| Message ID | 20210911113645.2547272-1-drhunter95@gmail.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | workaround regression in ina2xx introduced by cb47755725da("time: Prevent undefined behaviour in timespec64_to_ns()") | expand |
On Sat, 11 Sep 2021 12:36:23 +0100 Iain Hunter <drhunter95@gmail.com> wrote: > From: Iain Hunter <iain@hunterembedded.co.uk> > > That change adds an error check to avoid saturation during multiplication > to calculate nano seconds in timespec64_to_ns(). > In ina2xx_capture_thread() a timespec64 structure is used to calculate > the delta time until the next sample time. This delta can be negative if > the next sample time was in the past. In the -1 case timespec64_to_ns() > now clamps the -1 second value to KTIME_MAX. This essentially puts ina2xx > thread to sleep forever. > Proposed patch is to replace the call to timespec64_to_ns() with the > contents of that function without the overflow test introduced by the > commit (ie revert to pre kernel 5.4 behaviour) > > Signed-off-by: Iain Hunter <iain@hunterembedded.co.uk> Needs a fixes tag with the patch you mention above that added the check so that we can tell how far back this needs to be backported. > --- > drivers/iio/adc/ina2xx-adc.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/iio/adc/ina2xx-adc.c b/drivers/iio/adc/ina2xx-adc.c > index a4b2ff9e0..ba3e98fde 100644 > --- a/drivers/iio/adc/ina2xx-adc.c > +++ b/drivers/iio/adc/ina2xx-adc.c > @@ -777,6 +777,7 @@ static int ina2xx_capture_thread(void *data) > int ret; > struct timespec64 next, now, delta; > s64 delay_us; > + s64 delta_ns; > > /* > * Poll a bit faster than the chip internal Fs, in case > @@ -818,7 +819,8 @@ static int ina2xx_capture_thread(void *data) > do { > timespec64_add_ns(&next, 1000 * sampling_us); > delta = timespec64_sub(next, now); > - delay_us = div_s64(timespec64_to_ns(&delta), 1000); > + delta_ns = (((s64)delta.tv_sec) * NSEC_PER_SEC)+delta.tv_nsec; spaces around the + > + delay_us = div_s64(delta_ns, 1000); Hmm. The negative timestamp is a bit of a mess anyway. Perhaps we can do something neater using the standard functions by checking the validity of the timestamp using timespec64_valid_strict() in the while loop and dropping the div_s64 out of the loop. What do you think? Would need a comment to explain why we the check on it being valid though. Jonathan > } while (delay_us <= 0); > > usleep_range(delay_us, (delay_us * 3) >> 1);
diff --git a/drivers/iio/adc/ina2xx-adc.c b/drivers/iio/adc/ina2xx-adc.c index a4b2ff9e0..ba3e98fde 100644 --- a/drivers/iio/adc/ina2xx-adc.c +++ b/drivers/iio/adc/ina2xx-adc.c @@ -777,6 +777,7 @@ static int ina2xx_capture_thread(void *data) int ret; struct timespec64 next, now, delta; s64 delay_us; + s64 delta_ns; /* * Poll a bit faster than the chip internal Fs, in case @@ -818,7 +819,8 @@ static int ina2xx_capture_thread(void *data) do { timespec64_add_ns(&next, 1000 * sampling_us); delta = timespec64_sub(next, now); - delay_us = div_s64(timespec64_to_ns(&delta), 1000); + delta_ns = (((s64)delta.tv_sec) * NSEC_PER_SEC)+delta.tv_nsec; + delay_us = div_s64(delta_ns, 1000); } while (delay_us <= 0); usleep_range(delay_us, (delay_us * 3) >> 1);