* fork-child.c (fork_inferior): Fork instead of vfork if

PRE_TRACE_FUN is non-null.

2 files changed, 17 insertions, 4 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index f5f0574..b7c605d 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2004-11-29  Mark Kettenis  <kettenis@gnu.org>
+
+	* fork-child.c (fork_inferior): Fork instead of vfork if
+	PRE_TRACE_FUN is non-null.
+
 2004-11-24  Fred Fish  <fnf@specifixinc.com>
 
 	* rs6000-tdep.c (skip_prologue): Use line table info to skip over
diff --git a/gdb/fork-child.c b/gdb/fork-child.c
index 90580ba..718a3d2 100644
--- a/gdb/fork-child.c
+++ b/gdb/fork-child.c
@@ -274,10 +274,18 @@ fork_inferior (char *exec_file_arg, char *allargs, char **env,
   if (pre_trace_fun != NULL)
     (*pre_trace_fun) ();
 
-  /* Create the child process.  Note that the apparent call to vfork()
-     below *might* actually be a call to fork() due to the fact that
-     autoconf will ``#define vfork fork'' on certain platforms.  */
-  if (debug_fork)
+  /* Create the child process.  Since the child process is going to
+     exec(3) shortlty afterwards, try to reduce the overhead by
+     calling vfork(2).  However, if PRE_TRACE_FUN is non-null, it's
+     likely that this optimization won't work since there's too much
+     work to do between the vfork(2) and the exec(3).  This is known
+     to be the case on ttrace(2)-based HP-UX, where some handshaking
+     between parent and child needs to happen between fork(2) and
+     exec(2).  However, since the parent is suspended in the vforked
+     state, this doesn't work.  Also note that the vfork(2) call might
+     actually be a call to fork(2) due to the fact that autoconf will
+     ``#define vfork fork'' on certain platforms.  */
+  if (pre_trace_fun || debug_fork)
     pid = fork ();
   else
     pid = vfork ();