Don't use an alternative stack for SIGSEGV & co.

This commit reverts most of c575766202773c858be0870c20cd495b722927c3, in
order to use back main stack for signal handling.

The main reason is that otherwise it is completely pointless that we do
a lot of efforts to print the stack trace on crash, and the content of
the stack and registers as well. Using an alternate stack broken this
feature completely.

diff --git a/src/redis.c b/src/redis.c
index 08995115163b29f5e62f6f11bf7553ddc354a532..e2f9024b30a4df055540d95f3e24f7c3dd1fc4c5 100644 (file)
--- a/src/redis.c
+++ b/src/redis.c
@@ -62,9 +62,6 @@ double R_Zero, R_PosInf, R_NegInf, R_Nan;
 
 /*================================= Globals ================================= */
 
 
 /*================================= Globals ================================= */
 

-/* Alternate stack for SIGSEGV/etc handlers */
-char altstack[SIGSTKSZ];
-

 /* Global vars */
 struct redisServer server; /* server global state */
 struct redisCommand *commandTable;
 /* Global vars */
 struct redisServer server; /* server global state */
 struct redisCommand *commandTable;


@@ -2300,13 +2297,6 @@ static void sigtermHandler(int sig) {
 
 void setupSignalHandlers(void) {
     struct sigaction act;
 
 void setupSignalHandlers(void) {
     struct sigaction act;

-    stack_t stack;
-
-    stack.ss_sp = altstack;
-    stack.ss_flags = 0;
-    stack.ss_size = SIGSTKSZ;
-
-    sigaltstack(&stack, NULL);

 
     /* When the SA_SIGINFO flag is set in sa_flags then sa_sigaction is used.
      * Otherwise, sa_handler is used. */
 
     /* When the SA_SIGINFO flag is set in sa_flags then sa_sigaction is used.
      * Otherwise, sa_handler is used. */


@@ -2316,10 +2306,8 @@ void setupSignalHandlers(void) {
     sigaction(SIGTERM, &act, NULL);
 
 #ifdef HAVE_BACKTRACE
     sigaction(SIGTERM, &act, NULL);
 
 #ifdef HAVE_BACKTRACE

-    /* Use alternate stack so we don't clobber stack in case of segv, or when we run out of stack ..
-     * also resethand & nodefer so we can get interrupted (and killed) if we cause SEGV during SEGV handler */

     sigemptyset(&act.sa_mask);
     sigemptyset(&act.sa_mask);

-    act.sa_flags = SA_NODEFER | SA_ONSTACK | SA_RESETHAND | SA_SIGINFO;
+    act.sa_flags = SA_NODEFER | SA_RESETHAND | SA_SIGINFO;

     act.sa_sigaction = sigsegvHandler;
     sigaction(SIGSEGV, &act, NULL);
     sigaction(SIGBUS, &act, NULL);
     act.sa_sigaction = sigsegvHandler;
     sigaction(SIGSEGV, &act, NULL);
     sigaction(SIGBUS, &act, NULL);