linux-kernel - [PATCH 30/32] staging: wfx: fix potential deadlock in wfx_tx

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Date:   Wed,  1 Apr 2020 13:04:03 +0200
From:   Jerome Pouiller <Jerome.Pouiller@...abs.com>
To:     devel@...verdev.osuosl.org, linux-wireless@...r.kernel.org
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S . Miller" <davem@...emloft.net>,
        Jérôme Pouiller 
        <jerome.pouiller@...abs.com>
Subject: [PATCH 30/32] staging: wfx: fix potential deadlock in wfx_tx_flush()

From: Jérôme Pouiller <jerome.pouiller@...abs.com>

wfx_tx_flush() wait there are no more frame in device buffer. However,
this event may never happens since wfx_tx_flush() don't forbid to
enqueue new frames.

Note that wfx_tx_flush() should only ensure that all frames currently in
hardware queues are sent. So the current code is more restrictive that
it should.

Note that wfx_tx_flush() release the lock before to return while
wfx_tx_lock_flush() keep the lock.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@...abs.com>
---
 drivers/staging/wfx/queue.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/staging/wfx/queue.c b/drivers/staging/wfx/queue.c
index d4302a30dc41..e6d7d0e45156 100644
--- a/drivers/staging/wfx/queue.c
+++ b/drivers/staging/wfx/queue.c
@@ -36,6 +36,7 @@ void wfx_tx_flush(struct wfx_dev *wdev)
 	if (wdev->chip_frozen)
 		return;
 
+	wfx_tx_lock(wdev);
 	mutex_lock(&wdev->hif_cmd.lock);
 	ret = wait_event_timeout(wdev->hif.tx_buffers_empty,
 				 !wdev->hif.tx_buffers_used,
@@ -54,6 +55,7 @@ void wfx_tx_flush(struct wfx_dev *wdev)
 		wdev->chip_frozen = 1;
 	}
 	mutex_unlock(&wdev->hif_cmd.lock);
+	wfx_tx_unlock(wdev);
 }
 
 void wfx_tx_lock_flush(struct wfx_dev *wdev)
-- 
2.25.1