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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Dmitry Vyukov <dvyukov@google.com>,
        syzbot+4fc21a003c8332eb0bdd@syzkaller.appspotmail.com,
        Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>,
        Melissa Wen <melissa.srw@gmail.com>,
        Haneen Mohammed <hamohammed.sa@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        David Airlie <airlied@linux.ie>,
        dri-devel@lists.freedesktop.org, Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.10 149/299] drm/vkms: fix misuse of WARN_ON
Date:   Mon, 10 May 2021 12:19:06 +0200
Message-Id: <20210510102009.882015233@linuxfoundation.org>
In-Reply-To: <20210510102004.821838356@linuxfoundation.org>
References: <20210510102004.821838356@linuxfoundation.org>
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From: Dmitry Vyukov <dvyukov@google.com>

[ Upstream commit b4142fc4d52d051d4d8df1fb6c569e5b445d369e ]

vkms_vblank_simulate() uses WARN_ON for timing-dependent condition
(timer overrun). This is a mis-use of WARN_ON, WARN_ON must be used
to denote kernel bugs. Use pr_warn() instead.

Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Reported-by: syzbot+4fc21a003c8332eb0bdd@syzkaller.appspotmail.com
Cc: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
Cc: Melissa Wen <melissa.srw@gmail.com>
Cc: Haneen Mohammed <hamohammed.sa@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: David Airlie <airlied@linux.ie>
Cc: dri-devel@lists.freedesktop.org
Cc: linux-kernel@vger.kernel.org
Acked-by: Melissa Wen <melissa.srw@gmail.com>
Signed-off-by: Melissa Wen <melissa.srw@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210320132840.1315853-1-dvyukov@google.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/gpu/drm/vkms/vkms_crtc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vkms/vkms_crtc.c b/drivers/gpu/drm/vkms/vkms_crtc.c
index 09c012d54d58..1ae5cd47d954 100644
--- a/drivers/gpu/drm/vkms/vkms_crtc.c
+++ b/drivers/gpu/drm/vkms/vkms_crtc.c
@@ -18,7 +18,8 @@ static enum hrtimer_restart vkms_vblank_simulate(struct hrtimer *timer)
 
 	ret_overrun = hrtimer_forward_now(&output->vblank_hrtimer,
 					  output->period_ns);
-	WARN_ON(ret_overrun != 1);
+	if (ret_overrun != 1)
+		pr_warn("%s: vblank timer overrun\n", __func__);
 
 	spin_lock(&output->lock);
 	ret = drm_crtc_handle_vblank(crtc);
-- 
2.30.2