Fixed "changing binary" when reaper is not init.

On some systems, it's possible that reaper of orphaned processes is
set to something other than "init" process.  On such systems, the
changing binary procedure did not work.

The fix is to check if PPID has changed, instead of assuming it's
always 1 for orphaned processes.

src/core/nginx.c

diff --git a/src/core/nginx.c b/src/core/nginx.c
index c3a29cc..3894c29 100644
--- a/src/core/nginx.c
+++ b/src/core/nginx.c
@@ -228,6 +228,7 @@
 #endif
 
     ngx_pid = ngx_getpid();
+    ngx_parent = ngx_getppid();
 
     log = ngx_log_init(ngx_prefix);
     if (log == NULL) {

src/os/unix/ngx_daemon.c

diff --git a/src/os/unix/ngx_daemon.c b/src/os/unix/ngx_daemon.c
index ab67211..385c49b 100644
--- a/src/os/unix/ngx_daemon.c
+++ b/src/os/unix/ngx_daemon.c
@@ -26,6 +26,7 @@
         exit(0);
     }
 
+    ngx_parent = ngx_pid;
     ngx_pid = ngx_getpid();
 
     if (setsid() == -1) {

src/os/unix/ngx_process.c

diff --git a/src/os/unix/ngx_process.c b/src/os/unix/ngx_process.c
index 993c032..1568023 100644
--- a/src/os/unix/ngx_process.c
+++ b/src/os/unix/ngx_process.c
@@ -194,6 +194,7 @@
         return NGX_INVALID_PID;
 
     case 0:
+        ngx_parent = ngx_pid;
         ngx_pid = ngx_getpid();
         proc(cycle, data);
         break;
@@ -371,12 +372,12 @@
             break;
 
         case ngx_signal_value(NGX_CHANGEBIN_SIGNAL):
-            if (getppid() > 1 || ngx_new_binary > 0) {
+            if (ngx_getppid() == ngx_parent || ngx_new_binary > 0) {
 
                 /*
                  * Ignore the signal in the new binary if its parent is
-                 * not the init process, i.e. the old binary's process
-                 * is still running.  Or ignore the signal in the old binary's
+                 * not changed, i.e. the old binary's process is still
+                 * running.  Or ignore the signal in the old binary's
                  * process if the new binary's process is already running.
                  */
 

src/os/unix/ngx_process.h

diff --git a/src/os/unix/ngx_process.h b/src/os/unix/ngx_process.h
index 7b5e8c0..3986639 100644
--- a/src/os/unix/ngx_process.h
+++ b/src/os/unix/ngx_process.h
@@ -54,6 +54,7 @@
 
 
 #define ngx_getpid   getpid
+#define ngx_getppid  getppid
 
 #ifndef ngx_log_pid
 #define ngx_log_pid  ngx_pid
@@ -79,6 +80,7 @@
 extern char         **ngx_os_argv;
 
 extern ngx_pid_t      ngx_pid;
+extern ngx_pid_t      ngx_parent;
 extern ngx_socket_t   ngx_channel;
 extern ngx_int_t      ngx_process_slot;
 extern ngx_int_t      ngx_last_process;

src/os/unix/ngx_process_cycle.c

diff --git a/src/os/unix/ngx_process_cycle.c b/src/os/unix/ngx_process_cycle.c
index 1710ea8..a20a515 100644
--- a/src/os/unix/ngx_process_cycle.c
+++ b/src/os/unix/ngx_process_cycle.c
@@ -31,6 +31,7 @@
 ngx_uint_t    ngx_process;
 ngx_uint_t    ngx_worker;
 ngx_pid_t     ngx_pid;
+ngx_pid_t     ngx_parent;
 
 sig_atomic_t  ngx_reap;
 sig_atomic_t  ngx_sigio;

src/os/win32/ngx_process.h

diff --git a/src/os/win32/ngx_process.h b/src/os/win32/ngx_process.h
index a6a5aa2..7ec4cd9 100644
--- a/src/os/win32/ngx_process.h
+++ b/src/os/win32/ngx_process.h
@@ -14,6 +14,7 @@
 
 
 #define ngx_getpid          GetCurrentProcessId
+#define ngx_getppid()       0
 #define ngx_log_pid         ngx_pid
 
 
@@ -73,6 +74,7 @@
 extern ngx_process_t        ngx_processes[NGX_MAX_PROCESSES];
 
 extern ngx_pid_t            ngx_pid;
+extern ngx_pid_t            ngx_parent;
 
 
 #endif /* _NGX_PROCESS_H_INCLUDED_ */

src/os/win32/ngx_process_cycle.c

diff --git a/src/os/win32/ngx_process_cycle.c b/src/os/win32/ngx_process_cycle.c
index 293b967..3aea874 100644
--- a/src/os/win32/ngx_process_cycle.c
+++ b/src/os/win32/ngx_process_cycle.c
@@ -31,6 +31,7 @@
 ngx_uint_t     ngx_process;
 ngx_uint_t     ngx_worker;
 ngx_pid_t      ngx_pid;
+ngx_pid_t      ngx_parent;
 
 ngx_uint_t     ngx_inherited;
 ngx_pid_t      ngx_new_binary;