clone: prepare to recycle CLONE_STOPPED

Ulrich says that we never used this clone flags and that nothing should be
using it.

As we're down to only a single bit left in clone's flags argument, let's add a
warning to check that no userspace is actually using it.  Hopefully we will
be able to recycle it.

Roland said:

  CLONE_STOPPED was previously used by some NTPL versions when under
  thread_db (i.e.  only when being actively debugged by gdb), but not for a
  long time now, and it never worked reliably when it was used.  Removing it
  seems fine to me.

[akpm@linux-foundation.org: it looks like CLONE_DETACHED is being used]
Cc: Ulrich Drepper <drepper@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 17 insertions, 0 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index 05e0b6f4365..6caf4f23206 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1450,6 +1450,23 @@ long do_fork(unsigned long clone_flags,
         int trace = 0;
         long nr;
 
+        /*
+         * We hope to recycle these flags after 2.6.26
+         */
+        if (unlikely(clone_flags & CLONE_STOPPED)) {
+                static int __read_mostly count = 100;
+
+                if (count > 0 && printk_ratelimit()) {
+                        char comm[TASK_COMM_LEN];
+
+                        count--;
+                        printk(KERN_INFO "fork(): process `%s' used deprecated "
+                                        "clone flags 0x%lx\n",
+                                get_task_comm(comm, current),
+                                clone_flags & CLONE_STOPPED);
+                }
+        }
+
         if (unlikely(current->ptrace)) {
                 trace = fork_traceflag (clone_flags);
                 if (trace)