Re: SIGPIPE handling

Better. However, I am confused over when we do sigaction. I thought we
were going to do it only if they had a signal handler defined, meaning

if (pipehandler != SIG_DFL &&
pipehandler != SIG_IGN &&
pipehandler != SIG_ERR)
conn->do_sigaction = true;
else
conn->do_sigaction = false;

By doing this, we don't do sigaction in the default case where no
handler was defined. I thought we would just set the entire application
to SIGPIPE <= SIG_IGN. This gives us good performance in all cases
except when a signal handler is defined. Is running the rest of the
application with SIGPIPE <= SIG_IGN a problem?

However, the code patch is:

if (pipehandler == SIG_DFL || pipehandler == SIG_ERR)
conn->do_sigaction = true;
else
conn->do_sigaction = false;

This gives us good performance only if SIGPIPE <= SIG_IGN has been set
by the application or a sigaction function has been defined.

---------------------------------------------------------------------------

Manfred Spraul wrote:
> Hi,
>
> attached is an update of my automatic sigaction patch: I've moved the
> actual sigaction calls into pqsignal.c and added a helper function
> (pgsignalinquire(signo)). I couldn't remove the include <signal.h> from
> fe-connect.c: it's required for the SIGPIPE definition.
> Additionally I've added a -a flag for pgbench that sets the signal
> handler before calling PQconnectdb.
>
> Tested on Fedora Core 1 (Redhat Linux) with pgbench.
>
> --
> Manfred

> Index: src/interfaces/libpq/fe-connect.c
> ===================================================================
> RCS file: /projects/cvsroot/pgsql-server/src/interfaces/libpq/fe-connect.c,v
> retrieving revision 1.263
> diff -c -r1.263 fe-connect.c
> *** src/interfaces/libpq/fe-connect.c 18 Oct 2003 05:02:06 -0000 1.263
> --- src/interfaces/libpq/fe-connect.c 16 Nov 2003 11:44:47 -0000
> ***************
> *** 41,46 ****
> --- 41,48 ----
> #include <netinet/tcp.h>
> #endif
> #include <arpa/inet.h>
> + #include <signal.h>
> + #include "pqsignal.h"
> #endif
>
> #include "libpq/ip.h"
> ***************
> *** 881,886 ****
> --- 883,891 ----
> struct addrinfo hint;
> const char *node = NULL;
> int ret;
> + #ifndef WIN32
> + pqsigfunc pipehandler;
> + #endif
>
> if (!conn)
> return 0;
> ***************
> *** 950,955 ****
> --- 955,976 ----
> conn->allow_ssl_try = false;
> else if (conn->sslmode[0] == 'a') /* "allow" */
> conn->wait_ssl_try = true;
> + #endif
> + #ifndef WIN32
> + /*
> + * Autodetect SIGPIPE signal handling:
> + * The default action per Unix spec is kill current process and
> + * that's not acceptable. If the current setting is not the default,
> + * then assume that the caller knows what he's doing and leave the
> + * signal handler unchanged. Otherwise set the signal handler to
> + * SIG_IGN around each send() syscall. Unfortunately this is both
> + * unreliable and slow for multithreaded apps.
> + */
> + pipehandler = pqsignalinquire(SIGPIPE);
> + if (pipehandler == SIG_DFL || pipehandler == SIG_ERR)
> + conn->do_sigaction = true;
> + else
> + conn->do_sigaction = false;
> #endif
>
> /*
> Index: src/interfaces/libpq/fe-secure.c
> ===================================================================
> RCS file: /projects/cvsroot/pgsql-server/src/interfaces/libpq/fe-secure.c,v
> retrieving revision 1.32
> diff -c -r1.32 fe-secure.c
> *** src/interfaces/libpq/fe-secure.c 29 Sep 2003 16:38:04 -0000 1.32
> --- src/interfaces/libpq/fe-secure.c 16 Nov 2003 11:44:47 -0000
> ***************
> *** 348,354 ****
> ssize_t n;
>
> #ifndef WIN32
> ! pqsigfunc oldsighandler = pqsignal(SIGPIPE, SIG_IGN);
> #endif
>
> #ifdef USE_SSL
> --- 348,357 ----
> ssize_t n;
>
> #ifndef WIN32
> ! pqsigfunc oldsighandler = NULL;
> !
> ! if (conn->do_sigaction)
> ! oldsighandler = pqsignal(SIGPIPE, SIG_IGN);
> #endif
>
> #ifdef USE_SSL
> ***************
> *** 408,414 ****
> n = send(conn->sock, ptr, len, 0);
>
> #ifndef WIN32
> ! pqsignal(SIGPIPE, oldsighandler);
> #endif
>
> return n;
> --- 411,418 ----
> n = send(conn->sock, ptr, len, 0);
>
> #ifndef WIN32
> ! if (conn->do_sigaction)
> ! pqsignal(SIGPIPE, oldsighandler);
> #endif
>
> return n;
> Index: src/interfaces/libpq/libpq-int.h
> ===================================================================
> RCS file: /projects/cvsroot/pgsql-server/src/interfaces/libpq/libpq-int.h,v
> retrieving revision 1.82
> diff -c -r1.82 libpq-int.h
> *** src/interfaces/libpq/libpq-int.h 5 Sep 2003 02:08:36 -0000 1.82
> --- src/interfaces/libpq/libpq-int.h 16 Nov 2003 11:44:48 -0000
> ***************
> *** 329,334 ****
> --- 329,337 ----
> char peer_dn[256 + 1]; /* peer distinguished name */
> char peer_cn[SM_USER + 1]; /* peer common name */
> #endif
> + #ifndef WIN32
> + bool do_sigaction; /* set SIGPIPE to SIG_IGN around every send() call */
> + #endif
>
> /* Buffer for current error message */
> PQExpBufferData errorMessage; /* expansible string */
> Index: src/interfaces/libpq/pqsignal.c
> ===================================================================
> RCS file: /projects/cvsroot/pgsql-server/src/interfaces/libpq/pqsignal.c,v
> retrieving revision 1.17
> diff -c -r1.17 pqsignal.c
> *** src/interfaces/libpq/pqsignal.c 4 Aug 2003 02:40:20 -0000 1.17
> --- src/interfaces/libpq/pqsignal.c 16 Nov 2003 11:44:48 -0000
> ***************
> *** 40,42 ****
> --- 40,61 ----
> return oact.sa_handler;
> #endif /* !HAVE_POSIX_SIGNALS */
> }
> +
> + pqsigfunc
> + pqsignalinquire(int signo)
> + {
> + #if !defined(HAVE_POSIX_SIGNALS)
> + pqsigfunc old;
> + old = signal(SIGPIPE, SIG_IGN);
> + signal(SIGPIPE, old);
> + return old;
> + #else
> + struct sigaction oact;
> +
> + if (sigaction(SIGPIPE, NULL, &oact) != 0)
> + return SIG_ERR;
> + return oact.sa_handler;
> + #endif /* !HAVE_POSIX_SIGNALS */
> +
> +
> + }
> Index: src/interfaces/libpq/pqsignal.h
> ===================================================================
> RCS file: /projects/cvsroot/pgsql-server/src/interfaces/libpq/pqsignal.h,v
> retrieving revision 1.15
> diff -c -r1.15 pqsignal.h
> *** src/interfaces/libpq/pqsignal.h 4 Aug 2003 02:40:20 -0000 1.15
> --- src/interfaces/libpq/pqsignal.h 16 Nov 2003 11:44:48 -0000
> ***************
> *** 24,27 ****
> --- 24,29 ----
>
> extern pqsigfunc pqsignal(int signo, pqsigfunc func);
>
> + extern pqsigfunc pqsignalinquire(int signo);
> +
> #endif /* PQSIGNAL_H */

> Index: contrib/pgbench/README.pgbench
> ===================================================================
> RCS file: /projects/cvsroot/pgsql-server/contrib/pgbench/README.pgbench,v
> retrieving revision 1.9
> diff -c -r1.9 README.pgbench
> *** contrib/pgbench/README.pgbench 10 Jun 2003 09:07:15 -0000 1.9
> --- contrib/pgbench/README.pgbench 16 Nov 2003 11:44:39 -0000
> ***************
> *** 112,117 ****
> --- 112,121 ----
> might be a security hole since ps command will
> show the password. Use this for TESTING PURPOSE ONLY.
>
> + -a
> + Disable SIGPIPE delivery globally instead of within each
> + libpq operation.
> +
> -n
> No vacuuming and cleaning the history table prior to the
> test is performed.
> Index: contrib/pgbench/pgbench.c
> ===================================================================
> RCS file: /projects/cvsroot/pgsql-server/contrib/pgbench/pgbench.c,v
> retrieving revision 1.27
> diff -c -r1.27 pgbench.c
> *** contrib/pgbench/pgbench.c 27 Sep 2003 19:15:34 -0000 1.27
> --- contrib/pgbench/pgbench.c 16 Nov 2003 11:44:39 -0000
> ***************
> *** 28,33 ****
> --- 28,34 ----
> #else
> #include <sys/time.h>
> #include <unistd.h>
> + #include <signal.h>
>
> #ifdef HAVE_GETOPT_H
> #include <getopt.h>
> ***************
> *** 105,112 ****
> static void
> usage()
> {
> ! fprintf(stderr, "usage: pgbench [-h hostname][-p port][-c nclients][-t ntransactions][-s scaling_factor][-n][-C][-v][-S][-N][-l][-U login][-P password][-d][dbname]\n");
> ! fprintf(stderr, "(initialize mode): pgbench -i [-h hostname][-p port][-s scaling_factor][-U login][-P password][-d][dbname]\n");
> }
>
> /* random number generator */
> --- 106,113 ----
> static void
> usage()
> {
> ! fprintf(stderr, "usage: pgbench [-h hostname][-p port][-c nclients][-t ntransactions][-s scaling_factor][-n][-C][-v][-S][-N][-l][-a][-U login][-P password][-d][dbname]\n");
> ! fprintf(stderr, "(initialize mode): pgbench -i [-h hostname][-p port][-s scaling_factor][-U login][-P password][-d][dbname][-a]\n");
> }
>
> /* random number generator */
> ***************
> *** 703,712 ****
> else if ((env = getenv("PGUSER")) != NULL && *env != '\0')
> login = env;
>
> ! while ((c = getopt(argc, argv, "ih:nvp:dc:t:s:U:P:CNSl")) != -1)
> {
> switch (c)
> {
> case 'i':
> is_init_mode++;
> break;
> --- 704,718 ----
> else if ((env = getenv("PGUSER")) != NULL && *env != '\0')
> login = env;
>
> ! while ((c = getopt(argc, argv, "aih:nvp:dc:t:s:U:P:CNSl")) != -1)
> {
> switch (c)
> {
> + case 'a':
> + #ifndef WIN32
> + signal(SIGPIPE, SIG_IGN);
> + #endif
> + break;
> case 'i':
> is_init_mode++;
> break;

>
> ---------------------------(end of broadcast)---------------------------
> TIP 4: Don't 'kill -9' the postmaster

--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
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+ Christ can be your backup. | Newtown Square, Pennsylvania 19073