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serial: replace open coded mutex with a real mutex in mrst_max3110.c
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The mrst_max3110.c driver uses an open coded, non atomic variable
to create exclusion between two of its worker threads. More than that,
while the main thread does a proper set-work-clear sequence,
the other thread only does a test, with the result that no actual
exclusion is happening.

this patch replaces this open coded variable with a proper mutex

in addition, the 'lock' spinlock is removed from the per adapter structure,
the lock was only ever initialized but never used

Signed-off-by: Arjan van de Ven <[email protected]>
Signed-off-by: Alan Cox <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
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fenrus75 authored and gregkh committed Aug 10, 2010
1 parent 99dd3f6 commit 68c16b4
Showing 1 changed file with 8 additions and 7 deletions.
15 changes: 8 additions & 7 deletions drivers/serial/mrst_max3110.c
Original file line number Diff line number Diff line change
Expand Up @@ -56,8 +56,7 @@ struct uart_max3110 {
wait_queue_head_t wq;
struct task_struct *main_thread;
struct task_struct *read_thread;
int mthread_up;
spinlock_t lock;
struct mutex thread_mutex;;

u32 baud;
u16 cur_conf;
Expand Down Expand Up @@ -397,7 +396,8 @@ static int max3110_main_thread(void *_max)
atomic_read(&max->con_tx_need) ||
atomic_read(&max->uart_tx_need)) ||
kthread_should_stop());
max->mthread_up = 1;

mutex_lock(&max->thread_mutex);

#ifdef CONFIG_MRST_MAX3110_IRQ
if (atomic_read(&max->irq_pending)) {
Expand All @@ -417,7 +417,7 @@ static int max3110_main_thread(void *_max)
transmit_char(max);
atomic_set(&max->uart_tx_need, 0);
}
max->mthread_up = 0;
mutex_unlock(&max->thread_mutex);
} while (!kthread_should_stop());

return ret;
Expand All @@ -444,8 +444,9 @@ static int max3110_read_thread(void *_max)

pr_info(PR_FMT "start read thread\n");
do {
if (!max->mthread_up)
max3110_console_receive(max);
mutex_lock(&max->thread_mutex);
max3110_console_receive(max);
mutex_unlock(&max->thread_mutex);

set_current_state(TASK_INTERRUPTIBLE);
schedule_timeout(HZ / 20);
Expand Down Expand Up @@ -745,7 +746,7 @@ static int serial_m3110_probe(struct spi_device *spi)
max->name = spi->modalias; /* use spi name as the name */
max->irq = (u16)spi->irq;

spin_lock_init(&max->lock);
mutex_init(&max->thread_mutex);

max->word_7bits = 0;
max->parity = 0;
Expand Down

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