linux-kernel - [PATCH AUTOSEL 4.4 29/60] serial: amba-pl011: Make sure we initialize the port.lock spinlock

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Date:   Wed, 17 Jun 2020 21:29:33 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     John Stultz <john.stultz@...aro.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Jiri Slaby <jslaby@...e.com>, linux-serial@...r.kernel.org,
        Valentin Schneider <valentin.schneider@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 4.4 29/60] serial: amba-pl011: Make sure we initialize the port.lock spinlock

From: John Stultz <john.stultz@...aro.org>

[ Upstream commit 8508f4cba308f785b2fd4b8c38849c117b407297 ]

Valentine reported seeing:

[    3.626638] INFO: trying to register non-static key.
[    3.626639] the code is fine but needs lockdep annotation.
[    3.626640] turning off the locking correctness validator.
[    3.626644] CPU: 7 PID: 51 Comm: kworker/7:1 Not tainted 5.7.0-rc2-00115-g8c2e9790f196 #116
[    3.626646] Hardware name: HiKey960 (DT)
[    3.626656] Workqueue: events deferred_probe_work_func
[    3.632476] sd 0:0:0:0: [sda] Optimal transfer size 8192 bytes not a multiple of physical block size (16384 bytes)
[    3.640220] Call trace:
[    3.640225]  dump_backtrace+0x0/0x1b8
[    3.640227]  show_stack+0x20/0x30
[    3.640230]  dump_stack+0xec/0x158
[    3.640234]  register_lock_class+0x598/0x5c0
[    3.640235]  __lock_acquire+0x80/0x16c0
[    3.640236]  lock_acquire+0xf4/0x4a0
[    3.640241]  _raw_spin_lock_irqsave+0x70/0xa8
[    3.640245]  uart_add_one_port+0x388/0x4b8
[    3.640248]  pl011_register_port+0x70/0xf0
[    3.640250]  pl011_probe+0x184/0x1b8
[    3.640254]  amba_probe+0xdc/0x180
[    3.640256]  really_probe+0xe0/0x338
[    3.640257]  driver_probe_device+0x60/0xf8
[    3.640259]  __device_attach_driver+0x8c/0xd0
[    3.640260]  bus_for_each_drv+0x84/0xd8
[    3.640261]  __device_attach+0xe4/0x140
[    3.640263]  device_initial_probe+0x1c/0x28
[    3.640265]  bus_probe_device+0xa4/0xb0
[    3.640266]  deferred_probe_work_func+0x7c/0xb8
[    3.640269]  process_one_work+0x2c0/0x768
[    3.640271]  worker_thread+0x4c/0x498
[    3.640272]  kthread+0x14c/0x158
[    3.640275]  ret_from_fork+0x10/0x1c

Which seems to be due to the fact that after allocating the uap
structure, nothing initializes the spinlock.

Its a little confusing, as uart_port_spin_lock_init() is one
place where the lock is supposed to be initialized, but it has
an exception for the case where the port is a console.

This makes it seem like a deeper fix is needed to properly
register the console, but I'm not sure what that entails, and
Andy suggested that this approach is less invasive.

Thus, this patch resolves the issue by initializing the spinlock
in the driver, and resolves the resulting warning.

Cc: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Russell King <linux@...linux.org.uk>
Cc: Jiri Slaby <jslaby@...e.com>
Cc: linux-serial@...r.kernel.org
Reported-by: Valentin Schneider <valentin.schneider@....com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>
Signed-off-by: John Stultz <john.stultz@...aro.org>
Reviewed-and-tested-by: Valentin Schneider <valentin.schneider@....com>
Link: https://lore.kernel.org/r/20200428184050.6501-1-john.stultz@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/tty/serial/amba-pl011.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 899a77187bde..c5da46f7b909 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -2323,6 +2323,7 @@ static int pl011_setup_port(struct device *dev, struct uart_amba_port *uap,
 	uap->port.fifosize = uap->fifosize;
 	uap->port.flags = UPF_BOOT_AUTOCONF;
 	uap->port.line = index;
+	spin_lock_init(&uap->port.lock);
 
 	amba_ports[index] = uap;
 
-- 
2.25.1