KTHREAD_SHOULD_PARK,
};
-static inline void set_kthread_struct(void *kthread)
+static inline struct kthread *to_kthread(struct task_struct *k)
+{
+ WARN_ON(!(k->flags & PF_KTHREAD));
+ return (__force void *)k->set_child_tid;
+}
+
+/*
+ * Variant of to_kthread() that doesn't assume @p is a kthread.
+ *
+ * Per construction; when:
+ *
+ * (p->flags & PF_KTHREAD) && p->set_child_tid
+ *
+ * the task is both a kthread and struct kthread is persistent. However
+ * PF_KTHREAD on it's own is not, kernel_thread() can exec() (See umh.c and
+ * begin_new_exec()).
+ */
+static inline struct kthread *__to_kthread(struct task_struct *p)
+{
+ void *kthread = (__force void *)p->set_child_tid;
+ if (kthread && !(p->flags & PF_KTHREAD))
+ kthread = NULL;
+ return kthread;
+}
+
+void set_kthread_struct(struct task_struct *p)
{
+ struct kthread *kthread;
+
+ if (__to_kthread(p))
+ return;
+
+ kthread = kzalloc(sizeof(*kthread), GFP_KERNEL);
/*
* 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 inline struct kthread *to_kthread(struct task_struct *k)
-{
- WARN_ON(!(k->flags & PF_KTHREAD));
- return (__force void *)k->set_child_tid;
+ p->set_child_tid = (__force void __user *)kthread;
}
void free_kthread_struct(struct task_struct *k)
*/
void *kthread_func(struct task_struct *task)
{
- if (task->flags & PF_KTHREAD)
- return to_kthread(task)->threadfn;
+ struct kthread *kthread = __to_kthread(task);
+ if (kthread)
+ return kthread->threadfn;
return NULL;
}
EXPORT_SYMBOL_GPL(kthread_func);
*/
void *kthread_probe_data(struct task_struct *task)
{
- struct kthread *kthread = to_kthread(task);
+ struct kthread *kthread = __to_kthread(task);
void *data = NULL;
- copy_from_kernel_nofault(&data, &kthread->data, sizeof(data));
+ if (kthread)
+ copy_from_kernel_nofault(&data, &kthread->data, sizeof(data));
return data;
}
struct kthread *self;
int ret;
- self = kzalloc(sizeof(*self), GFP_KERNEL);
- set_kthread_struct(self);
+ set_kthread_struct(current);
+ self = to_kthread(current);
/* If user was SIGKILLed, I release the structure. */
done = xchg(&create->done, NULL);
}
EXPORT_SYMBOL(kthread_create_on_node);
-static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, long state)
+static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, unsigned int state)
{
unsigned long flags;
raw_spin_unlock_irqrestore(&p->pi_lock, flags);
}
-static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
+static void __kthread_bind(struct task_struct *p, unsigned int cpu, unsigned int state)
{
__kthread_bind_mask(p, cpumask_of(cpu), state);
}
set_bit(KTHREAD_IS_PER_CPU, &kthread->flags);
}
-bool kthread_is_per_cpu(struct task_struct *k)
+bool kthread_is_per_cpu(struct task_struct *p)
{
- struct kthread *kthread = to_kthread(k);
+ struct kthread *kthread = __to_kthread(p);
if (!kthread)
return false;
EXPORT_SYMBOL_GPL(kthread_flush_work);
/*
- * This function removes the work from the worker queue. Also it makes sure
- * that it won't get queued later via the delayed work's timer.
+ * Make sure that the timer is neither set nor running and could
+ * not manipulate the work list_head any longer.
+ *
+ * The function is called under worker->lock. The lock is temporary
+ * released but the timer can't be set again in the meantime.
+ */
+static void kthread_cancel_delayed_work_timer(struct kthread_work *work,
+ unsigned long *flags)
+{
+ struct kthread_delayed_work *dwork =
+ container_of(work, struct kthread_delayed_work, work);
+ struct kthread_worker *worker = work->worker;
+
+ /*
+ * del_timer_sync() must be called to make sure that the timer
+ * callback is not running. The lock must be temporary released
+ * to avoid a deadlock with the callback. In the meantime,
+ * any queuing is blocked by setting the canceling counter.
+ */
+ work->canceling++;
+ raw_spin_unlock_irqrestore(&worker->lock, *flags);
+ del_timer_sync(&dwork->timer);
+ raw_spin_lock_irqsave(&worker->lock, *flags);
+ work->canceling--;
+}
+
+/*
+ * This function removes the work from the worker queue.
+ *
+ * It is called under worker->lock. The caller must make sure that
+ * the timer used by delayed work is not running, e.g. by calling
+ * kthread_cancel_delayed_work_timer().
*
* The work might still be in use when this function finishes. See the
* current_work proceed by the worker.
* Return: %true if @work was pending and successfully canceled,
* %false if @work was not pending
*/
-static bool __kthread_cancel_work(struct kthread_work *work, bool is_dwork,
- unsigned long *flags)
+static bool __kthread_cancel_work(struct kthread_work *work)
{
- /* Try to cancel the timer if exists. */
- if (is_dwork) {
- struct kthread_delayed_work *dwork =
- container_of(work, struct kthread_delayed_work, work);
- struct kthread_worker *worker = work->worker;
-
- /*
- * del_timer_sync() must be called to make sure that the timer
- * callback is not running. The lock must be temporary released
- * to avoid a deadlock with the callback. In the meantime,
- * any queuing is blocked by setting the canceling counter.
- */
- work->canceling++;
- raw_spin_unlock_irqrestore(&worker->lock, *flags);
- del_timer_sync(&dwork->timer);
- raw_spin_lock_irqsave(&worker->lock, *flags);
- work->canceling--;
- }
-
/*
* Try to remove the work from a worker list. It might either
* be from worker->work_list or from worker->delayed_work_list.
* modify @dwork's timer so that it expires after @delay. If @delay is zero,
* @work is guaranteed to be queued immediately.
*
- * Return: %true if @dwork was pending and its timer was modified,
- * %false otherwise.
+ * Return: %false if @dwork was idle and queued, %true otherwise.
*
* A special case is when the work is being canceled in parallel.
* It might be caused either by the real kthread_cancel_delayed_work_sync()
* or yet another kthread_mod_delayed_work() call. We let the other command
- * win and return %false here. The caller is supposed to synchronize these
- * operations a reasonable way.
+ * win and return %true here. The return value can be used for reference
+ * counting and the number of queued works stays the same. Anyway, the caller
+ * is supposed to synchronize these operations a reasonable way.
*
* This function is safe to call from any context including IRQ handler.
* See __kthread_cancel_work() and kthread_delayed_work_timer_fn()
{
struct kthread_work *work = &dwork->work;
unsigned long flags;
- int ret = false;
+ int ret;
raw_spin_lock_irqsave(&worker->lock, flags);
/* Do not bother with canceling when never queued. */
- if (!work->worker)
+ if (!work->worker) {
+ ret = false;
goto fast_queue;
+ }
/* Work must not be used with >1 worker, see kthread_queue_work() */
WARN_ON_ONCE(work->worker != worker);
- /* Do not fight with another command that is canceling this work. */
- if (work->canceling)
+ /*
+ * Temporary cancel the work but do not fight with another command
+ * that is canceling the work as well.
+ *
+ * It is a bit tricky because of possible races with another
+ * mod_delayed_work() and cancel_delayed_work() callers.
+ *
+ * The timer must be canceled first because worker->lock is released
+ * when doing so. But the work can be removed from the queue (list)
+ * only when it can be queued again so that the return value can
+ * be used for reference counting.
+ */
+ kthread_cancel_delayed_work_timer(work, &flags);
+ if (work->canceling) {
+ /* The number of works in the queue does not change. */
+ ret = true;
goto out;
+ }
+ ret = __kthread_cancel_work(work);
- ret = __kthread_cancel_work(work, true, &flags);
fast_queue:
__kthread_queue_delayed_work(worker, dwork, delay);
out:
/* Work must not be used with >1 worker, see kthread_queue_work(). */
WARN_ON_ONCE(work->worker != worker);
- ret = __kthread_cancel_work(work, is_dwork, &flags);
+ if (is_dwork)
+ kthread_cancel_delayed_work_timer(work, &flags);
+
+ ret = __kthread_cancel_work(work);
if (worker->current_work != work)
goto out_fast;