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SubjectRe: [RFC PATCH 1/5] fsi/scom: Add mutex around FSI2PIB accesses
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On 06/12/2018 12:19 AM, Benjamin Herrenschmidt wrote:
> Otherwise, multiple clients can open the driver and attempt
> to access the PIB at the same time, thus clobbering each other
> in the process.
>
> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

Reviewed-by: Eddie James <eajames@linux.vnet.ibm.com>

> ---
> drivers/fsi/fsi-scom.c | 25 ++++++++++++++++++-------
> 1 file changed, 18 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/fsi/fsi-scom.c b/drivers/fsi/fsi-scom.c
> index c8eb5e5b94a7..3cba0eb645e1 100644
> --- a/drivers/fsi/fsi-scom.c
> +++ b/drivers/fsi/fsi-scom.c
> @@ -37,6 +37,7 @@ struct scom_device {
> struct list_head link;
> struct fsi_device *fsi_dev;
> struct miscdevice mdev;
> + struct mutex lock;
> char name[32];
> int idx;
> };
> @@ -53,21 +54,26 @@ static int put_scom(struct scom_device *scom_dev, uint64_t value,
> int rc;
> uint32_t data;
>
> + mutex_lock(&scom_dev->lock);
> +
> data = cpu_to_be32((value >> 32) & 0xffffffff);
> rc = fsi_device_write(scom_dev->fsi_dev, SCOM_DATA0_REG, &data,
> sizeof(uint32_t));
> if (rc)
> - return rc;
> + goto bail;
>
> data = cpu_to_be32(value & 0xffffffff);
> rc = fsi_device_write(scom_dev->fsi_dev, SCOM_DATA1_REG, &data,
> sizeof(uint32_t));
> if (rc)
> - return rc;
> + goto bail;
>
> data = cpu_to_be32(SCOM_WRITE_CMD | addr);
> - return fsi_device_write(scom_dev->fsi_dev, SCOM_CMD_REG, &data,
> + rc = fsi_device_write(scom_dev->fsi_dev, SCOM_CMD_REG, &data,
> sizeof(uint32_t));
> + bail:
> + mutex_unlock(&scom_dev->lock);
> + return rc;
> }
>
> static int get_scom(struct scom_device *scom_dev, uint64_t *value,
> @@ -76,27 +82,31 @@ static int get_scom(struct scom_device *scom_dev, uint64_t *value,
> uint32_t result, data;
> int rc;
>
> +
> + mutex_lock(&scom_dev->lock);
> *value = 0ULL;
> data = cpu_to_be32(addr);
> rc = fsi_device_write(scom_dev->fsi_dev, SCOM_CMD_REG, &data,
> sizeof(uint32_t));
> if (rc)
> - return rc;
> + goto bail;
>
> rc = fsi_device_read(scom_dev->fsi_dev, SCOM_DATA0_REG, &result,
> sizeof(uint32_t));
> if (rc)
> - return rc;
> + goto bail;
>
> *value |= (uint64_t)cpu_to_be32(result) << 32;
> rc = fsi_device_read(scom_dev->fsi_dev, SCOM_DATA1_REG, &result,
> sizeof(uint32_t));
> if (rc)
> - return rc;
> + goto bail;
>
> *value |= cpu_to_be32(result);
>
> - return 0;
> + bail:
> + mutex_unlock(&scom_dev->lock);
> + return rc;
> }
>
> static ssize_t scom_read(struct file *filep, char __user *buf, size_t len,
> @@ -183,6 +193,7 @@ static int scom_probe(struct device *dev)
> if (!scom)
> return -ENOMEM;
>
> + mutex_init(&scom->lock);
> scom->idx = ida_simple_get(&scom_ida, 1, INT_MAX, GFP_KERNEL);
> snprintf(scom->name, sizeof(scom->name), "scom%d", scom->idx);
> scom->fsi_dev = fsi_dev;

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