Re: [RFC PATCH 04/11] drivers/base/devcoredump: convert devcd_count to counter_atomic

Greg KH
2020-09-23T10:31:32Z

On Tue, Sep 22, 2020 at 07:43:33PM -0600, Shuah Khan wrote:
> counter_atomic is introduced to be used when a variable is used as
> a simple counter and doesn't guard object lifetimes. This clearly
> differentiates atomic_t usages that guard object lifetimes.
>
> counter_atomic variables will wrap around to 0 when it overflows and
> should not be used to guard resource lifetimes, device usage and
> open counts that control state changes, and pm states.
>
> devcd_count is used to track dev_coredumpm device count and used in
> device name string. It doesn't guard object lifetimes, device usage
> counts, device open counts, and pm states. There is very little chance
> of this counter overflowing. Convert it to use counter_atomic.
>
> This conversion doesn't change the oveflow wrap around behavior.
>
> Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
> ---
> drivers/base/devcoredump.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/base/devcoredump.c b/drivers/base/devcoredump.c
> index e42d0b514384..d719424d1e0b 100644
> --- a/drivers/base/devcoredump.c
> +++ b/drivers/base/devcoredump.c
> @@ -16,6 +16,7 @@
> #include <linux/slab.h>
> #include <linux/fs.h>
> #include <linux/workqueue.h>
> +#include <linux/counters.h>
>
> static struct class devcd_class;
>
> @@ -255,7 +256,7 @@ void dev_coredumpm(struct device *dev, struct module *owner,
> void *data, size_t datalen),
> void (*free)(void *data))
> {
> - static atomic_t devcd_count = ATOMIC_INIT(0);
> + static struct counter_atomic devcd_count = COUNTER_ATOMIC_INIT(0);
> struct devcd_entry *devcd;
> struct device *existing;
>
> @@ -286,7 +287,7 @@ void dev_coredumpm(struct device *dev, struct module *owner,
> device_initialize(&devcd->devcd_dev);
>
> dev_set_name(&devcd->devcd_dev, "devcd%d",
> - atomic_inc_return(&devcd_count));
> + counter_atomic_inc_return(&devcd_count));
> devcd->devcd_dev.class = &devcd_class;
>
> if (device_add(&devcd->devcd_dev))
> --
> 2.25.1
>

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>