On Sun, Mar 18, 2018 at 01:33:32PM +0000, Mark Bloch wrote:
> Currently access to hardware stats buffer isn't protected, this can
> result in multiple writes and reads at the same time to the same
> memory location. This can lead to providing an incorrect value to
> the user. Add a mutex to protect against it.
>
> Signed-off-by: Mark Bloch <markb@xxxxxxxxxxxx>
> ---
> drivers/infiniband/core/sysfs.c | 10 ++++++++--
> include/rdma/ib_verbs.h | 1 +
> 2 files changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/infiniband/core/sysfs.c b/drivers/infiniband/core/sysfs.c
> index 8ae1308e..b769d61 100644
> --- a/drivers/infiniband/core/sysfs.c
> +++ b/drivers/infiniband/core/sysfs.c
> @@ -810,10 +810,15 @@ static ssize_t show_hw_stats(struct kobject *kobj, struct attribute *attr,
> dev = port->ibdev;
> stats = port->hw_stats;
> }
> + mutex_lock(&stats->lock);
Lock is not needed here, because every thread will get its own stats.
> ret = update_hw_stats(dev, stats, hsa->port_num, hsa->index);
> if (ret)
> - return ret;
> - return print_hw_stat(stats, hsa->index, buf);
> + goto unlock;
> + ret = print_hw_stat(stats, hsa->index, buf);
> +unlock:
> + mutex_unlock(&stats->lock);
> +
> + return ret;
> }
>
> static ssize_t show_stats_lifespan(struct kobject *kobj,
> @@ -951,6 +956,7 @@ static void setup_hw_stats(struct ib_device *device, struct ib_port *port,
> sysfs_attr_init(hsag->attrs[i]);
> }
>
> + mutex_init(&stats->lock);
> /* treat an error here as non-fatal */
> hsag->attrs[i] = alloc_hsa_lifespan("lifespan", port_num);
> if (hsag->attrs[i])
> diff --git a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h
> index 73b2387..33fbccb 100644
> --- a/include/rdma/ib_verbs.h
> +++ b/include/rdma/ib_verbs.h
> @@ -484,6 +484,7 @@ enum ib_port_speed {
> * filled in by the drivers get_stats routine
> */
> struct rdma_hw_stats {
> + struct mutex lock;
> unsigned long timestamp;
> unsigned long lifespan;
> const char * const *names;
> --
> 1.8.4.3
>
> --
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