From 008e7b3121f544cc296ae8c27eda39e9b598745c Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Wed, 17 Feb 2010 20:43:34 +0000
Subject: [PATCH] under linux, run write-barrier signal handler on alternate
 stack

svn: r18124
---
 src/mzscheme/gc2/sighand.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/src/mzscheme/gc2/sighand.c b/src/mzscheme/gc2/sighand.c
index 6512d3b61e..426aa593e8 100644
--- a/src/mzscheme/gc2/sighand.c
+++ b/src/mzscheme/gc2/sighand.c
@@ -41,8 +41,6 @@ static void launchgdb() {
 void fault_handler(int sn, struct siginfo *si, void *ctx)
 {
   void *p = si->si_addr;
-  int c = si->si_code;
-  int m = 0;
   if (si->si_code != SEGV_ACCERR) { /*SEGV_MAPERR*/
     printf("SIGSEGV fault on %p\n", p);
 #if WAIT_FOR_GDB
@@ -66,6 +64,7 @@ void fault_handler(int sn, struct siginfo *si, void *ctx)
     }
     abort();
   }
+#  define NEED_SIGSTACK
 #  define NEED_SIGACTION
 #  define USE_SIGACTON_SIGNAL_KIND SIGSEGV
 }
@@ -153,6 +152,17 @@ static void initialize_signal_handler(GCTYPE *gc)
   macosx_init_exception_handler(1);
 #  endif
 # endif
+# ifdef NEED_SIGSTACK
+  {
+    stack_t ss;
+    
+    ss.ss_sp = malloc(SIGSTKSZ);
+    ss.ss_size = SIGSTKSZ;
+    ss.ss_flags = 0;
+    
+    sigaltstack(&ss, NULL);
+  }
+# endif
 # ifdef NEED_SIGACTION
   {
     struct sigaction act, oact;
@@ -163,6 +173,9 @@ static void initialize_signal_handler(GCTYPE *gc)
     sigaddset(&act.sa_mask, SIGINT);
     sigaddset(&act.sa_mask, SIGCHLD);
     act.sa_flags = SA_SIGINFO;
+#  ifdef NEED_SIGSTACK
+    act.sa_flags |= SA_ONSTACK;
+#  endif
     sigaction(USE_SIGACTON_SIGNAL_KIND, &act, &oact);
   }
 # endif