Discussion:
[PATCH] tty: serial: msm: Fix lock init issue with earlycon
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Kumar Gala
2014-10-17 13:13:08 UTC
Permalink
With CONFIG_DEBUG_SPINLOCK enabled we see:

BUG: spinlock bad magic on CPU#0, swapper/0
lock: early_console_dev+0x8/0x160, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0
CPU: 0 PID: 0 Comm: swapper Not tainted 3.17.0-09733-gb446b33-dirty #18
Call trace:
[<c0087ba0>] dump_backtrace+0x0/0x140
[<c0087cf0>] show_stack+0x10/0x1c
[<c0598be0>] dump_stack+0x74/0xb8
[<c00cb720>] spin_dump+0x78/0x88
[<c00cb754>] spin_bug+0x24/0x34
[<c00cb7e4>] do_raw_spin_lock+0x30/0x158
[<c059ea2c>] _raw_spin_lock+0x1c/0x2c
[<c02e0e30>] __msm_console_write+0x68/0x154
[<c02e0f50>] msm_serial_early_write_dm+0x14/0x20
[<c00cf040>] call_console_drivers.constprop.23+0xa4/0xc4
[<c00d00c4>] console_unlock+0x2a8/0x330
[<c00d121c>] register_console+0x26c/0x338
[<c0805af4>] setup_earlycon+0x2c0/0x300
[<c0805c48>] msm_serial_dm_setup_earlycon+0x18/0x24
[<c07ed158>] do_early_param+0x84/0xd0
[<c00aec18>] parse_args+0x2b4/0x3ec
[<c07ed588>] parse_early_options+0x2c/0x38
[<c07ed5c8>] parse_early_param+0x34/0x50
[<c07f03c0>] setup_arch+0x290/0x604
[<c07ed67c>] start_kernel+0x94/0x38c

As the earlycon write function for msm requires a lock, we need to init
it as part of the setup call.

Signed-off-by: Kumar Gala <***@codeaurora.org>
---
drivers/tty/serial/msm_serial.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c
index 4b6c783..8ab27c9 100644
--- a/drivers/tty/serial/msm_serial.c
+++ b/drivers/tty/serial/msm_serial.c
@@ -973,6 +973,8 @@ msm_serial_early_console_setup(struct earlycon_device *device, const char *opt)
if (!device->port.membase)
return -ENODEV;

+ spin_lock_init(&device->port.lock);
+
device->con->write = msm_serial_early_write;
return 0;
}
@@ -995,6 +997,8 @@ msm_serial_early_console_setup_dm(struct earlycon_device *device,
if (!device->port.membase)
return -ENODEV;

+ spin_lock_init(&device->port.lock);
+
device->con->write = msm_serial_early_write_dm;
return 0;
}
--
Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project
Stephen Boyd
2014-10-20 18:27:02 UTC
Permalink
Post by Kumar Gala
BUG: spinlock bad magic on CPU#0, swapper/0
lock: early_console_dev+0x8/0x160, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0
CPU: 0 PID: 0 Comm: swapper Not tainted 3.17.0-09733-gb446b33-dirty #18
[...]
Post by Kumar Gala
diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c
index 4b6c783..8ab27c9 100644
--- a/drivers/tty/serial/msm_serial.c
+++ b/drivers/tty/serial/msm_serial.c
@@ -973,6 +973,8 @@ msm_serial_early_console_setup(struct earlycon_device *device, const char *opt)
if (!device->port.membase)
return -ENODEV;
+ spin_lock_init(&device->port.lock);
+
device->con->write = msm_serial_early_write;
return 0;
}
@@ -995,6 +997,8 @@ msm_serial_early_console_setup_dm(struct earlycon_device *device,
if (!device->port.membase)
return -ENODEV;
+ spin_lock_init(&device->port.lock);
+
device->con->write = msm_serial_early_write_dm;
return 0;
}
Could this be done in the tty core instead?
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project
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