From 5b860ec3ecdc7e07f7a6dc1b88c283ec05ef69e2 Mon Sep 17 00:00:00 2001
From: Andrew Johnson <anj@aps.anl.gov>
Date: Thu, 23 Sep 2010 15:09:03 -0500
Subject: [PATCH] libCom: Use SIG_IGN to ignore signals.

Simplified the code in osdSignal, also solves problems if a handler is
already installed that uses the 3-argument callback.
---
 src/libCom/osi/os/posix/osdSignal.cpp | 105 +++++---------------------
 1 file changed, 17 insertions(+), 88 deletions(-)

diff --git a/src/libCom/osi/os/posix/osdSignal.cpp b/src/libCom/osi/os/posix/osdSignal.cpp
index 420176427..3f8deb4fb 100644
--- a/src/libCom/osi/os/posix/osdSignal.cpp
+++ b/src/libCom/osi/os/posix/osdSignal.cpp
@@ -1,5 +1,5 @@
 /*************************************************************************\
- * Copyright (c) 2002 The University of Chicago, as Operator of Argonne
+ * Copyright (c) 2010 UChicago Argonne LLC, as Operator of Argonne
  *     National Laboratory.
  * Copyright (c) 2002 The Regents of the University of California, as
  *     Operator of Los Alamos National Laboratory.
@@ -8,7 +8,7 @@
 \*************************************************************************/
 
 /*
- * Author: J. Hill
+ * Authors: J. Hill, A. Johnson
  */
 
 #include <signal.h>
@@ -17,81 +17,22 @@
 #include <string.h>
 
 #define epicsExportSharedSymbols
-#include "epicsThread.h"
 #include "epicsSignal.h"
-#include "errlog.h"
 
-extern "C" {
-typedef void ( *pSigFunc ) ( int );
-}
-
-static pSigFunc pReplacedSigHupFunc = 0;
-static pSigFunc pReplacedSigPipeFunc = 0;
-
-/*
- * localInstallSigHandler ()
- */
-static void localInstallSigHandler ( int signalIn, pSigFunc pNewFunc,
-                                   pSigFunc * pReplacedFunc )
+static void ignoreIfDefault(int signum, const char *name)
 {
-    // install the handler
-    struct sigaction newAction;
-    struct sigaction oldAction;
-    newAction.sa_handler = pNewFunc;
-    int status = sigemptyset ( & newAction.sa_mask );
-    assert ( ! status );
-    newAction.sa_flags = 0;
-    status = sigaction ( signalIn, & newAction, & oldAction );
-    if ( status < 0 ) {
-        fprintf ( stderr, "%s: ignore install for signal %d failed beacuse %s\n", 
-            __FILE__, signalIn, strerror ( errno ) );
+    struct sigaction curAction;
+    int status = sigaction(signum, NULL, &curAction);
+
+    if (status >= 0 &&
+        curAction.sa_handler == SIG_DFL) {
+        curAction.sa_handler = SIG_IGN;
+        status = sigaction(signum, &curAction, NULL);
     }
-    else if (   oldAction.sa_handler != SIG_DFL && 
-                oldAction.sa_handler != SIG_IGN &&
-                oldAction.sa_handler != pNewFunc ) {
-        *pReplacedFunc = oldAction.sa_handler;
+    if (status < 0) {
+        fprintf(stderr, "%s: sigaction failed for %s, %s\n",
+            __FILE__, name, strerror(errno));
     }
-
-    // enable delivery
-    sigset_t mask;
-    status = sigemptyset ( & mask );
-    assert ( ! status );
-    status = sigaddset ( & mask, signalIn );
-    assert ( ! status );
-    status = pthread_sigmask ( SIG_UNBLOCK, & mask, 0 );
-    assert ( ! status );
-}
-
-/*
- * ignoreSigHup ()
- */
-extern "C" {
-static void ignoreSigHup ( int signal )
-{
-    static volatile int reentered = 1;
-
-    if (--reentered == 0) {
-        if ( pReplacedSigHupFunc ) {
-            ( *pReplacedSigHupFunc ) ( signal );
-        }
-    }
-}
-}
-
-/*
- * ignoreSigPipe ()
- */
-extern "C" {
-static void ignoreSigPipe ( int signal )
-{
-    static volatile int reentered = 1;
-
-    if (--reentered == 0) {
-        if ( pReplacedSigPipeFunc ) {
-            ( *pReplacedSigPipeFunc ) ( signal );
-        }
-    }
-}
 }
 
 /*
@@ -99,8 +40,7 @@ static void ignoreSigPipe ( int signal )
  */
 epicsShareFunc void epicsShareAPI epicsSignalInstallSigHupIgnore (void)
 {
-    localInstallSigHandler ( SIGHUP, 
-        ignoreSigHup, & pReplacedSigHupFunc );
+    ignoreIfDefault(SIGHUP, "SIGHUP");
 }
 
 /*
@@ -108,21 +48,10 @@ epicsShareFunc void epicsShareAPI epicsSignalInstallSigHupIgnore (void)
  */
 epicsShareFunc void epicsShareAPI epicsSignalInstallSigPipeIgnore (void)
 {
-    localInstallSigHandler ( SIGPIPE, 
-        ignoreSigPipe, & pReplacedSigPipeFunc );
+    ignoreIfDefault(SIGPIPE, "SIGPIPE");
 }
 
-/*
- * epicsSignalInstallSigAlarmIgnore ()
- */
-epicsShareFunc void epicsShareAPI epicsSignalInstallSigAlarmIgnore ( void )
-{
-    // Removed; this functionality was only required by HPUX,
-    // and it interferes with the posix timer API on Linux.
-}
-
-/*
- * epicsSignalRaiseSigAlarm ()
- */
+/* Disabled */
+epicsShareFunc void epicsShareAPI epicsSignalInstallSigAlarmIgnore ( void ) {}
 epicsShareFunc void epicsShareAPI epicsSignalRaiseSigAlarm 
                                   ( struct epicsThreadOSD * /* threadId */ ) {}