r6090: Patch to fix sys_select so it can't drop signals if another fd

is ready to read. Patch from Mark Weaver <mark-clist@npsl.co.uk>.
The only question is, how did we miss this for so long..... :-).
Jeremy.

diff --git a/source/lib/select.c b/source/lib/select.c
index f3d119bdb153e488a41b70af359547adae7e0de4..2e55f9753dbea30d8deed99fd2eb288f1d967c41 100644 (file)
--- a/source/lib/select.c
+++ b/source/lib/select.c
@@ -99,20 +99,23 @@ int sys_select(int maxfd, fd_set *readfds, fd_set *writefds, fd_set *errorfds, s
                        FD_ZERO(writefds);
                if (errorfds)
                        FD_ZERO(errorfds);
-       }
-
-       if (FD_ISSET(select_pipe[0], readfds2)) {
+       } else if (FD_ISSET(select_pipe[0], readfds2)) {
                char c;
                saved_errno = errno;
                if (read(select_pipe[0], &c, 1) == 1) {
                        pipe_read++;
-               }
-               errno = saved_errno;
-               FD_CLR(select_pipe[0], readfds2);
-               ret--;
-               if (ret == 0) {
+                       /* Mark Weaver <mark-clist@npsl.co.uk> pointed out a critical
+                          fix to ensure we don't lose signals. We must always
+                          return -1 when the select pipe is set, otherwise if another
+                          fd is also ready (so ret == 2) then we used to eat the
+                          byte in the pipe and lose the signal. JRA.
+                       */
                        ret = -1;
                        errno = EINTR;
+               } else {
+                       FD_CLR(select_pipe[0], readfds2);
+                       ret--;
+                       errno = saved_errno;
                }
        }
 
@@ -167,7 +170,12 @@ int sys_select_intr(int maxfd, fd_set *readfds, fd_set *writefds, fd_set *errorf
                        ptval->tv_usec = tdif % 1000000;
                }
 
-               ret = sys_select(maxfd, readfds2, writefds2, errorfds2, ptval);
+               /* We must use select and not sys_select here. If we use
+                  sys_select we'd lose the fact a signal occurred when sys_select
+                  read a byte from the pipe. Fix from Mark Weaver
+                  <mark-clist@npsl.co.uk>
+               */
+               ret = select(maxfd, readfds2, writefds2, errorfds2, ptval);
        } while (ret == -1 && errno == EINTR);
 
        if (readfds)