linux-kernel - [PATCH] media: v4l2-mem2mem: add lock to protect parameter num

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Message-ID: <20230417081740.26075-1-yunfei.dong@mediatek.com>
Date:   Mon, 17 Apr 2023 16:17:40 +0800
From:   Yunfei Dong <yunfei.dong@...iatek.com>
To:     Hans Verkuil <hverkuil-cisco@...all.nl>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
CC:     Pina Chen <pina.chen@...iatek.com>,
        Yunfei Dong <yunfei.dong@...iatek.com>,
        <linux-media@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>
Subject: [PATCH] media: v4l2-mem2mem: add lock to protect parameter num_rdy

Getting below error when using KCSAN to check the driver. Adding lock to
protect parameter num_rdy when getting the value with function:
v4l2_m2m_num_src_bufs_ready/v4l2_m2m_num_dst_bufs_ready.

kworker/u16:3: [name:report&]BUG: KCSAN: data-race in v4l2_m2m_buf_queue
kworker/u16:3: [name:report&]

kworker/u16:3: [name:report&]read-write to 0xffffff8105f35b94 of 1 bytes by task 20865 on cpu 7:
kworker/u16:3:  v4l2_m2m_buf_queue+0xd8/0x10c

Signed-off-by: Pina Chen <pina.chen@...iatek.com>
Signed-off-by: Yunfei Dong <yunfei.dong@...iatek.com>
---
 include/media/v4l2-mem2mem.h | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/include/media/v4l2-mem2mem.h b/include/media/v4l2-mem2mem.h
index bb9de6a899e0..d6c8eb2b5201 100644
--- a/include/media/v4l2-mem2mem.h
+++ b/include/media/v4l2-mem2mem.h
@@ -593,7 +593,14 @@ void v4l2_m2m_buf_queue(struct v4l2_m2m_ctx *m2m_ctx,
 static inline
 unsigned int v4l2_m2m_num_src_bufs_ready(struct v4l2_m2m_ctx *m2m_ctx)
 {
-	return m2m_ctx->out_q_ctx.num_rdy;
+	unsigned int num_buf_rdy;
+	unsigned long flags;
+
+	spin_lock_irqsave(&m2m_ctx->out_q_ctx.rdy_spinlock, flags);
+	num_buf_rdy = m2m_ctx->out_q_ctx.num_rdy;
+	spin_unlock_irqrestore(&m2m_ctx->out_q_ctx.rdy_spinlock, flags);
+
+	return num_buf_rdy;
 }
 
 /**
@@ -605,7 +612,14 @@ unsigned int v4l2_m2m_num_src_bufs_ready(struct v4l2_m2m_ctx *m2m_ctx)
 static inline
 unsigned int v4l2_m2m_num_dst_bufs_ready(struct v4l2_m2m_ctx *m2m_ctx)
 {
-	return m2m_ctx->cap_q_ctx.num_rdy;
+	unsigned int num_buf_rdy;
+	unsigned long flags;
+
+	spin_lock_irqsave(&m2m_ctx->cap_q_ctx.rdy_spinlock, flags);
+	num_buf_rdy = m2m_ctx->cap_q_ctx.num_rdy;
+	spin_unlock_irqrestore(&m2m_ctx->cap_q_ctx.rdy_spinlock, flags);
+
+	return num_buf_rdy;
 }
 
 /**
-- 
2.18.0