Changeset b4e3b2b in rtems

Timestamp:

10/28/98 19:25:12 (25 years ago)

Author:

Joel Sherrill <joel.sherrill@…>

Branches:

4.10, 4.11, 4.8, 4.9, 5, master

Children:

22fa5832

Parents:

692b9f7

Message:

Patch from Ian Lance Taylor <ian@…>.

I just happened across the sync_io support in

c/src/exec/score/cpu/unix/cpu.c

(is this documented anywhere?). That looked more useful than the
signal driven I/O I was using before, so I tried it. I ran across a
few bugs in the way it uses select.

Select changes its fd_set arguments, so you can't use global variables
for them. You have to copy them into local variables first.

If select returns -1 with errno set to EINTR, then it has not changed
any of the fd_sets. You can't start looking at them.

When clearing a descriptor, the code has the usual select off by one
error when setting sync_io_nfds.

I don't see how this code could ever have worked correctly.

I have appended a patch for the problems I found.

Files:

• c/src/exec/score/cpu/unix/cpu.c (modified) (2 diffs)
• cpukit/score/cpu/unix/cpu.c (modified) (2 diffs)

c/src/exec/score/cpu/unix/cpu.c

@@ -401 +401 @@
     if (sync_io_nfds) {
       int result;
-
+      fd_set readfds, writefds, exceptfds;
+
+      readfds = sync_io_readfds;
+      writefds = sync_io_writefds;
+      exceptfds = sync_io_exceptfds;
       result = select(sync_io_nfds,
-                 &sync_io_readfds,
-                 &sync_io_writefds,
-                 &sync_io_exceptfds,
+                 &readfds,
+                 &writefds,
+                 &exceptfds,
                  NULL);
 
-      if ((result < 0) && (errno != EINTR))
-        _CPU_Fatal_error(0x200);       /* FIXME : what number should go here !! */
+      if (result < 0) {
+        if (errno != EINTR)
+          _CPU_Fatal_error(0x200);       /* FIXME : what number should go here !! */
+        _Thread_Dispatch();
+        continue;
+      }
 
       for (fd = 0; fd < sync_io_nfds; fd++) {
-        boolean read = FD_ISSET(fd, &sync_io_readfds);
-        boolean write = FD_ISSET(fd, &sync_io_writefds);
-        boolean except = FD_ISSET(fd, &sync_io_exceptfds);
+        boolean read = FD_ISSET(fd, &readfds);
+        boolean write = FD_ISSET(fd, &writefds);
+        boolean except = FD_ISSET(fd, &exceptfds);
 
         if (_CPU_Sync_io_handlers[fd] && (read || write || except))
           _CPU_Sync_io_handlers[fd](fd, read, write, except);
-
-        _Thread_Dispatch();
       }
+
+      _Thread_Dispatch();
     } else
       pause();
@@ -870 +878 @@
           FD_ISSET(fd, &sync_io_writefds) ||
           FD_ISSET(fd, &sync_io_exceptfds))
-        sync_io_nfds = fd;
+        sync_io_nfds = fd + 1;
     return 0;
   }

cpukit/score/cpu/unix/cpu.c

@@ -401 +401 @@
     if (sync_io_nfds) {
       int result;
-
+      fd_set readfds, writefds, exceptfds;
+
+      readfds = sync_io_readfds;
+      writefds = sync_io_writefds;
+      exceptfds = sync_io_exceptfds;
       result = select(sync_io_nfds,
-                 &sync_io_readfds,
-                 &sync_io_writefds,
-                 &sync_io_exceptfds,
+                 &readfds,
+                 &writefds,
+                 &exceptfds,
                  NULL);
 
-      if ((result < 0) && (errno != EINTR))
-        _CPU_Fatal_error(0x200);       /* FIXME : what number should go here !! */
+      if (result < 0) {
+        if (errno != EINTR)
+          _CPU_Fatal_error(0x200);       /* FIXME : what number should go here !! */
+        _Thread_Dispatch();
+        continue;
+      }
 
       for (fd = 0; fd < sync_io_nfds; fd++) {
-        boolean read = FD_ISSET(fd, &sync_io_readfds);
-        boolean write = FD_ISSET(fd, &sync_io_writefds);
-        boolean except = FD_ISSET(fd, &sync_io_exceptfds);
+        boolean read = FD_ISSET(fd, &readfds);
+        boolean write = FD_ISSET(fd, &writefds);
+        boolean except = FD_ISSET(fd, &exceptfds);
 
         if (_CPU_Sync_io_handlers[fd] && (read || write || except))
           _CPU_Sync_io_handlers[fd](fd, read, write, except);
-
-        _Thread_Dispatch();
       }
+
+      _Thread_Dispatch();
     } else
       pause();
@@ -870 +878 @@
           FD_ISSET(fd, &sync_io_writefds) ||
           FD_ISSET(fd, &sync_io_exceptfds))
-        sync_io_nfds = fd;
+        sync_io_nfds = fd + 1;
     return 0;
   }