linux-kernel - [PATCH] i3c: master: dw: fix deadlock

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Message-ID: <20190125152300.248d58f4@xhacker.debian>
Date:   Fri, 25 Jan 2019 07:29:20 +0000
From:   Jisheng Zhang <Jisheng.Zhang@...aptics.com>
To:     Vitor Soares <vitor.soares@...opsys.com>,
        Boris Brezillon <bbrezillon@...nel.org>
CC:     "linux-i3c@...ts.infradead.org" <linux-i3c@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: [PATCH] i3c: master: dw: fix deadlock

In dw_i3c_master_irq_handler(), we already have gotten
&master->xferqueue.lock, if we try to get the same lock again in
dw_i3c_master_dequeue_xfer(), deadlock happens.

We fix this issue by introduing dw_i3c_master_dequeue_xfer_locked()
which does all what dw_i3c_master_dequeue_xfer() does without trying
to lock &master->xferqueue.lock.

Signed-off-by: Jisheng Zhang <Jisheng.Zhang@...aptics.com>
---
 drivers/i3c/master/dw-i3c-master.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/drivers/i3c/master/dw-i3c-master.c b/drivers/i3c/master/dw-i3c-master.c
index f8c00b94817f..bb03079fbade 100644
--- a/drivers/i3c/master/dw-i3c-master.c
+++ b/drivers/i3c/master/dw-i3c-master.c
@@ -419,12 +419,9 @@ static void dw_i3c_master_enqueue_xfer(struct dw_i3c_master *master,
 	spin_unlock_irqrestore(&master->xferqueue.lock, flags);
 }
 
-static void dw_i3c_master_dequeue_xfer(struct dw_i3c_master *master,
-				       struct dw_i3c_xfer *xfer)
+static void dw_i3c_master_dequeue_xfer_locked(struct dw_i3c_master *master,
+					      struct dw_i3c_xfer *xfer)
 {
-	unsigned long flags;
-
-	spin_lock_irqsave(&master->xferqueue.lock, flags);
 	if (master->xferqueue.cur == xfer) {
 		u32 status;
 
@@ -439,6 +436,15 @@ static void dw_i3c_master_dequeue_xfer(struct dw_i3c_master *master,
 	} else {
 		list_del_init(&xfer->node);
 	}
+}
+
+static void dw_i3c_master_dequeue_xfer(struct dw_i3c_master *master,
+				       struct dw_i3c_xfer *xfer)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&master->xferqueue.lock, flags);
+	dw_i3c_master_dequeue_xfer_locked(master, xfer);
 	spin_unlock_irqrestore(&master->xferqueue.lock, flags);
 }
 
@@ -494,7 +500,7 @@ static void dw_i3c_master_end_xfer_locked(struct dw_i3c_master *master, u32 isr)
 	complete(&xfer->comp);
 
 	if (ret < 0) {
-		dw_i3c_master_dequeue_xfer(master, xfer);
+		dw_i3c_master_dequeue_xfer_locked(master, xfer);
 		writel(readl(master->regs + DEVICE_CTRL) | DEV_CTRL_RESUME,
 		       master->regs + DEVICE_CTRL);
 	}
-- 
2.20.1