From 9a85a89313b18fbfed2e966ff62f8efaea3f4b7f Mon Sep 17 00:00:00 2001
From: Krzysztof Chruscinski <krzysztof.chruscinski@nordicsemi.no>
Date: Tue, 6 Apr 2021 11:44:04 +0200
Subject: [PATCH] shell: logging: Fix assertion when shell is overflowed with
 logging

When shell had too many pending log messages it was attempting to
drop expired messages and retrying to put the new message. There
was an assumption that enough messages are dropped and new message
can be put. It may not be the case if no message expired during
given time. Wrapped the operation in loop to continue until expired
message is freed and new message is enqueued.

Signed-off-by: Krzysztof Chruscinski <krzysztof.chruscinski@nordicsemi.no>
---
 subsys/shell/shell_log_backend.c | 45 ++++++++++++++++----------------
 1 file changed, 23 insertions(+), 22 deletions(-)

diff --git a/subsys/shell/shell_log_backend.c b/subsys/shell/shell_log_backend.c
index 613e00285cf..9fa9fca6dc1 100644
--- a/subsys/shell/shell_log_backend.c
+++ b/subsys/shell/shell_log_backend.c
@@ -92,36 +92,37 @@ static void msg_to_fifo(const struct shell *shell,
 			struct log_msg *msg)
 {
 	int err;
+	bool cont;
 	struct shell_log_backend_msg t_msg = {
 		.msg = msg,
 		.timestamp = k_uptime_get_32()
 	};
 
-	err = k_msgq_put(shell->log_backend->msgq, &t_msg,
-			 K_MSEC(shell->log_backend->timeout));
+	do {
+		cont = false;
+		err = k_msgq_put(shell->log_backend->msgq, &t_msg,
+				 K_MSEC(shell->log_backend->timeout));
 
-	switch (err) {
-	case 0:
-		break;
-	case -EAGAIN:
-	case -ENOMSG:
-	{
-		flush_expired_messages(shell);
+		switch (err) {
+		case 0:
+			break;
+		case -EAGAIN:
+		case -ENOMSG:
+		{
+			/* Attempt to drop old message. */
+			flush_expired_messages(shell);
 
-		err = k_msgq_put(shell->log_backend->msgq, &msg, K_NO_WAIT);
-		if (err) {
-			/* Unexpected case as we just freed one element and
-			 * there is no other context that puts into the msgq.
-			 */
-			__ASSERT_NO_MSG(0);
+			/* Retry putting message. */
+			cont = true;
+
+			break;
 		}
-		break;
-	}
-	default:
-		/* Other errors are not expected. */
-		__ASSERT_NO_MSG(0);
-		break;
-	}
+		default:
+			/* Other errors are not expected. */
+			__ASSERT_NO_MSG(0);
+			break;
+		}
+	} while (cont);
 }
 
 void z_shell_log_backend_disable(const struct shell_log_backend *backend)