or required.
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* This function is called _only_ by our getaddinfo() portability function.
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*/
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#ifndef HAVE_GETADDRINFO
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int
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pqGethostbyname(const char *name,
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struct hostent * resultbuf,
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char *buffer, size_t buflen,
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struct hostent ** result,
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int *herrno)
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{
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#if defined(FRONTEND) && defined(ENABLE_THREAD_SAFETY) && defined(HAVE_GETHOSTBYNAME_R)
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/*
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* broken (well early POSIX draft) gethostbyname_r() which returns 'struct
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* hostent *'
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*/
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*result = gethostbyname_r(name, resultbuf, buffer, buflen, herrno);
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return (*result == NULL) ? -1 : 0;
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#else
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/* no gethostbyname_r(), just use gethostbyname() */
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*result = gethostbyname(name);
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if (*result != NULL)
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*herrno = h_errno;
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if (*result != NULL)
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return 0;
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else
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return -1;
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#endif
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}
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#endif
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