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authorRoland McGrath <roland@redhat.com>2008-03-24 18:36:23 -0700
committerRoland McGrath <roland@redhat.com>2008-07-16 18:02:33 -0700
commitf470021adb9190819c03d6d8c5c860a17480aa6d (patch)
tree9e5c2808138624e272b562a502cfd035ae59c268 /kernel/ptrace.c
parent98abed02007b19bbfd68b6d06a5485afc3eeb01b (diff)
downloadlinux-2.6.34-ux500-f470021adb9190819c03d6d8c5c860a17480aa6d.tar.gz
ptrace children revamp
ptrace no longer fiddles with the children/sibling links, and the old ptrace_children list is gone. Now ptrace, whether of one's own children or another's via PTRACE_ATTACH, just uses the new ptraced list instead. There should be no user-visible difference that matters. The only change is the order in which do_wait() sees multiple stopped children and stopped ptrace attachees. Since wait_task_stopped() was changed earlier so it no longer reorders the children list, we already know this won't cause any new problems. Signed-off-by: Roland McGrath <roland@redhat.com>
Diffstat (limited to 'kernel/ptrace.c')
-rw-r--r--kernel/ptrace.c37
1 files changed, 24 insertions, 13 deletions
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index e337390fce0..8392a9da645 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -33,13 +33,9 @@
*/
void __ptrace_link(struct task_struct *child, struct task_struct *new_parent)
{
- BUG_ON(!list_empty(&child->ptrace_list));
- if (child->parent == new_parent)
- return;
- list_add(&child->ptrace_list, &child->parent->ptrace_children);
- remove_parent(child);
+ BUG_ON(!list_empty(&child->ptrace_entry));
+ list_add(&child->ptrace_entry, &new_parent->ptraced);
child->parent = new_parent;
- add_parent(child);
}
/*
@@ -73,12 +69,8 @@ void __ptrace_unlink(struct task_struct *child)
BUG_ON(!child->ptrace);
child->ptrace = 0;
- if (ptrace_reparented(child)) {
- list_del_init(&child->ptrace_list);
- remove_parent(child);
- child->parent = child->real_parent;
- add_parent(child);
- }
+ child->parent = child->real_parent;
+ list_del_init(&child->ptrace_entry);
if (task_is_traced(child))
ptrace_untrace(child);
@@ -492,15 +484,34 @@ int ptrace_traceme(void)
/*
* Are we already being traced?
*/
+repeat:
task_lock(current);
if (!(current->ptrace & PT_PTRACED)) {
+ /*
+ * See ptrace_attach() comments about the locking here.
+ */
+ unsigned long flags;
+ if (!write_trylock_irqsave(&tasklist_lock, flags)) {
+ task_unlock(current);
+ do {
+ cpu_relax();
+ } while (!write_can_lock(&tasklist_lock));
+ goto repeat;
+ }
+
ret = security_ptrace(current->parent, current,
PTRACE_MODE_ATTACH);
+
/*
* Set the ptrace bit in the process ptrace flags.
+ * Then link us on our parent's ptraced list.
*/
- if (!ret)
+ if (!ret) {
current->ptrace |= PT_PTRACED;
+ __ptrace_link(current, current->real_parent);
+ }
+
+ write_unlock_irqrestore(&tasklist_lock, flags);
}
task_unlock(current);
return ret;