[RFC PATCH v1.1 09/11] mm/damon/core: wait ctx stop in damon_call() before reruning an error

[SJ Park]

damon_call() failure means the DAMON context started its termination.
The termination is asynchronously done in kdamond thread.  The caller's
error handling should handle the race, too.  It is complicated and easy
to make mistakes.

Update damon_call() to ensure the context is stopped in the case, by
waiting until the completion is confirmed.

Signed-off-by: SJ Park <sj@xxxxxxxxxx>
---
 mm/damon/core.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/mm/damon/core.c b/mm/damon/core.c
index 08510bf9b38da..390e00b3685ef 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -2010,6 +2010,8 @@ int damon_kdamond_pid(struct damon_ctx *ctx)
  * @ctx has succeeded.  Otherwise, this function could fall into an indefinite
  * wait.
  *
+ * When this function is failed, the @ctx is guaranteed to be stopped.
+ *
  * Return: 0 on success, negative error code otherwise.
  */
 int damon_call(struct damon_ctx *ctx, struct damon_call_control *control)
@@ -2022,7 +2024,7 @@ int damon_call(struct damon_ctx *ctx, struct damon_call_control *control)
 	mutex_lock(&ctx->call_controls_lock);
 	if (ctx->call_controls_obsolete) {
 		mutex_unlock(&ctx->call_controls_lock);
-		return -ECANCELED;
+		goto canceled;
 	}
 	list_add_tail(&control->list, &ctx->call_controls);
 	mutex_unlock(&ctx->call_controls_lock);
@@ -2030,8 +2032,14 @@ int damon_call(struct damon_ctx *ctx, struct damon_call_control *control)
 		return 0;
 	wait_for_completion(&control->completion);
 	if (control->canceled)
-		return -ECANCELED;
+		goto canceled;
 	return 0;
+
+canceled:
+	while (damon_is_running(ctx))
+		schedule_timeout_idle(msecs_to_jiffies(100));
+	return -ECANCELED;
+
 }
 
 /**
-- 
2.47.3