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Rework libpq threaded SIGPIPE handling to avoid interference with
calling applications. This is done by blocking sigpipe in the libpq thread and using sigpending/sigwait to possibily discard any sigpipe we generated.
This commit is contained in:
Bruce Momjian
@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/interfaces/libpq/fe-connect.c,v 1.290 2004/12/01 23:42:26 momjian Exp $
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* $PostgreSQL: pgsql/src/interfaces/libpq/fe-connect.c,v 1.291 2004/12/02 15:32:54 momjian Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -866,15 +866,6 @@ connectDBStart(PGconn *conn)
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const char *node = NULL;
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int ret;
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#ifdef ENABLE_THREAD_SAFETY
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#ifndef WIN32
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static pthread_once_t check_sigpipe_once = PTHREAD_ONCE_INIT;
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/* Check only on first connection request */
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pthread_once(&check_sigpipe_once, pq_check_sigpipe_handler);
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#endif
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#endif
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if (!conn)
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return 0;
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@ -10,7 +10,7 @@
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* didn't really belong there.
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/interfaces/libpq/fe-print.c,v 1.55 2004/11/09 15:57:57 petere Exp $
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* $PostgreSQL: pgsql/src/interfaces/libpq/fe-print.c,v 1.56 2004/12/02 15:32:54 momjian Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -91,7 +91,11 @@ PQprint(FILE *fout,
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int total_line_length = 0;
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int usePipe = 0;
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char *pagerenv;
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#ifdef ENABLE_THREAD_SAFETY
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sigset_t osigset;
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bool sigpipe_masked = false;
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bool sigpipe_pending;
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#endif
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#if !defined(ENABLE_THREAD_SAFETY) && !defined(WIN32)
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pqsigfunc oldsigpipehandler = NULL;
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#endif
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@ -189,7 +193,8 @@ PQprint(FILE *fout,
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{
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usePipe = 1;
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#ifdef ENABLE_THREAD_SAFETY
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pthread_setspecific(pq_thread_in_send, "t");
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pq_block_sigpipe(&osigset, &sigpipe_pending);
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sigpipe_masked = true;
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#else
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#ifndef WIN32
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oldsigpipehandler = pqsignal(SIGPIPE, SIG_IGN);
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@ -311,7 +316,8 @@ PQprint(FILE *fout,
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pclose(fout);
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#endif
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#ifdef ENABLE_THREAD_SAFETY
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pthread_setspecific(pq_thread_in_send, "f");
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if (sigpipe_masked)
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pq_reset_sigpipe(&osigset, sigpipe_pending);
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#else
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#ifndef WIN32
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pqsignal(SIGPIPE, oldsigpipehandler);
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@ -11,7 +11,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/interfaces/libpq/fe-secure.c,v 1.57 2004/11/20 00:35:13 tgl Exp $
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* $PostgreSQL: pgsql/src/interfaces/libpq/fe-secure.c,v 1.58 2004/12/02 15:32:54 momjian Exp $
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*
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* NOTES
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* [ Most of these notes are wrong/obsolete, but perhaps not all ]
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@ -152,12 +152,6 @@ bool pq_initssllib = true;
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static SSL_CTX *SSL_context = NULL;
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#endif
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#ifdef ENABLE_THREAD_SAFETY
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static void sigpipe_handler_ignore_send(int signo);
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pthread_key_t pq_thread_in_send = 0; /* initializer needed on Darwin */
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static pqsigfunc pq_pipe_handler;
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#endif
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/* ------------------------------------------------------------ */
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/* Hardcoded values */
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/* ------------------------------------------------------------ */
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@ -379,9 +373,12 @@ ssize_t
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pqsecure_write(PGconn *conn, const void *ptr, size_t len)
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{
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ssize_t n;
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#ifdef ENABLE_THREAD_SAFETY
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pthread_setspecific(pq_thread_in_send, "t");
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sigset_t osigmask;
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bool sigpipe_pending;
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pq_block_sigpipe(&osigmask, &sigpipe_pending);
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#else
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#ifndef WIN32
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pqsigfunc oldsighandler = pqsignal(SIGPIPE, SIG_IGN);
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@ -452,9 +449,14 @@ pqsecure_write(PGconn *conn, const void *ptr, size_t len)
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else
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#endif
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n = send(conn->sock, ptr, len, 0);
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/*
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* Possible optimization: if sigpending() turns out to be an
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* expensive operation, we can set sigpipe_pending = 'true'
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* here if errno != EPIPE, avoiding a sigpending call.
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*/
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#ifdef ENABLE_THREAD_SAFETY
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pthread_setspecific(pq_thread_in_send, "f");
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pq_reset_sigpipe(&osigmask, sigpipe_pending);
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#else
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#ifndef WIN32
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pqsignal(SIGPIPE, oldsighandler);
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@ -1216,65 +1218,77 @@ PQgetssl(PGconn *conn)
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}
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#endif /* USE_SSL */
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#ifdef ENABLE_THREAD_SAFETY
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#ifndef WIN32
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/*
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* Check SIGPIPE handler and perhaps install our own.
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* Block SIGPIPE for this thread. This prevents send()/write() from exiting
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* the application.
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*/
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void
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pq_check_sigpipe_handler(void)
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int
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pq_block_sigpipe(sigset_t *osigset, bool *sigpipe_pending)
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{
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pthread_key_create(&pq_thread_in_send, NULL);
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sigset_t sigpipe_sigset;
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sigset_t sigset;
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int ret;
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sigemptyset(&sigpipe_sigset);
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sigaddset(&sigpipe_sigset, SIGPIPE);
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/*
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* Find current pipe handler and chain on to it.
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*/
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pq_pipe_handler = pqsignalinquire(SIGPIPE);
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pqsignal(SIGPIPE, sigpipe_handler_ignore_send);
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}
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/* Block SIGPIPE and save previous mask for later reset */
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ret = pthread_sigmask(SIG_BLOCK, &sigpipe_sigset, osigset);
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/*
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* Threaded SIGPIPE signal handler
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*/
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void
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sigpipe_handler_ignore_send(int signo)
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{
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/*
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* If we have gotten a SIGPIPE outside send(), chain or exit if we are
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* at the end of the chain. Synchronous signals are delivered to the
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* thread that caused the signal.
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*/
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if (!PQinSend())
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/* We can have a pending SIGPIPE only if it was blocked before */
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if (sigismember(osigset, SIGPIPE))
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{
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if (pq_pipe_handler == SIG_DFL) /* not set by application */
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exit(128 + SIGPIPE); /* typical return value for SIG_DFL */
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/* Is there a pending SIGPIPE? */
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if (sigpending(&sigset) != 0)
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return -1;
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if (sigismember(&sigset, SIGPIPE))
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*sigpipe_pending = true;
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else
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(*pq_pipe_handler) (signo); /* call original handler */
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*sigpipe_pending = false;
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}
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else
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*sigpipe_pending = false;
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return ret;
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}
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#endif
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#endif
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/*
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* Indicates whether the current thread is in send()
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* For use by SIGPIPE signal handlers; they should
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* ignore SIGPIPE when libpq is in send(). This means
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* that the backend has died unexpectedly.
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* Discard any pending SIGPIPE and reset the signal mask.
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* We might be discarding a blocked SIGPIPE that we didn't generate,
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* but we document that you can't keep blocked SIGPIPE calls across
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* libpq function calls.
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*/
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pqbool
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PQinSend(void)
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int
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pq_reset_sigpipe(sigset_t *osigset, bool sigpipe_pending)
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{
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#ifdef ENABLE_THREAD_SAFETY
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return (pthread_getspecific(pq_thread_in_send) /* has it been set? */ &&
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*(char *) pthread_getspecific(pq_thread_in_send) == 't') ? true : false;
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#else
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int signo;
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sigset_t sigset;
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/*
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* No threading: our code ignores SIGPIPE around send(). Therefore, we
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* can't be in send() if we are checking from a SIGPIPE signal
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* handler.
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*/
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return false;
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#endif
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/* Clear SIGPIPE only if none was pending */
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if (!sigpipe_pending)
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{
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if (sigpending(&sigset) != 0)
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return -1;
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/*
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* Discard pending and blocked SIGPIPE
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*/
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if (sigismember(&sigset, SIGPIPE))
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{
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sigset_t sigpipe_sigset;
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sigemptyset(&sigpipe_sigset);
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sigaddset(&sigpipe_sigset, SIGPIPE);
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sigwait(&sigpipe_sigset, &signo);
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if (signo != SIGPIPE)
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return -1;
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}
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}
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/* Restore saved block mask */
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return pthread_sigmask(SIG_SETMASK, osigset, NULL);
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}
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#endif
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@ -7,7 +7,7 @@
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* Portions Copyright (c) 1996-2004, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/interfaces/libpq/libpq-fe.h,v 1.113 2004/10/30 23:11:27 tgl Exp $
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* $PostgreSQL: pgsql/src/interfaces/libpq/libpq-fe.h,v 1.114 2004/12/02 15:32:54 momjian Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -497,12 +497,6 @@ extern int PQenv2encoding(void);
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/* === in fe-secure.c === */
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/*
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* Indicates whether the libpq thread is in send().
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* Used to ignore SIGPIPE if thread is in send().
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*/
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extern pqbool PQinSend(void);
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#ifdef __cplusplus
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}
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#endif
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@ -12,7 +12,7 @@
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* Portions Copyright (c) 1996-2004, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* $PostgreSQL: pgsql/src/interfaces/libpq/libpq-int.h,v 1.96 2004/10/30 23:11:27 tgl Exp $
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* $PostgreSQL: pgsql/src/interfaces/libpq/libpq-int.h,v 1.97 2004/12/02 15:32:54 momjian Exp $
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*
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*-------------------------------------------------------------------------
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*/
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@ -31,6 +31,7 @@
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#ifdef ENABLE_THREAD_SAFETY
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#include <pthread.h>
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#include <signal.h>
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#endif
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#ifdef WIN32_CLIENT_ONLY
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@ -475,15 +476,15 @@ extern void pqsecure_close(PGconn *);
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extern ssize_t pqsecure_read(PGconn *, void *ptr, size_t len);
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extern ssize_t pqsecure_write(PGconn *, const void *ptr, size_t len);
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#ifdef ENABLE_THREAD_SAFETY
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extern void pq_check_sigpipe_handler(void);
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extern pthread_key_t pq_thread_in_send;
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#endif
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#ifdef USE_SSL
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extern bool pq_initssllib;
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#endif
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#ifdef ENABLE_THREAD_SAFETY
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int pq_block_sigpipe(sigset_t *osigset, bool *sigpipe_pending);
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int pq_reset_sigpipe(sigset_t *osigset, bool sigpipe_pending);
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#endif
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/*
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* this is so that we can check if a connection is non-blocking internally
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* without the overhead of a function call
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