2021-04-29 15:17:41

by Eddie James

Subject: [PATCH] hwmon: (occ) Fix poll rate limiting

The poll rate limiter time was initialized at zero. This breaks the
comparison in time_after if jiffies is large. Switch to storing the
next update time rather than the previous time, and initialize the
time when the device is probed.

Fixes: c10e753d43eb ("hwmon (occ): Add sensor types and versions")
Signed-off-by: Eddie James <[email protected]>
---
drivers/hwmon/occ/common.c | 5 +++--
drivers/hwmon/occ/common.h | 2 +-
2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/occ/common.c b/drivers/hwmon/occ/common.c
index f1ac153d0b56..967532afb1c0 100644
--- a/drivers/hwmon/occ/common.c
+++ b/drivers/hwmon/occ/common.c
@@ -217,9 +217,9 @@ int occ_update_response(struct occ *occ)
return rc;

/* limit the maximum rate of polling the OCC */
- if (time_after(jiffies, occ->last_update + OCC_UPDATE_FREQUENCY)) {
+ if (time_after(jiffies, occ->next_update)) {
rc = occ_poll(occ);
- occ->last_update = jiffies;
+ occ->next_update = jiffies + OCC_UPDATE_FREQUENCY;
} else {
rc = occ->last_error;
}
@@ -1165,6 +1165,7 @@ int occ_setup(struct occ *occ, const char *name)
return rc;
}

+ occ->next_update = jiffies + OCC_UPDATE_FREQUENCY;
occ_parse_poll_response(occ);

rc = occ_setup_sensor_attrs(occ);
diff --git a/drivers/hwmon/occ/common.h b/drivers/hwmon/occ/common.h
index 67e6968b8978..e6df719770e8 100644
--- a/drivers/hwmon/occ/common.h
+++ b/drivers/hwmon/occ/common.h
@@ -99,7 +99,7 @@ struct occ {
u8 poll_cmd_data; /* to perform OCC poll command */
int (*send_cmd)(struct occ *occ, u8 *cmd);

- unsigned long last_update;
+ unsigned long next_update;
struct mutex lock; /* lock OCC access */

struct device *hwmon;
--
2.27.0

2021-04-30 01:30:13

by Guenter Roeck

Subject: Re: [PATCH] hwmon: (occ) Fix poll rate limiting

On Thu, Apr 29, 2021 at 10:13:36AM -0500, Eddie James wrote:
> The poll rate limiter time was initialized at zero. This breaks the
> comparison in time_after if jiffies is large. Switch to storing the
> next update time rather than the previous time, and initialize the
> time when the device is probed.
>
> Fixes: c10e753d43eb ("hwmon (occ): Add sensor types and versions")
> Signed-off-by: Eddie James <[email protected]>

Applied.

Thanks,
Guenter

> ---
> drivers/hwmon/occ/common.c | 5 +++--
> drivers/hwmon/occ/common.h | 2 +-
> 2 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/hwmon/occ/common.c b/drivers/hwmon/occ/common.c
> index f1ac153d0b56..967532afb1c0 100644
> --- a/drivers/hwmon/occ/common.c
> +++ b/drivers/hwmon/occ/common.c
> @@ -217,9 +217,9 @@ int occ_update_response(struct occ *occ)
> return rc;
>
> /* limit the maximum rate of polling the OCC */
> - if (time_after(jiffies, occ->last_update + OCC_UPDATE_FREQUENCY)) {
> + if (time_after(jiffies, occ->next_update)) {
> rc = occ_poll(occ);
> - occ->last_update = jiffies;
> + occ->next_update = jiffies + OCC_UPDATE_FREQUENCY;
> } else {
> rc = occ->last_error;
> }
> @@ -1165,6 +1165,7 @@ int occ_setup(struct occ *occ, const char *name)
> return rc;
> }
>
> + occ->next_update = jiffies + OCC_UPDATE_FREQUENCY;
> occ_parse_poll_response(occ);
>
> rc = occ_setup_sensor_attrs(occ);
> diff --git a/drivers/hwmon/occ/common.h b/drivers/hwmon/occ/common.h
> index 67e6968b8978..e6df719770e8 100644
> --- a/drivers/hwmon/occ/common.h
> +++ b/drivers/hwmon/occ/common.h
> @@ -99,7 +99,7 @@ struct occ {
> u8 poll_cmd_data; /* to perform OCC poll command */
> int (*send_cmd)(struct occ *occ, u8 *cmd);
>
> - unsigned long last_update;
> + unsigned long next_update;
> struct mutex lock; /* lock OCC access */
>
> struct device *hwmon;