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Message-Id: <20220417125519.82618-1-duoming@zju.edu.cn> Date: Sun, 17 Apr 2022 20:55:19 +0800 From: Duoming Zhou <duoming@....edu.cn> To: linux-kernel@...r.kernel.org, jes@...ined-monkey.org Cc: netdev@...r.kernel.org, linux-hippi@...site.dk, pabeni@...hat.com, kuba@...nel.org, davem@...emloft.net, Duoming Zhou <duoming@....edu.cn> Subject: [PATCH] drivers: net: hippi: Fix deadlock in rr_close() There is a deadlock in rr_close(), which is shown below: (Thread 1) | (Thread 2) | rr_open() rr_close() | add_timer() spin_lock_irqsave() //(1) | (wait a time) ... | rr_timer() del_timer_sync() | spin_lock_irqsave() //(2) (wait timer to stop) | ... We hold rrpriv->lock in position (1) of thread 1 and use del_timer_sync() to wait timer to stop, but timer handler also need rrpriv->lock in position (2) of thread 2. As a result, rr_close() will block forever. This patch extracts del_timer_sync() from the protection of spin_lock_irqsave(), which could let timer handler to obtain the needed lock. Signed-off-by: Duoming Zhou <duoming@....edu.cn> --- drivers/net/hippi/rrunner.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/net/hippi/rrunner.c b/drivers/net/hippi/rrunner.c index 16105292b14..74e845fa2e0 100644 --- a/drivers/net/hippi/rrunner.c +++ b/drivers/net/hippi/rrunner.c @@ -1355,7 +1355,9 @@ static int rr_close(struct net_device *dev) rrpriv->fw_running = 0; + spin_unlock_irqrestore(&rrpriv->lock, flags); del_timer_sync(&rrpriv->timer); + spin_lock_irqsave(&rrpriv->lock, flags); writel(0, ®s->TxPi); writel(0, ®s->IpRxPi); -- 2.17.1
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