diff options
author | Arjan van de Ven <arjan@linux.intel.com> | 2010-06-17 10:02:15 (GMT) |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@suse.de> | 2010-08-10 20:47:39 (GMT) |
commit | d6e679b474c096f1125087e789e7af8886de39d3 (patch) | |
tree | b24235a50fe8c6c7d640999abd02ce6ed5d91cad /drivers | |
parent | 68c16b4117cc746a91897d629b61e5f2af18c225 (diff) | |
download | linux-fsl-qoriq-d6e679b474c096f1125087e789e7af8886de39d3.tar.xz |
serial: fix wakup races in the mrst_max3110 driver
The mrst_max3110 driver had a set of unsafe wakeup sequences
along the following line:
if (!atomic_read(&foo)) {
atomic_set(&foo, 1);
wake_up(worker_thread);
}
and the worker thread would do
if (atomic_read(&foo)) {
do_work();
atomic_set(&foo, 0);
}
which can result in various missed wakups due to test-then-set races,
as well as due to clear-after-work instead of clear-before-work.
This patch fixes these races by using the proper bit test-and-set operations,
and by doing clear-before-work.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers')
-rw-r--r-- | drivers/serial/mrst_max3110.c | 46 |
1 files changed, 18 insertions, 28 deletions
diff --git a/drivers/serial/mrst_max3110.c b/drivers/serial/mrst_max3110.c index 0341853..f6ad1ec 100644 --- a/drivers/serial/mrst_max3110.c +++ b/drivers/serial/mrst_max3110.c @@ -48,6 +48,10 @@ #define PR_FMT "mrst_max3110: " +#define UART_TX_NEEDED 1 +#define CON_TX_NEEDED 2 +#define BIT_IRQ_PENDING 3 + struct uart_max3110 { struct uart_port port; struct spi_device *spi; @@ -63,15 +67,13 @@ struct uart_max3110 { u8 clock; u8 parity, word_7bits; - atomic_t uart_tx_need; + unsigned long uart_flags; /* console related */ struct circ_buf con_xmit; - atomic_t con_tx_need; /* irq related */ u16 irq; - atomic_t irq_pending; }; /* global data structure, may need be removed */ @@ -176,10 +178,9 @@ static void serial_m3110_con_putchar(struct uart_port *port, int ch) xmit->head = (xmit->head + 1) & (PAGE_SIZE - 1); } - if (!atomic_read(&max->con_tx_need)) { - atomic_set(&max->con_tx_need, 1); + + if (!test_and_set_bit(CON_TX_NEEDED, &max->uart_flags)) wake_up_process(max->main_thread); - } } /* @@ -318,10 +319,8 @@ static void serial_m3110_start_tx(struct uart_port *port) struct uart_max3110 *max = container_of(port, struct uart_max3110, port); - if (!atomic_read(&max->uart_tx_need)) { - atomic_set(&max->uart_tx_need, 1); + if (!test_and_set_bit(UART_TX_NEEDED, &max->uart_flags)) wake_up_process(max->main_thread); - } } static void receive_chars(struct uart_max3110 *max, unsigned char *str, int len) @@ -392,32 +391,23 @@ static int max3110_main_thread(void *_max) pr_info(PR_FMT "start main thread\n"); do { - wait_event_interruptible(*wq, (atomic_read(&max->irq_pending) || - atomic_read(&max->con_tx_need) || - atomic_read(&max->uart_tx_need)) || - kthread_should_stop()); + wait_event_interruptible(*wq, max->uart_flags || kthread_should_stop()); mutex_lock(&max->thread_mutex); -#ifdef CONFIG_MRST_MAX3110_IRQ - if (atomic_read(&max->irq_pending)) { + if (test_and_clear_bit(BIT_IRQ_PENDING, &max->uart_flags)) max3110_console_receive(max); - atomic_set(&max->irq_pending, 0); - } -#endif /* first handle console output */ - if (atomic_read(&max->con_tx_need)) { + if (test_and_clear_bit(CON_TX_NEEDED, &max->uart_flags)) send_circ_buf(max, xmit); - atomic_set(&max->con_tx_need, 0); - } /* handle uart output */ - if (atomic_read(&max->uart_tx_need)) { + if (test_and_clear_bit(UART_TX_NEEDED, &max->uart_flags)) transmit_char(max); - atomic_set(&max->uart_tx_need, 0); - } + mutex_unlock(&max->thread_mutex); + } while (!kthread_should_stop()); return ret; @@ -430,10 +420,9 @@ static irqreturn_t serial_m3110_irq(int irq, void *dev_id) /* max3110's irq is a falling edge, not level triggered, * so no need to disable the irq */ - if (!atomic_read(&max->irq_pending)) { - atomic_inc(&max->irq_pending); + if (!test_and_set_bit(BIT_IRQ_PENDING, &max->uart_flags)) wake_up_process(max->main_thread); - } + return IRQ_HANDLED; } #else @@ -753,7 +742,8 @@ static int serial_m3110_probe(struct spi_device *spi) max->baud = 0; max->cur_conf = 0; - atomic_set(&max->irq_pending, 0); + max->uart_flags = 0; + /* Check if reading configuration register returns something sane */ res = RC_TAG; |