Hi Nicholas,
On Sun, May 14, 2017 at 10:43 AM, Nicholas Mc Guire <[email protected]> wrote:
> If the timeout-case prints a warning message then probably the interrupted
> case should also. Further, wait_for_completion_interruptible_timeout()
> returns long not int.
>
> Fixes: commit 03b262f2bbf4 ("iio:pressure: initial zpa2326 barometer support")
> Signed-off-by: Nicholas Mc Guire <[email protected]>
> ---
>
> The original control-flow was technically not wrong just confusing and a bit
> complicated. Not clear if reporting the interrupted case actually is useful,
> but given that the timeout is relatively long (200ms) it is not that unlikely
> so differentiating the cases seems helpful.
>
> Patch was compile-tested with: x86_64_defconfig + CONFIG_IIO=m, CONFIG_ZPA2326=m
>
> Patch is against v4.11 (localversion-next is next-20170512)
>
> drivers/iio/pressure/zpa2326.c | 17 ++++++++++-------
> 1 file changed, 10 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/iio/pressure/zpa2326.c b/drivers/iio/pressure/zpa2326.c
> index e58a0ad..617926f 100644
> --- a/drivers/iio/pressure/zpa2326.c
> +++ b/drivers/iio/pressure/zpa2326.c
> @@ -867,12 +867,13 @@ static int zpa2326_wait_oneshot_completion(const struct iio_dev *indio_dev,
> {
> int ret;
> unsigned int val;
> + long timeout;
>
> zpa2326_dbg(indio_dev, "waiting for one shot completion interrupt");
>
> - ret = wait_for_completion_interruptible_timeout(
> + timeout = wait_for_completion_interruptible_timeout(
> &private->data_ready, ZPA2326_CONVERSION_JIFFIES);
> - if (ret > 0)
> + if (timeout > 0)
Check for strict positive timeout.
> /*
> * Interrupt handler completed before timeout: return operation
> * status.
> @@ -882,13 +883,15 @@ static int zpa2326_wait_oneshot_completion(const struct iio_dev *indio_dev,
> /* Clear all interrupts just to be sure. */
> regmap_read(private->regmap, ZPA2326_INT_SOURCE_REG, &val);
>
> - if (!ret)
> + if (!timeout) {
Check for zero timeout.
> /* Timed out. */
> + zpa2326_warn(indio_dev, "no one shot interrupt occurred (%ld)",
> + timeout);
> ret = -ETIME;
> -
> - if (ret != -ERESTARTSYS)
> - zpa2326_warn(indio_dev, "no one shot interrupt occurred (%d)",
> - ret);
> + } else if (timeout < 0) {
So if we get here, timeout is always strict negative, so the check can
be removed.
> + zpa2326_warn(indio_dev, "wait for one shot interrupt canceled");
> + ret = -ERESTARTSYS;
> + }
>
> return ret;
But gcc-4.1.2 is not smart enough:
drivers/iio/pressure/zpa2326.c:868: warning: ‘ret’ may be used
uninitialized in this function
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
On Tue, 4 Jul 2017 12:40:33 +0200
Geert Uytterhoeven <[email protected]> wrote:
> Hi Nicholas,
>
> On Sun, May 14, 2017 at 10:43 AM, Nicholas Mc Guire <[email protected]> wrote:
> > If the timeout-case prints a warning message then probably the interrupted
> > case should also. Further, wait_for_completion_interruptible_timeout()
> > returns long not int.
> >
> > Fixes: commit 03b262f2bbf4 ("iio:pressure: initial zpa2326 barometer support")
> > Signed-off-by: Nicholas Mc Guire <[email protected]>
> > ---
> >
> > The original control-flow was technically not wrong just confusing and a bit
> > complicated. Not clear if reporting the interrupted case actually is useful,
> > but given that the timeout is relatively long (200ms) it is not that unlikely
> > so differentiating the cases seems helpful.
> >
> > Patch was compile-tested with: x86_64_defconfig + CONFIG_IIO=m, CONFIG_ZPA2326=m
> >
> > Patch is against v4.11 (localversion-next is next-20170512)
> >
> > drivers/iio/pressure/zpa2326.c | 17 ++++++++++-------
> > 1 file changed, 10 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/iio/pressure/zpa2326.c b/drivers/iio/pressure/zpa2326.c
> > index e58a0ad..617926f 100644
> > --- a/drivers/iio/pressure/zpa2326.c
> > +++ b/drivers/iio/pressure/zpa2326.c
> > @@ -867,12 +867,13 @@ static int zpa2326_wait_oneshot_completion(const struct iio_dev *indio_dev,
> > {
> > int ret;
> > unsigned int val;
> > + long timeout;
> >
> > zpa2326_dbg(indio_dev, "waiting for one shot completion interrupt");
> >
> > - ret = wait_for_completion_interruptible_timeout(
> > + timeout = wait_for_completion_interruptible_timeout(
> > &private->data_ready, ZPA2326_CONVERSION_JIFFIES);
> > - if (ret > 0)
> > + if (timeout > 0)
>
> Check for strict positive timeout.
>
> > /*
> > * Interrupt handler completed before timeout: return operation
> > * status.
> > @@ -882,13 +883,15 @@ static int zpa2326_wait_oneshot_completion(const struct iio_dev *indio_dev,
> > /* Clear all interrupts just to be sure. */
> > regmap_read(private->regmap, ZPA2326_INT_SOURCE_REG, &val);
> >
> > - if (!ret)
> > + if (!timeout) {
>
> Check for zero timeout.
>
> > /* Timed out. */
> > + zpa2326_warn(indio_dev, "no one shot interrupt occurred (%ld)",
> > + timeout);
> > ret = -ETIME;
> > -
> > - if (ret != -ERESTARTSYS)
> > - zpa2326_warn(indio_dev, "no one shot interrupt occurred (%d)",
> > - ret);
> > + } else if (timeout < 0) {
>
> So if we get here, timeout is always strict negative, so the check can
> be removed.
>
> > + zpa2326_warn(indio_dev, "wait for one shot interrupt canceled");
> > + ret = -ERESTARTSYS;
> > + }
> >
> > return ret;
>
> But gcc-4.1.2 is not smart enough:
>
> drivers/iio/pressure/zpa2326.c:868: warning: ‘ret’ may be used
> uninitialized in this function
Good analysis. Care to send the obvious patch?
J
>
> Gr{oetje,eeting}s,
>
> Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
> -- Linus Torvalds
> --
> To unsubscribe from this list: send the line "unsubscribe linux-iio" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Jul 04, 2017 at 08:08:53PM +0100, Jonathan Cameron wrote:
> On Tue, 4 Jul 2017 12:40:33 +0200
> Geert Uytterhoeven <[email protected]> wrote:
>
> > Hi Nicholas,
> >
> > On Sun, May 14, 2017 at 10:43 AM, Nicholas Mc Guire <[email protected]> wrote:
> > > If the timeout-case prints a warning message then probably the interrupted
> > > case should also. Further, wait_for_completion_interruptible_timeout()
> > > returns long not int.
> > >
> > > Fixes: commit 03b262f2bbf4 ("iio:pressure: initial zpa2326 barometer support")
> > > Signed-off-by: Nicholas Mc Guire <[email protected]>
> > > ---
> > >
> > > The original control-flow was technically not wrong just confusing and a bit
> > > complicated. Not clear if reporting the interrupted case actually is useful,
> > > but given that the timeout is relatively long (200ms) it is not that unlikely
> > > so differentiating the cases seems helpful.
> > >
> > > Patch was compile-tested with: x86_64_defconfig + CONFIG_IIO=m, CONFIG_ZPA2326=m
> > >
> > > Patch is against v4.11 (localversion-next is next-20170512)
> > >
> > > drivers/iio/pressure/zpa2326.c | 17 ++++++++++-------
> > > 1 file changed, 10 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/drivers/iio/pressure/zpa2326.c b/drivers/iio/pressure/zpa2326.c
> > > index e58a0ad..617926f 100644
> > > --- a/drivers/iio/pressure/zpa2326.c
> > > +++ b/drivers/iio/pressure/zpa2326.c
> > > @@ -867,12 +867,13 @@ static int zpa2326_wait_oneshot_completion(const struct iio_dev *indio_dev,
> > > {
> > > int ret;
> > > unsigned int val;
> > > + long timeout;
> > >
> > > zpa2326_dbg(indio_dev, "waiting for one shot completion interrupt");
> > >
> > > - ret = wait_for_completion_interruptible_timeout(
> > > + timeout = wait_for_completion_interruptible_timeout(
> > > &private->data_ready, ZPA2326_CONVERSION_JIFFIES);
> > > - if (ret > 0)
> > > + if (timeout > 0)
> >
> > Check for strict positive timeout.
> >
> > > /*
> > > * Interrupt handler completed before timeout: return operation
> > > * status.
> > > @@ -882,13 +883,15 @@ static int zpa2326_wait_oneshot_completion(const struct iio_dev *indio_dev,
> > > /* Clear all interrupts just to be sure. */
> > > regmap_read(private->regmap, ZPA2326_INT_SOURCE_REG, &val);
> > >
> > > - if (!ret)
> > > + if (!timeout) {
> >
> > Check for zero timeout.
> >
> > > /* Timed out. */
> > > + zpa2326_warn(indio_dev, "no one shot interrupt occurred (%ld)",
> > > + timeout);
> > > ret = -ETIME;
> > > -
> > > - if (ret != -ERESTARTSYS)
> > > - zpa2326_warn(indio_dev, "no one shot interrupt occurred (%d)",
> > > - ret);
> > > + } else if (timeout < 0) {
> >
> > So if we get here, timeout is always strict negative, so the check can
> > be removed.
> >
> > > + zpa2326_warn(indio_dev, "wait for one shot interrupt canceled");
> > > + ret = -ERESTARTSYS;
> > > + }
> > >
> > > return ret;
> >
> > But gcc-4.1.2 is not smart enough:
> >
> > drivers/iio/pressure/zpa2326.c:868: warning: ???ret??? may be used
> > uninitialized in this function
> Good analysis. Care to send the obvious patch?
>
Thanks Geert for finding that - yes ret needs to be
initialized to 0 here, success case as documented in
the header of zpa2326_wait_oneshot_completion -
interestingly enough gcc gcc (Debian 4.9.2-10) 4.9.2
does not flag this uninitioalized variable !
thx!
hofrat
Hi Nicholas,
On Wed, Jul 5, 2017 at 9:37 AM, Nicholas Mc Guire <[email protected]> wrote:
> On Tue, Jul 04, 2017 at 08:08:53PM +0100, Jonathan Cameron wrote:
>> On Tue, 4 Jul 2017 12:40:33 +0200
>> Geert Uytterhoeven <[email protected]> wrote:
>> > On Sun, May 14, 2017 at 10:43 AM, Nicholas Mc Guire <[email protected]> wrote:
>> > > If the timeout-case prints a warning message then probably the interrupted
>> > > case should also. Further, wait_for_completion_interruptible_timeout()
>> > > returns long not int.
>> > >
>> > > Fixes: commit 03b262f2bbf4 ("iio:pressure: initial zpa2326 barometer support")
>> > > Signed-off-by: Nicholas Mc Guire <[email protected]>
>> > > ---
>> > >
>> > > The original control-flow was technically not wrong just confusing and a bit
>> > > complicated. Not clear if reporting the interrupted case actually is useful,
>> > > but given that the timeout is relatively long (200ms) it is not that unlikely
>> > > so differentiating the cases seems helpful.
>> > >
>> > > Patch was compile-tested with: x86_64_defconfig + CONFIG_IIO=m, CONFIG_ZPA2326=m
>> > >
>> > > Patch is against v4.11 (localversion-next is next-20170512)
>> > >
>> > > drivers/iio/pressure/zpa2326.c | 17 ++++++++++-------
>> > > 1 file changed, 10 insertions(+), 7 deletions(-)
>> > >
>> > > diff --git a/drivers/iio/pressure/zpa2326.c b/drivers/iio/pressure/zpa2326.c
>> > > index e58a0ad..617926f 100644
>> > > --- a/drivers/iio/pressure/zpa2326.c
>> > > +++ b/drivers/iio/pressure/zpa2326.c
>> > > @@ -867,12 +867,13 @@ static int zpa2326_wait_oneshot_completion(const struct iio_dev *indio_dev,
>> > > {
>> > > int ret;
>> > > unsigned int val;
>> > > + long timeout;
>> > >
>> > > zpa2326_dbg(indio_dev, "waiting for one shot completion interrupt");
>> > >
>> > > - ret = wait_for_completion_interruptible_timeout(
>> > > + timeout = wait_for_completion_interruptible_timeout(
>> > > &private->data_ready, ZPA2326_CONVERSION_JIFFIES);
>> > > - if (ret > 0)
>> > > + if (timeout > 0)
>> >
>> > Check for strict positive timeout.
>> >
>> > > /*
>> > > * Interrupt handler completed before timeout: return operation
>> > > * status.
>> > > @@ -882,13 +883,15 @@ static int zpa2326_wait_oneshot_completion(const struct iio_dev *indio_dev,
>> > > /* Clear all interrupts just to be sure. */
>> > > regmap_read(private->regmap, ZPA2326_INT_SOURCE_REG, &val);
>> > >
>> > > - if (!ret)
>> > > + if (!timeout) {
>> >
>> > Check for zero timeout.
>> >
>> > > /* Timed out. */
>> > > + zpa2326_warn(indio_dev, "no one shot interrupt occurred (%ld)",
>> > > + timeout);
>> > > ret = -ETIME;
>> > > -
>> > > - if (ret != -ERESTARTSYS)
>> > > - zpa2326_warn(indio_dev, "no one shot interrupt occurred (%d)",
>> > > - ret);
>> > > + } else if (timeout < 0) {
>> >
>> > So if we get here, timeout is always strict negative, so the check can
>> > be removed.
>> >
>> > > + zpa2326_warn(indio_dev, "wait for one shot interrupt canceled");
>> > > + ret = -ERESTARTSYS;
>> > > + }
>> > >
>> > > return ret;
>> >
>> > But gcc-4.1.2 is not smart enough:
>> >
>> > drivers/iio/pressure/zpa2326.c:868: warning: ???ret??? may be used
>> > uninitialized in this function
>> Good analysis. Care to send the obvious patch?
>>
> Thanks Geert for finding that - yes ret needs to be
> initialized to 0 here, success case as documented in
> the header of zpa2326_wait_oneshot_completion -
No, ret does not need to be initialized to 0, as it would prevent the warning
from reappearing in case of future logic errors.
Instead the last "if" should be removed, as it's always true.
Will send a patch, as requested by Jonathan.
> interestingly enough gcc gcc (Debian 4.9.2-10) 4.9.2
> does not flag this uninitioalized variable !
Only very old or very new versions of gcc do that.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
On Wed, 5 Jul 2017 07:37:05 +0000
Nicholas Mc Guire <[email protected]> wrote:
> On Tue, Jul 04, 2017 at 08:08:53PM +0100, Jonathan Cameron wrote:
> > On Tue, 4 Jul 2017 12:40:33 +0200
> > Geert Uytterhoeven <[email protected]> wrote:
> >
> > > Hi Nicholas,
> > >
> > > On Sun, May 14, 2017 at 10:43 AM, Nicholas Mc Guire
> > > <[email protected]> wrote:
> > > > If the timeout-case prints a warning message then probably the
> > > > interrupted case should also. Further,
> > > > wait_for_completion_interruptible_timeout() returns long not
> > > > int.
> > > >
> > > > Fixes: commit 03b262f2bbf4 ("iio:pressure: initial zpa2326
> > > > barometer support") Signed-off-by: Nicholas Mc Guire
> > > > <[email protected]> ---
> > > >
> > > > The original control-flow was technically not wrong just
> > > > confusing and a bit complicated. Not clear if reporting the
> > > > interrupted case actually is useful, but given that the timeout
> > > > is relatively long (200ms) it is not that unlikely so
> > > > differentiating the cases seems helpful.
> > > >
> > > > Patch was compile-tested with: x86_64_defconfig + CONFIG_IIO=m,
> > > > CONFIG_ZPA2326=m
> > > >
> > > > Patch is against v4.11 (localversion-next is next-20170512)
> > > >
> > > > drivers/iio/pressure/zpa2326.c | 17 ++++++++++-------
> > > > 1 file changed, 10 insertions(+), 7 deletions(-)
> > > >
> > > > diff --git a/drivers/iio/pressure/zpa2326.c
> > > > b/drivers/iio/pressure/zpa2326.c index e58a0ad..617926f 100644
> > > > --- a/drivers/iio/pressure/zpa2326.c
> > > > +++ b/drivers/iio/pressure/zpa2326.c
> > > > @@ -867,12 +867,13 @@ static int
> > > > zpa2326_wait_oneshot_completion(const struct iio_dev
> > > > *indio_dev, { int ret;
> > > > unsigned int val;
> > > > + long timeout;
> > > >
> > > > zpa2326_dbg(indio_dev, "waiting for one shot completion
> > > > interrupt");
> > > >
> > > > - ret = wait_for_completion_interruptible_timeout(
> > > > + timeout = wait_for_completion_interruptible_timeout(
> > > > &private->data_ready,
> > > > ZPA2326_CONVERSION_JIFFIES);
> > > > - if (ret > 0)
> > > > + if (timeout > 0)
> > >
> > > Check for strict positive timeout.
> > >
> > > > /*
> > > > * Interrupt handler completed before timeout:
> > > > return operation
> > > > * status.
> > > > @@ -882,13 +883,15 @@ static int
> > > > zpa2326_wait_oneshot_completion(const struct iio_dev
> > > > *indio_dev, /* Clear all interrupts just to be sure. */
> > > > regmap_read(private->regmap, ZPA2326_INT_SOURCE_REG, &val);
> > > >
> > > > - if (!ret)
> > > > + if (!timeout) {
> > >
> > > Check for zero timeout.
> > >
> > > > /* Timed out. */
> > > > + zpa2326_warn(indio_dev, "no one shot interrupt
> > > > occurred (%ld)",
> > > > + timeout);
> > > > ret = -ETIME;
> > > > -
> > > > - if (ret != -ERESTARTSYS)
> > > > - zpa2326_warn(indio_dev, "no one shot interrupt
> > > > occurred (%d)",
> > > > - ret);
> > > > + } else if (timeout < 0) {
> > >
> > > So if we get here, timeout is always strict negative, so the
> > > check can be removed.
> > >
> > > > + zpa2326_warn(indio_dev, "wait for one shot
> > > > interrupt canceled");
> > > > + ret = -ERESTARTSYS;
> > > > + }
> > > >
> > > > return ret;
> > >
> > > But gcc-4.1.2 is not smart enough:
> > >
> > > drivers/iio/pressure/zpa2326.c:868: warning: ???ret??? may be used
> > > uninitialized in this function
> > Good analysis. Care to send the obvious patch?
> >
> Thanks Geert for finding that - yes ret needs to be
> initialized to 0 here, success case as documented in
> the header of zpa2326_wait_oneshot_completion -
> interestingly enough gcc gcc (Debian 4.9.2-10) 4.9.2
> does not flag this uninitioalized variable !
I think Geert's analysis also suggests that you can just drop the last
conditional without changing the code. gcc should be fine with that
Jonathan
>
> thx!
> hofrat
> --
> To unsubscribe from this list: send the line "unsubscribe linux-iio"
> in the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, Jul 05, 2017 at 10:02:17AM +0200, Geert Uytterhoeven wrote:
> Hi Nicholas,
>
> On Wed, Jul 5, 2017 at 9:37 AM, Nicholas Mc Guire <[email protected]> wrote:
> > On Tue, Jul 04, 2017 at 08:08:53PM +0100, Jonathan Cameron wrote:
> >> On Tue, 4 Jul 2017 12:40:33 +0200
> >> Geert Uytterhoeven <[email protected]> wrote:
> >> > On Sun, May 14, 2017 at 10:43 AM, Nicholas Mc Guire <[email protected]> wrote:
> >> > > If the timeout-case prints a warning message then probably the interrupted
> >> > > case should also. Further, wait_for_completion_interruptible_timeout()
> >> > > returns long not int.
> >> > >
> >> > > Fixes: commit 03b262f2bbf4 ("iio:pressure: initial zpa2326 barometer support")
> >> > > Signed-off-by: Nicholas Mc Guire <[email protected]>
> >> > > ---
> >> > >
> >> > > The original control-flow was technically not wrong just confusing and a bit
> >> > > complicated. Not clear if reporting the interrupted case actually is useful,
> >> > > but given that the timeout is relatively long (200ms) it is not that unlikely
> >> > > so differentiating the cases seems helpful.
> >> > >
> >> > > Patch was compile-tested with: x86_64_defconfig + CONFIG_IIO=m, CONFIG_ZPA2326=m
> >> > >
> >> > > Patch is against v4.11 (localversion-next is next-20170512)
> >> > >
> >> > > drivers/iio/pressure/zpa2326.c | 17 ++++++++++-------
> >> > > 1 file changed, 10 insertions(+), 7 deletions(-)
> >> > >
> >> > > diff --git a/drivers/iio/pressure/zpa2326.c b/drivers/iio/pressure/zpa2326.c
> >> > > index e58a0ad..617926f 100644
> >> > > --- a/drivers/iio/pressure/zpa2326.c
> >> > > +++ b/drivers/iio/pressure/zpa2326.c
> >> > > @@ -867,12 +867,13 @@ static int zpa2326_wait_oneshot_completion(const struct iio_dev *indio_dev,
> >> > > {
> >> > > int ret;
> >> > > unsigned int val;
> >> > > + long timeout;
> >> > >
> >> > > zpa2326_dbg(indio_dev, "waiting for one shot completion interrupt");
> >> > >
> >> > > - ret = wait_for_completion_interruptible_timeout(
> >> > > + timeout = wait_for_completion_interruptible_timeout(
> >> > > &private->data_ready, ZPA2326_CONVERSION_JIFFIES);
> >> > > - if (ret > 0)
> >> > > + if (timeout > 0)
> >> >
> >> > Check for strict positive timeout.
> >> >
> >> > > /*
> >> > > * Interrupt handler completed before timeout: return operation
> >> > > * status.
> >> > > @@ -882,13 +883,15 @@ static int zpa2326_wait_oneshot_completion(const struct iio_dev *indio_dev,
> >> > > /* Clear all interrupts just to be sure. */
> >> > > regmap_read(private->regmap, ZPA2326_INT_SOURCE_REG, &val);
> >> > >
> >> > > - if (!ret)
> >> > > + if (!timeout) {
> >> >
> >> > Check for zero timeout.
> >> >
> >> > > /* Timed out. */
> >> > > + zpa2326_warn(indio_dev, "no one shot interrupt occurred (%ld)",
> >> > > + timeout);
> >> > > ret = -ETIME;
> >> > > -
> >> > > - if (ret != -ERESTARTSYS)
> >> > > - zpa2326_warn(indio_dev, "no one shot interrupt occurred (%d)",
> >> > > - ret);
> >> > > + } else if (timeout < 0) {
> >> >
> >> > So if we get here, timeout is always strict negative, so the check can
> >> > be removed.
> >> >
> >> > > + zpa2326_warn(indio_dev, "wait for one shot interrupt canceled");
> >> > > + ret = -ERESTARTSYS;
> >> > > + }
> >> > >
> >> > > return ret;
> >> >
> >> > But gcc-4.1.2 is not smart enough:
> >> >
> >> > drivers/iio/pressure/zpa2326.c:868: warning: ???ret??? may be used
> >> > uninitialized in this function
> >> Good analysis. Care to send the obvious patch?
> >>
> > Thanks Geert for finding that - yes ret needs to be
> > initialized to 0 here, success case as documented in
> > the header of zpa2326_wait_oneshot_completion -
>
> No, ret does not need to be initialized to 0, as it would prevent the warning
> from reappearing in case of future logic errors.
>
> Instead the last "if" should be removed, as it's always true.
> Will send a patch, as requested by Jonathan.
>
hmm... the if can be removed but then it would be two return statements
and one could simply drop ret all together
if (!timeout) {
/* Timed out. */
zpa2326_warn(indio_dev, "no one shot interrupt occurred (%ld)",
timeout);
return -ETIME;
}
zpa2326_warn(indio_dev, "wait for one shot interrupt cancelled");
return -ERESTARTSYS
but I assumed that kernel code should try to not end up
with too many exit points, in which case the if is needed
and the warning could be elimnated by initializing ret to 0
even if that is more or less usless.
> > interestingly enough gcc gcc (Debian 4.9.2-10) 4.9.2
> > does not flag this uninitioalized variable !
>
> Only very old or very new versions of gcc do that.
>
thanks - so I need to upgrad my gcc as the compile-checking
will fail to catch uninitilized vars then, atleast in
some cases.
thx!
hofrat
On Wed, 5 Jul 2017 08:55:47 +0000
Nicholas Mc Guire <[email protected]> wrote:
> On Wed, Jul 05, 2017 at 10:02:17AM +0200, Geert Uytterhoeven wrote:
> > Hi Nicholas,
> >
> > On Wed, Jul 5, 2017 at 9:37 AM, Nicholas Mc Guire
> > <[email protected]> wrote:
> > > On Tue, Jul 04, 2017 at 08:08:53PM +0100, Jonathan Cameron
> > > wrote:
> > >> On Tue, 4 Jul 2017 12:40:33 +0200
> > >> Geert Uytterhoeven <[email protected]> wrote:
> > >> > On Sun, May 14, 2017 at 10:43 AM, Nicholas Mc Guire
> > >> > <[email protected]> wrote:
> > >> > > If the timeout-case prints a warning message then probably
> > >> > > the interrupted case should also. Further,
> > >> > > wait_for_completion_interruptible_timeout() returns long not
> > >> > > int.
> > >> > >
> > >> > > Fixes: commit 03b262f2bbf4 ("iio:pressure: initial zpa2326
> > >> > > barometer support") Signed-off-by: Nicholas Mc Guire
> > >> > > <[email protected]> ---
> > >> > >
> > >> > > The original control-flow was technically not wrong just
> > >> > > confusing and a bit complicated. Not clear if reporting the
> > >> > > interrupted case actually is useful, but given that the
> > >> > > timeout is relatively long (200ms) it is not that unlikely
> > >> > > so differentiating the cases seems helpful.
> > >> > >
> > >> > > Patch was compile-tested with: x86_64_defconfig +
> > >> > > CONFIG_IIO=m, CONFIG_ZPA2326=m
> > >> > >
> > >> > > Patch is against v4.11 (localversion-next is next-20170512)
> > >> > >
> > >> > > drivers/iio/pressure/zpa2326.c | 17 ++++++++++-------
> > >> > > 1 file changed, 10 insertions(+), 7 deletions(-)
> > >> > >
> > >> > > diff --git a/drivers/iio/pressure/zpa2326.c
> > >> > > b/drivers/iio/pressure/zpa2326.c index e58a0ad..617926f
> > >> > > 100644 --- a/drivers/iio/pressure/zpa2326.c
> > >> > > +++ b/drivers/iio/pressure/zpa2326.c
> > >> > > @@ -867,12 +867,13 @@ static int
> > >> > > zpa2326_wait_oneshot_completion(const struct iio_dev
> > >> > > *indio_dev, { int ret;
> > >> > > unsigned int val;
> > >> > > + long timeout;
> > >> > >
> > >> > > zpa2326_dbg(indio_dev, "waiting for one shot
> > >> > > completion interrupt");
> > >> > >
> > >> > > - ret = wait_for_completion_interruptible_timeout(
> > >> > > + timeout = wait_for_completion_interruptible_timeout(
> > >> > > &private->data_ready,
> > >> > > ZPA2326_CONVERSION_JIFFIES);
> > >> > > - if (ret > 0)
> > >> > > + if (timeout > 0)
> > >> >
> > >> > Check for strict positive timeout.
> > >> >
> > >> > > /*
> > >> > > * Interrupt handler completed before
> > >> > > timeout: return operation
> > >> > > * status.
> > >> > > @@ -882,13 +883,15 @@ static int
> > >> > > zpa2326_wait_oneshot_completion(const struct iio_dev
> > >> > > *indio_dev, /* Clear all interrupts just to be sure. */
> > >> > > regmap_read(private->regmap, ZPA2326_INT_SOURCE_REG, &val);
> > >> > >
> > >> > > - if (!ret)
> > >> > > + if (!timeout) {
> > >> >
> > >> > Check for zero timeout.
> > >> >
> > >> > > /* Timed out. */
> > >> > > + zpa2326_warn(indio_dev, "no one shot
> > >> > > interrupt occurred (%ld)",
> > >> > > + timeout);
> > >> > > ret = -ETIME;
> > >> > > -
> > >> > > - if (ret != -ERESTARTSYS)
> > >> > > - zpa2326_warn(indio_dev, "no one shot
> > >> > > interrupt occurred (%d)",
> > >> > > - ret);
> > >> > > + } else if (timeout < 0) {
> > >> >
> > >> > So if we get here, timeout is always strict negative, so the
> > >> > check can be removed.
> > >> >
> > >> > > + zpa2326_warn(indio_dev, "wait for one shot
> > >> > > interrupt canceled");
> > >> > > + ret = -ERESTARTSYS;
> > >> > > + }
> > >> > >
> > >> > > return ret;
> > >> >
> > >> > But gcc-4.1.2 is not smart enough:
> > >> >
> > >> > drivers/iio/pressure/zpa2326.c:868: warning: ???ret??? may be
> > >> > used uninitialized in this function
> > >> Good analysis. Care to send the obvious patch?
> > >>
> > > Thanks Geert for finding that - yes ret needs to be
> > > initialized to 0 here, success case as documented in
> > > the header of zpa2326_wait_oneshot_completion -
> >
> > No, ret does not need to be initialized to 0, as it would prevent
> > the warning from reappearing in case of future logic errors.
> >
> > Instead the last "if" should be removed, as it's always true.
> > Will send a patch, as requested by Jonathan.
> >
> hmm... the if can be removed but then it would be two return
> statements and one could simply drop ret all together
>
> if (!timeout) {
> /* Timed out. */
> zpa2326_warn(indio_dev, "no one shot interrupt
> occurred (%ld)", timeout);
> return -ETIME;
> }
> zpa2326_warn(indio_dev, "wait for one shot interrupt
> cancelled"); return -ERESTARTSYS
>
> but I assumed that kernel code should try to not end up
> with too many exit points, in which case the if is needed
> and the warning could be elimnated by initializing ret to 0
> even if that is more or less usless.
Usual rule of thumb for kernel style is that if you have cleanup to
do (releasing locks etc) then it should be done at a common location.
If there is no cleanup then you should return directly.
Jonathan
>
> > > interestingly enough gcc gcc (Debian 4.9.2-10) 4.9.2
> > > does not flag this uninitioalized variable !
> >
> > Only very old or very new versions of gcc do that.
> >
> thanks - so I need to upgrad my gcc as the compile-checking
> will fail to catch uninitilized vars then, atleast in
> some cases.
>
> thx!
> hofrat
> --
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> in the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, Jul 05, 2017 at 06:06:09PM +0800, Jonathan Cameron wrote:
> On Wed, 5 Jul 2017 08:55:47 +0000
> Nicholas Mc Guire <[email protected]> wrote:
>
> > On Wed, Jul 05, 2017 at 10:02:17AM +0200, Geert Uytterhoeven wrote:
> > > Hi Nicholas,
> > >
> > > On Wed, Jul 5, 2017 at 9:37 AM, Nicholas Mc Guire
> > > <[email protected]> wrote:
> > > > On Tue, Jul 04, 2017 at 08:08:53PM +0100, Jonathan Cameron
> > > > wrote:
> > > >> On Tue, 4 Jul 2017 12:40:33 +0200
> > > >> Geert Uytterhoeven <[email protected]> wrote:
> > > >> > On Sun, May 14, 2017 at 10:43 AM, Nicholas Mc Guire
> > > >> > <[email protected]> wrote:
> > > >> > > If the timeout-case prints a warning message then probably
> > > >> > > the interrupted case should also. Further,
> > > >> > > wait_for_completion_interruptible_timeout() returns long not
> > > >> > > int.
> > > >> > >
> > > >> > > Fixes: commit 03b262f2bbf4 ("iio:pressure: initial zpa2326
> > > >> > > barometer support") Signed-off-by: Nicholas Mc Guire
> > > >> > > <[email protected]> ---
> > > >> > >
> > > >> > > The original control-flow was technically not wrong just
> > > >> > > confusing and a bit complicated. Not clear if reporting the
> > > >> > > interrupted case actually is useful, but given that the
> > > >> > > timeout is relatively long (200ms) it is not that unlikely
> > > >> > > so differentiating the cases seems helpful.
> > > >> > >
> > > >> > > Patch was compile-tested with: x86_64_defconfig +
> > > >> > > CONFIG_IIO=m, CONFIG_ZPA2326=m
> > > >> > >
> > > >> > > Patch is against v4.11 (localversion-next is next-20170512)
> > > >> > >
> > > >> > > drivers/iio/pressure/zpa2326.c | 17 ++++++++++-------
> > > >> > > 1 file changed, 10 insertions(+), 7 deletions(-)
> > > >> > >
> > > >> > > diff --git a/drivers/iio/pressure/zpa2326.c
> > > >> > > b/drivers/iio/pressure/zpa2326.c index e58a0ad..617926f
> > > >> > > 100644 --- a/drivers/iio/pressure/zpa2326.c
> > > >> > > +++ b/drivers/iio/pressure/zpa2326.c
> > > >> > > @@ -867,12 +867,13 @@ static int
> > > >> > > zpa2326_wait_oneshot_completion(const struct iio_dev
> > > >> > > *indio_dev, { int ret;
> > > >> > > unsigned int val;
> > > >> > > + long timeout;
> > > >> > >
> > > >> > > zpa2326_dbg(indio_dev, "waiting for one shot
> > > >> > > completion interrupt");
> > > >> > >
> > > >> > > - ret = wait_for_completion_interruptible_timeout(
> > > >> > > + timeout = wait_for_completion_interruptible_timeout(
> > > >> > > &private->data_ready,
> > > >> > > ZPA2326_CONVERSION_JIFFIES);
> > > >> > > - if (ret > 0)
> > > >> > > + if (timeout > 0)
> > > >> >
> > > >> > Check for strict positive timeout.
> > > >> >
> > > >> > > /*
> > > >> > > * Interrupt handler completed before
> > > >> > > timeout: return operation
> > > >> > > * status.
> > > >> > > @@ -882,13 +883,15 @@ static int
> > > >> > > zpa2326_wait_oneshot_completion(const struct iio_dev
> > > >> > > *indio_dev, /* Clear all interrupts just to be sure. */
> > > >> > > regmap_read(private->regmap, ZPA2326_INT_SOURCE_REG, &val);
> > > >> > >
> > > >> > > - if (!ret)
> > > >> > > + if (!timeout) {
> > > >> >
> > > >> > Check for zero timeout.
> > > >> >
> > > >> > > /* Timed out. */
> > > >> > > + zpa2326_warn(indio_dev, "no one shot
> > > >> > > interrupt occurred (%ld)",
> > > >> > > + timeout);
> > > >> > > ret = -ETIME;
> > > >> > > -
> > > >> > > - if (ret != -ERESTARTSYS)
> > > >> > > - zpa2326_warn(indio_dev, "no one shot
> > > >> > > interrupt occurred (%d)",
> > > >> > > - ret);
> > > >> > > + } else if (timeout < 0) {
> > > >> >
> > > >> > So if we get here, timeout is always strict negative, so the
> > > >> > check can be removed.
> > > >> >
> > > >> > > + zpa2326_warn(indio_dev, "wait for one shot
> > > >> > > interrupt canceled");
> > > >> > > + ret = -ERESTARTSYS;
> > > >> > > + }
> > > >> > >
> > > >> > > return ret;
> > > >> >
> > > >> > But gcc-4.1.2 is not smart enough:
> > > >> >
> > > >> > drivers/iio/pressure/zpa2326.c:868: warning: ???ret??? may be
> > > >> > used uninitialized in this function
> > > >> Good analysis. Care to send the obvious patch?
> > > >>
> > > > Thanks Geert for finding that - yes ret needs to be
> > > > initialized to 0 here, success case as documented in
> > > > the header of zpa2326_wait_oneshot_completion -
> > >
> > > No, ret does not need to be initialized to 0, as it would prevent
> > > the warning from reappearing in case of future logic errors.
> > >
> > > Instead the last "if" should be removed, as it's always true.
> > > Will send a patch, as requested by Jonathan.
> > >
> > hmm... the if can be removed but then it would be two return
> > statements and one could simply drop ret all together
> >
> > if (!timeout) {
> > /* Timed out. */
> > zpa2326_warn(indio_dev, "no one shot interrupt
> > occurred (%ld)", timeout);
> > return -ETIME;
> > }
> > zpa2326_warn(indio_dev, "wait for one shot interrupt
> > cancelled"); return -ERESTARTSYS
> >
> > but I assumed that kernel code should try to not end up
> > with too many exit points, in which case the if is needed
> > and the warning could be elimnated by initializing ret to 0
> > even if that is more or less usless.
> Usual rule of thumb for kernel style is that if you have cleanup to
> do (releasing locks etc) then it should be done at a common location.
> If there is no cleanup then you should return directly.
>
yup - just rechecked "7) Centralized exiting of functions" in coding-style.rst
so the solution I posted was wrong - thanks for the clarification !
thx!
hforat