From d21b96c8ed2aea7e6b7bf4735e1d2503cfbf4072 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Thu, 19 Nov 2020 13:14:40 +0100
Subject: [PATCH] ALSA: mixart: Fix mutex deadlock
Git-commit: d21b96c8ed2aea7e6b7bf4735e1d2503cfbf4072
Patch-mainline: v5.10-rc5
References: git-fixes

The code change for switching to non-atomic mode brought the
unexpected mutex deadlock in get_msg().  It converted the spinlock
with the existing mutex, but there were calls with the already holding
the mutex.  Since the only place that needs the extra lock is the code
path from snd_mixart_send_msg(), remove the mutex lock in get_msg()
and apply in the caller side for fixing the mutex deadlock.

Fixes: 8d3a8b5cb57d ("ALSA: mixart: Use nonatomic PCM ops")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20201119121440.18945-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

---
 sound/pci/mixart/mixart_core.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/sound/pci/mixart/mixart_core.c b/sound/pci/mixart/mixart_core.c
index 0bdd33b0af65..fb8895af0363 100644
--- a/sound/pci/mixart/mixart_core.c
+++ b/sound/pci/mixart/mixart_core.c
@@ -70,7 +70,6 @@ static int get_msg(struct mixart_mgr *mgr, struct mixart_msg *resp,
 	unsigned int i;
 #endif
 
-	mutex_lock(&mgr->msg_lock);
 	err = 0;
 
 	/* copy message descriptor from miXart to driver */
@@ -119,8 +118,6 @@ static int get_msg(struct mixart_mgr *mgr, struct mixart_msg *resp,
 	writel_be(headptr, MIXART_MEM(mgr, MSG_OUTBOUND_FREE_HEAD));
 
  _clean_exit:
-	mutex_unlock(&mgr->msg_lock);
-
 	return err;
 }
 
@@ -258,7 +255,9 @@ int snd_mixart_send_msg(struct mixart_mgr *mgr, struct mixart_msg *request, int
 	resp.data = resp_data;
 	resp.size = max_resp_size;
 
+	mutex_lock(&mgr->msg_lock);
 	err = get_msg(mgr, &resp, msg_frame);
+	mutex_unlock(&mgr->msg_lock);
 
 	if( request->message_id != resp.message_id )
 		dev_err(&mgr->pci->dev, "RESPONSE ERROR!\n");
-- 
2.16.4