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reentrancy without mutexe #94

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48 changes: 17 additions & 31 deletions drivers/spi/spi.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1633,8 +1633,6 @@ EXPORT_SYMBOL_GPL(spi_bus_unlock);
/* portable code must never pass more than 32 bytes */
#define SPI_BUFSIZ max(32,SMP_CACHE_BYTES)

static u8 *buf;

/**
* spi_write_then_read - SPI synchronous write followed by read
* @spi: device with which data will be exchanged
Expand All @@ -1658,7 +1656,7 @@ int spi_write_then_read(struct spi_device *spi,
const void *txbuf, unsigned n_tx,
void *rxbuf, unsigned n_rx)
{
static DEFINE_MUTEX(lock);
u8 buf[SPI_BUFSIZ];

int status;
struct spi_message message;
Expand All @@ -1670,38 +1668,35 @@ int spi_write_then_read(struct spi_device *spi,
* keep heap costs out of the hot path unless someone else is
* using the pre-allocated buffer or the transfer is too large.
*/
if ((n_tx + n_rx) > SPI_BUFSIZ || !mutex_trylock(&lock)) {
local_buf = kmalloc(max((unsigned)SPI_BUFSIZ, n_tx + n_rx),
GFP_KERNEL | GFP_DMA);
if ((n_tx + n_rx) > SPI_BUFSIZ) {
local_buf = kmalloc(n_tx + n_rx, GFP_KERNEL | GFP_DMA);
if (!local_buf)
return -ENOMEM;
} else {
local_buf = buf;
}

spi_message_init(&message);
memset(x, 0, sizeof x);
if (n_tx) {
x[0].len = n_tx;
if (n_tx && txbuf) {
x[0].len = n_tx;
x[0].tx_buf = local_buf;
x[0].rx_buf = NULL;
spi_message_add_tail(&x[0], &message);
memcpy(local_buf, txbuf, n_tx);
}
if (n_rx) {
x[1].len = n_rx;
if (n_rx && rxbuf) {
x[1].len = n_rx;
x[1].rx_buf = local_buf + n_tx;
x[1].tx_buf = NULL;
spi_message_add_tail(&x[1], &message);
}

memcpy(local_buf, txbuf, n_tx);
x[0].tx_buf = local_buf;
x[1].rx_buf = local_buf + n_tx;

/* do the i/o */
status = spi_sync(spi, &message);
if (status == 0)
if (x[1].rx_buf && (status == 0))
memcpy(rxbuf, x[1].rx_buf, n_rx);

if (x[0].tx_buf == buf)
mutex_unlock(&lock);
else
if (local_buf != buf)
kfree(local_buf);

return status;
Expand All @@ -1714,26 +1709,17 @@ static int __init spi_init(void)
{
int status;

buf = kmalloc(SPI_BUFSIZ, GFP_KERNEL);
if (!buf) {
status = -ENOMEM;
goto err0;
}

status = bus_register(&spi_bus_type);
if (status < 0)
goto err1;
goto err0;

status = class_register(&spi_master_class);
if (status < 0)
goto err2;
goto err1;
return 0;

err2:
bus_unregister(&spi_bus_type);
err1:
kfree(buf);
buf = NULL;
bus_unregister(&spi_bus_type);
err0:
return status;
}
Expand Down