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SubjectRe: [PATCH] tty: serial: msm: Fix lock init issue with earlycon
On 10/20/2014 02:27 PM, Stephen Boyd wrote:
> On 10/17/2014 06:13 AM, Kumar Gala wrote:
>> 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
>
> [...]
>
>> 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?

Or even better: refactor __msm_console_write() so no spin_lock() is required
for the earlycon write.

FWIW, __msm_console_write() is a deadlock-waiting-to_happen since it does
not disable interrupts with spin_lock_irqsave().

Regards,
Peter Hurley


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