Hi Thomas, Le Wednesday 16 July 2014 à 21:04 +0000, Thomas Gleixner a écrit : > Using the wall clock time for delta time calculations is wrong to > begin with because wall clock time can be set from userspace and NTP. > Such data wants to be based on clock monotonic. > > The calcuations also are done on a nanosecond basis. Use the
Typo: calculations > nanoseconds based interface right away. > > Signed-off-by: Thomas Gleixner <[email protected]> > Cc: Jean Delvare <[email protected]> > --- > drivers/hwmon/ibmaem.c | 6 ++---- > 1 file changed, 2 insertions(+), 4 deletions(-) > > Index: tip/drivers/hwmon/ibmaem.c > =================================================================== > --- tip.orig/drivers/hwmon/ibmaem.c > +++ tip/drivers/hwmon/ibmaem.c > @@ -842,11 +842,10 @@ static ssize_t aem_show_power(struct dev > struct aem_data *data = dev_get_drvdata(dev); > u64 before, after, delta, time; > signed long leftover; > - struct timespec b, a; > > mutex_lock(&data->lock); > update_aem_energy_one(data, attr->index); > - getnstimeofday(&b); > + time = ktime_get_ns(); > before = data->energy[attr->index]; > > leftover = schedule_timeout_interruptible( > @@ -858,11 +857,10 @@ static ssize_t aem_show_power(struct dev > } > > update_aem_energy_one(data, attr->index); > - getnstimeofday(&a); > + time = ktime_get_ns() - time; > after = data->energy[attr->index]; > mutex_unlock(&data->lock); > > - time = timespec_to_ns(&a) - timespec_to_ns(&b); > delta = (after - before) * UJ_PER_MJ; > > return sprintf(buf, "%llu\n", I'm not familiar with the driver and I can't test it, and I'm not familiar with kernel timekeeping either. All I can say is that the changes look reasonable and good. Acked-by: Jean Delvare <[email protected]> Darrick, maybe you want to comment or test? -- Jean Delvare SUSE L3 Support -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
