Add another trivial helper for the sake of grep. It also auto-documents the
fact that ->parent != real_parent implies ->ptrace.
No functional changes.
Signed-off-by: Oleg Nesterov <[email protected]>
--- 25/include/linux/ptrace.h~5_PR 2008-02-17 23:40:09.000000000 +0300
+++ 25/include/linux/ptrace.h 2008-03-03 06:22:15.000000000 +0300
@@ -98,6 +98,10 @@ extern void ptrace_untrace(struct task_s
extern int ptrace_may_attach(struct task_struct *task);
extern int __ptrace_may_attach(struct task_struct *task);
+static inline int ptrace_reparented(struct task_struct *child)
+{
+ return child->real_parent != child->parent;
+}
static inline void ptrace_link(struct task_struct *child,
struct task_struct *new_parent)
{
--- 25/kernel/exit.c~5_PR 2008-03-03 05:43:17.000000000 +0300
+++ 25/kernel/exit.c 2008-03-03 06:24:56.000000000 +0300
@@ -629,7 +629,7 @@ reparent_thread(struct task_struct *p, s
if (unlikely(traced)) {
/* Preserve ptrace links if someone else is tracing this child. */
list_del_init(&p->ptrace_list);
- if (p->parent != p->real_parent)
+ if (ptrace_reparented(p))
list_add(&p->ptrace_list, &p->real_parent->ptrace_children);
} else {
/* If this child is being traced, then we're the one tracing it
@@ -796,8 +796,8 @@ static void exit_notify(struct task_stru
* only has special meaning to our real parent.
*/
if (!task_detached(tsk) && thread_group_empty(tsk)) {
- int signal = (tsk->parent == tsk->real_parent)
- ? tsk->exit_signal : SIGCHLD;
+ int signal = ptrace_reparented(tsk) ?
+ SIGCHLD : tsk->exit_signal;
do_notify_parent(tsk, signal);
} else if (tsk->ptrace) {
do_notify_parent(tsk, SIGCHLD);
@@ -1198,8 +1198,7 @@ static int wait_task_zombie(struct task_
return 0;
}
- /* traced means p->ptrace, but not vice versa */
- traced = (p->real_parent != p->parent);
+ traced = ptrace_reparented(p);
if (likely(!traced)) {
struct signal_struct *psig;
Somehow the patch I sent misses the change in ptrace.c, it can use the
new helper too.
[PATCH 2/2] introduce ptrace_reparented() helper
Add another trivial helper for the sake of grep. It also auto-documents the
fact that ->parent != real_parent implies ->ptrace.
No functional changes.
Signed-off-by: Oleg Nesterov <[email protected]>
--- 25/include/linux/ptrace.h~5_PR 2008-02-17 23:40:09.000000000 +0300
+++ 25/include/linux/ptrace.h 2008-03-03 06:22:15.000000000 +0300
@@ -98,6 +98,10 @@ extern void ptrace_untrace(struct task_s
extern int ptrace_may_attach(struct task_struct *task);
extern int __ptrace_may_attach(struct task_struct *task);
+static inline int ptrace_reparented(struct task_struct *child)
+{
+ return child->real_parent != child->parent;
+}
static inline void ptrace_link(struct task_struct *child,
struct task_struct *new_parent)
{
--- 25/kernel/exit.c~5_PR 2008-03-03 05:43:17.000000000 +0300
+++ 25/kernel/exit.c 2008-03-03 06:24:56.000000000 +0300
@@ -629,7 +629,7 @@ reparent_thread(struct task_struct *p, s
if (unlikely(traced)) {
/* Preserve ptrace links if someone else is tracing this child. */
list_del_init(&p->ptrace_list);
- if (p->parent != p->real_parent)
+ if (ptrace_reparented(p))
list_add(&p->ptrace_list, &p->real_parent->ptrace_children);
} else {
/* If this child is being traced, then we're the one tracing it
@@ -796,8 +796,8 @@ static void exit_notify(struct task_stru
* only has special meaning to our real parent.
*/
if (!task_detached(tsk) && thread_group_empty(tsk)) {
- int signal = (tsk->parent == tsk->real_parent)
- ? tsk->exit_signal : SIGCHLD;
+ int signal = ptrace_reparented(tsk) ?
+ SIGCHLD : tsk->exit_signal;
do_notify_parent(tsk, signal);
} else if (tsk->ptrace) {
do_notify_parent(tsk, SIGCHLD);
@@ -1198,8 +1198,7 @@ static int wait_task_zombie(struct task_
return 0;
}
- /* traced means p->ptrace, but not vice versa */
- traced = (p->real_parent != p->parent);
+ traced = ptrace_reparented(p);
if (likely(!traced)) {
struct signal_struct *psig;
--- 25/kernel/ptrace.c~5_PR 2008-02-17 23:40:09.000000000 +0300
+++ 25/kernel/ptrace.c 2008-03-03 06:23:43.000000000 +0300
@@ -73,7 +73,7 @@ void __ptrace_unlink(struct task_struct
BUG_ON(!child->ptrace);
child->ptrace = 0;
- if (!list_empty(&child->ptrace_list)) {
+ if (ptrace_reparented(child)) {
list_del_init(&child->ptrace_list);
remove_parent(child);
child->parent = child->real_parent;
> Somehow the patch I sent misses the change in ptrace.c, it can use the
> new helper too.
Actually, my pedantic streak prefers that to be in a separate patch.
I think the ptrace_reparented cleanup is fine, it is purely cosmetic and
improves readability.
> - if (!list_empty(&child->ptrace_list)) {
> + if (ptrace_reparented(child)) {
This is changing the test from list_empty(&child->ptrace_list)
to child->parent == child->real_parent. It should indeed be
impossible for those tests not to match. But, paranoia is its
own reward. I don't object to the change, but it should be
separate so bisect distinguishes it should it ever turn out to
matter in some way we are now overlooking. I'd even be a
little inclined towards:
if (child->real_parent == child->parent) {
BUG_ON(!list_empty(&child->ptrace_list));
return 0;
} else {
BUG_ON(list_empty(&child->ptrace_list));
return 1;
}
except of course you couldn't use that in the reparent_thread case.
Thanks,
Roland
On 03/04, Roland McGrath wrote:
>
> > Somehow the patch I sent misses the change in ptrace.c, it can use the
> > new helper too.
>
> Actually, my pedantic streak prefers that to be in a separate patch.
> ...
> I don't object to the change, but it should be
> separate so bisect distinguishes it should it ever turn out to
> matter in some way we are now overlooking.
OK, agreed, will do.
> I'd even be a
> little inclined towards:
>
> if (child->real_parent == child->parent) {
> BUG_ON(!list_empty(&child->ptrace_list));
> return 0;
> } else {
> BUG_ON(list_empty(&child->ptrace_list));
> return 1;
> }
>
> except of course you couldn't use that in the reparent_thread case.
^^^^^^^^^^^^^^^
I can't believe. You are reading my mind!
I am planning to do some changes in forget_original_parent (fix 2 very
old minor bugs and _perhaps_ add some improvement). I hit the minor but
nasty problem: this open coded __ptrace_unlink() in reparent_thread().
_This_ is the actual reason for this patch.
So. Would you object if I do
--- kernel/ptrace.c 2008-03-03 17:01:06.000000000 +0300
+++ kernel/ptrace.c 2008-03-05 20:22:44.801142777 +0300
@@ -67,11 +67,12 @@ void ptrace_untrace(struct task_struct *
* remove it from the ptrace list.
*
* Must be called with the tasklist lock write-held.
+ *
+ * Either the caller is ptracer, or the caller is ->real_parent
+ * and the child is not traced.
*/
void __ptrace_unlink(struct task_struct *child)
{
- BUG_ON(!child->ptrace);
-
child->ptrace = 0;
if (ptrace_reparented(child)) {
list_del_init(&child->ptrace_list);
?
Oleg.
> I am planning to do some changes in forget_original_parent (fix 2 very
> old minor bugs and _perhaps_ add some improvement). I hit the minor but
> nasty problem: this open coded __ptrace_unlink() in reparent_thread().
> _This_ is the actual reason for this patch.
>
> So. Would you object if I do
>
> --- kernel/ptrace.c 2008-03-03 17:01:06.000000000 +0300
> +++ kernel/ptrace.c 2008-03-05 20:22:44.801142777 +0300
> @@ -67,11 +67,12 @@ void ptrace_untrace(struct task_struct *
> * remove it from the ptrace list.
> *
> * Must be called with the tasklist lock write-held.
> + *
> + * Either the caller is ptracer, or the caller is ->real_parent
> + * and the child is not traced.
> */
> void __ptrace_unlink(struct task_struct *child)
> {
> - BUG_ON(!child->ptrace);
> -
> child->ptrace = 0;
> if (ptrace_reparented(child)) {
> list_del_init(&child->ptrace_list);
>
> ?
That seems ok. The duplication of magic in reparent_thread is indeed bad.
I don't think this BUG_ON is buying us much if we haven't hit it in a long
time.
Thanks,
Roland