futex: Replace PF_EXITPIDONE with a state

[mirror_ubuntu-bionic-kernel.git] / include / linux / futex.h

diff --git a/include/linux/futex.h b/include/linux/futex.h
index bc4138b87035530021c86339fff9554b2935b617..35703ec3a2556e7e4e4e942e435749a8ead758ab 100644 (file)
--- a/include/linux/futex.h
+++ b/include/linux/futex.h
@@ -53,6 +53,10 @@ union futex_key {
 #define FUTEX_KEY_INIT (union futex_key) { .both = { .ptr = NULL } }
 
 #ifdef CONFIG_FUTEX
+enum {
+       FUTEX_STATE_OK,
+       FUTEX_STATE_DEAD,
+};
 
 static inline void futex_init_task(struct task_struct *tsk)
 {
@@ -62,6 +66,34 @@ static inline void futex_init_task(struct task_struct *tsk)
 #endif
        INIT_LIST_HEAD(&tsk->pi_state_list);
        tsk->pi_state_cache = NULL;
+       tsk->futex_state = FUTEX_STATE_OK;
+}
+
+/**
+ * futex_exit_done - Sets the tasks futex state to FUTEX_STATE_DEAD
+ * @tsk:       task to set the state on
+ *
+ * Set the futex exit state of the task lockless. The futex waiter code
+ * observes that state when a task is exiting and loops until the task has
+ * actually finished the futex cleanup. The worst case for this is that the
+ * waiter runs through the wait loop until the state becomes visible.
+ *
+ * This has two callers:
+ *
+ * - futex_mm_release() after the futex exit cleanup has been done
+ *
+ * - do_exit() from the recursive fault handling path.
+ *
+ * In case of a recursive fault this is best effort. Either the futex exit
+ * code has run already or not. If the OWNER_DIED bit has been set on the
+ * futex then the waiter can take it over. If not, the problem is pushed
+ * back to user space. If the futex exit code did not run yet, then an
+ * already queued waiter might block forever, but there is nothing which
+ * can be done about that.
+ */
+static inline void futex_exit_done(struct task_struct *tsk)
+{
+       tsk->futex_state = FUTEX_STATE_DEAD;
 }
 
 void futex_mm_release(struct task_struct *tsk);
@@ -71,6 +103,7 @@ long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
 #else
 static inline void futex_init_task(struct task_struct *tsk) { }
 static inline void futex_mm_release(struct task_struct *tsk) { }
+static inline void futex_exit_done(struct task_struct *tsk) { }
 #endif
 
 #endif