On 06/28, Linus Torvalds wrote:
>
> Then try_get_task_stack(tsk) becomes
>
> void *try_get_task_stack(struct task_struct *tsk)
> {
> void *stack = tsk->stack;
> if (!atomic_inc_not_zero(&tsk->stackref))
> stack = NULL;
> return stack;
> }
Yes, and then we can trivilly fix the users of to_live_kthread().
So I'll wait for this change and send the simple fix on top of it.
Otherwise I'll send another ugly hack (see below).
Oleg.
---
diff --git a/include/linux/kthread.h b/include/linux/kthread.h
index e691b6a..7667bc62 100644
--- a/include/linux/kthread.h
+++ b/include/linux/kthread.h
@@ -37,6 +37,7 @@ struct task_struct *kthread_create_on_cpu(int
(*threadfn)(void *data),
__k; \
})
+void set_kthread_struct(void *kthread);
void kthread_bind(struct task_struct *k, unsigned int cpu);
void kthread_bind_mask(struct task_struct *k, const struct cpumask *mask);
int kthread_stop(struct task_struct *k);
diff --git a/kernel/fork.c b/kernel/fork.c
index 97122f9..8643248 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -326,6 +326,23 @@ void release_task_stack(struct task_struct *tsk)
#endif
}
+void set_kthread_struct(void *kthread)
+{
+ /*
+ * This is the ugly but simple hack we will hopefully remove soon.
+ * We abuse ->set_child_tid to avoid the new member and because it
+ * can't be wrongly copied by copy_process(). We also rely on fact
+ * that the caller can't exec, so PF_KTHREAD can't be cleared.
+ */
+ current->set_child_tid = (__force void __user *)kthread;
+}
+
+static void free_kthread_struct(struct task_struct *tsk)
+{
+ if (tsk->flags & PF_KTHREAD)
+ kfree((__force void *)tsk->set_child_tid); /* can be NULL */
+}
+
void free_task(struct task_struct *tsk)
{
#ifndef CONFIG_THREAD_INFO_IN_TASK
@@ -345,6 +362,7 @@ void free_task(struct task_struct *tsk)
ftrace_graph_exit_task(tsk);
put_seccomp_filter(tsk);
arch_release_task_struct(tsk);
+ free_kthread_struct(tsk);
free_task_struct(tsk);
}
EXPORT_SYMBOL(free_task);
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 9ff173d..3a4921f 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -181,14 +181,11 @@ static int kthread(void *_create)
int (*threadfn)(void *data) = create->threadfn;
void *data = create->data;
struct completion *done;
- struct kthread self;
+ struct kthread *self;
int ret;
- self.flags = 0;
- self.data = data;
- init_completion(&self.exited);
- init_completion(&self.parked);
- current->vfork_done = &self.exited;
+ self = kmalloc(sizeof(*self), GFP_KERNEL);
+ set_kthread_struct(self);
/* If user was SIGKILLed, I release the structure. */
done = xchg(&create->done, NULL);
@@ -196,6 +193,19 @@ static int kthread(void *_create)
kfree(create);
do_exit(-EINTR);
}
+
+ if (!self) {
+ create->result = ERR_PTR(-ENOMEM);
+ complete(done);
+ do_exit(-ENOMEM);
+ }
+
+ self->flags = 0;
+ self->data = data;
+ init_completion(&self->exited);
+ init_completion(&self->parked);
+ current->vfork_done = &self->exited;
+
/* OK, tell user we're spawned, wait for stop or wakeup */
__set_current_state(TASK_UNINTERRUPTIBLE);
create->result = current;
@@ -203,12 +213,10 @@ static int kthread(void *_create)
schedule();
ret = -EINTR;
-
- if (!test_bit(KTHREAD_SHOULD_STOP, &self.flags)) {
- __kthread_parkme(&self);
+ if (!test_bit(KTHREAD_SHOULD_STOP, &self->flags)) {
+ __kthread_parkme(self);
ret = threadfn(data);
}
- /* we can't just return, we must preserve "self" on stack */
do_exit(ret);
}
