Change 33492 did not spread the protection wide enough. There were

[perl5.git] / perlio.c

diff --git a/perlio.c b/perlio.c
index d0f51d5..ed829e4 100644 (file)
--- a/perlio.c
+++ b/perlio.c
@@ -3130,7 +3130,7 @@ PerlIOStdio_close(pTHX_ PerlIO *f)
        int invalidate = 0;
        IV result = 0;
        int saveerr = 0;
-       int dupfd = 0;
+       int dupfd = -1;
 #ifdef SOCKS5_VERSION_NAME
        /* Socks lib overrides close() but stdio isn't linked to
           that library (though we are) - so we must call close()
@@ -3156,8 +3156,37 @@ PerlIOStdio_close(pTHX_ PerlIO *f)
            result = PerlIO_flush(f);
            saveerr = errno;
            invalidate = PerlIOStdio_invalidate_fileno(aTHX_ stdio);
-           if (!invalidate)
+           if (!invalidate) {
+#ifdef USE_ITHREADS
+               MUTEX_LOCK(&PL_perlio_mutex);
+               /* Right. We need a mutex here because for a brief while we will
+                  have the situation that fd is actually closed. Hence if a
+                  second thread were to get into this block, its dup() would
+                  likely return our fd as its dupfd. (after all, it is closed).
+                  Then if we get to the dup2() first, we blat the fd back
+                  (messing up its temporary as a side effect) only for it to
+                  then close its dupfd (== our fd) in its close(dupfd) */
+
+               /* There is, of course, a race condition, that any other thread
+                  trying to input/output/whatever on this fd will be stuffed
+                  for the duraction of this little manoeuver. Perhaps we should
+                  hold an IO mutex for the duration of every IO operation if
+                  we know that invalidate doesn't work on this platform, but
+                  that would suck, and could kill performance.
+
+                  Except that correctness trumps speed.
+                  Advice from klortho #11912. */
+#endif
                dupfd = PerlLIO_dup(fd);
+#ifdef USE_ITHREADS
+               if (dupfd < 0) {
+                   MUTEX_UNLOCK(&PL_perlio_mutex);
+                   /* Oh cXap. This isn't going to go well. Not sure if we can
+                      recover from here, or if closing this particular FILE *
+                      is a good idea now.  */
+               }
+#endif
+           }
        }
         result = PerlSIO_fclose(stdio);
        /* We treat error from stdio as success if we invalidated
@@ -3171,9 +3200,12 @@ PerlIOStdio_close(pTHX_ PerlIO *f)
        /* in SOCKS' case, let close() determine return value */
        result = close(fd);
 #endif
-       if (dupfd) {
+       if (dupfd >= 0) {
            PerlLIO_dup2(dupfd,fd);
            PerlLIO_close(dupfd);
+#ifdef USE_ITHREADS
+           MUTEX_UNLOCK(&PL_perlio_mutex);
+#endif
        }
        return result;
     }