[PATCH net-next] net: ipa: always inline ipa_aggr_granularity_val()

It isn't required, but all callers of ipa_aggr_granularity_val()
pass a constant value (IPA_AGGR_GRANULARITY) as the usec argument.
Two of those callers are in ipa_validate_build(), with the result
being passed to BUILD_BUG_ON().

Evidently the "sparc64-linux-gcc" compiler (at least) doesn't always
inline ipa_aggr_granularity_val(), so the result of the function is
not constant at compile time, and that leads to build errors.

Define the function with the __always_inline attribute to avoid the
errors.  And given that the function is inline, we can switch the
WARN_ON() there to be BUILD_BUG_ON().

Fixes: 5bc5588466a1f ("net: ipa: use WARN_ON() rather than assertions")
Reported-by: kernel test robot <redacted>
Signed-off-by: Alex Elder <redacted>
---

David/Jakub, this fixes a bug in a commit in net-next/master.  -Alex

 drivers/net/ipa/ipa_main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ipa/ipa_main.c b/drivers/net/ipa/ipa_main.c
index 25bbb456e0078..f90b3521e266b 100644
--- a/drivers/net/ipa/ipa_main.c
+++ b/drivers/net/ipa/ipa_main.c

@@ -255,9 +255,9 @@ ipa_hardware_config_qsb(struct ipa *ipa, const struct ipa_data *data)
  * less than the number of timer ticks in the requested period.  0 is not
  * a valid granularity value.
  */
-static u32 ipa_aggr_granularity_val(u32 usec)
+static __always_inline u32 ipa_aggr_granularity_val(u32 usec)
 {
-	WARN_ON(!usec);
+	BUILD_BUG_ON(!usec);
 
 	return DIV_ROUND_CLOSEST(usec * TIMER_FREQUENCY, USEC_PER_SEC) - 1;
 }

-- 
2.27.0

On Tue, Aug 10, 2021 at 11:02:13AM -0500, Alex Elder wrote:

So what exactly are you checking here if all callers pass same value?
It is in-kernel API, declared as static inside one module. There is no
need to protect from itself.

Thanks

 
 	return DIV_ROUND_CLOSEST(usec * TIMER_FREQUENCY, USEC_PER_SEC) - 1;
 }
-- 
2.27.0

On 8/11/21 7:02 AM, Leon Romanovsky wrote:

On Tue, Aug 10, 2021 at 11:02:13AM -0500, Alex Elder wrote:

quoted

It isn't required, but all callers of ipa_aggr_granularity_val()
pass a constant value (IPA_AGGR_GRANULARITY) as the usec argument.
Two of those callers are in ipa_validate_build(), with the result
being passed to BUILD_BUG_ON().

Evidently the "sparc64-linux-gcc" compiler (at least) doesn't always
inline ipa_aggr_granularity_val(), so the result of the function is
not constant at compile time, and that leads to build errors.

Define the function with the __always_inline attribute to avoid the
errors.  And given that the function is inline, we can switch the
WARN_ON() there to be BUILD_BUG_ON().

Fixes: 5bc5588466a1f ("net: ipa: use WARN_ON() rather than assertions")
Reported-by: kernel test robot <redacted>
Signed-off-by: Alex Elder <redacted>
---

David/Jakub, this fixes a bug in a commit in net-next/master.  -Alex

 drivers/net/ipa/ipa_main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ipa/ipa_main.c b/drivers/net/ipa/ipa_main.c
index 25bbb456e0078..f90b3521e266b 100644
--- a/drivers/net/ipa/ipa_main.c
+++ b/drivers/net/ipa/ipa_main.c

@@ -255,9 +255,9 @@ ipa_hardware_config_qsb(struct ipa *ipa, const struct ipa_data *data)
  * less than the number of timer ticks in the requested period.  0 is not
  * a valid granularity value.
  */
-static u32 ipa_aggr_granularity_val(u32 usec)
+static __always_inline u32 ipa_aggr_granularity_val(u32 usec)
 {
-	WARN_ON(!usec);
+	BUILD_BUG_ON(!usec);

So what exactly are you checking here if all callers pass same value?
It is in-kernel API, declared as static inside one module. There is no
need to protect from itself.

Yeah that's a good point.  It can just as well be removed.
I think the check was added before I knew it was only going
to be used with a single constant value.  That said, the
point was to check at runtime a required constraint.

I'll post version 2 that simply removes it.  Thanks.

					-Alex

Thanks

quoted

 
 	return DIV_ROUND_CLOSEST(usec * TIMER_FREQUENCY, USEC_PER_SEC) - 1;
 }
-- 
2.27.0

On Wed, Aug 11, 2021 at 07:06:01AM -0500, Alex Elder wrote:

On 8/11/21 7:02 AM, Leon Romanovsky wrote:

quoted

On Tue, Aug 10, 2021 at 11:02:13AM -0500, Alex Elder wrote:

quoted

It isn't required, but all callers of ipa_aggr_granularity_val()
pass a constant value (IPA_AGGR_GRANULARITY) as the usec argument.
Two of those callers are in ipa_validate_build(), with the result
being passed to BUILD_BUG_ON().

Evidently the "sparc64-linux-gcc" compiler (at least) doesn't always
inline ipa_aggr_granularity_val(), so the result of the function is
not constant at compile time, and that leads to build errors.

Define the function with the __always_inline attribute to avoid the
errors.  And given that the function is inline, we can switch the
WARN_ON() there to be BUILD_BUG_ON().

Fixes: 5bc5588466a1f ("net: ipa: use WARN_ON() rather than assertions")
Reported-by: kernel test robot <redacted>
Signed-off-by: Alex Elder <redacted>
---

David/Jakub, this fixes a bug in a commit in net-next/master.  -Alex

 drivers/net/ipa/ipa_main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ipa/ipa_main.c b/drivers/net/ipa/ipa_main.c
index 25bbb456e0078..f90b3521e266b 100644
--- a/drivers/net/ipa/ipa_main.c
+++ b/drivers/net/ipa/ipa_main.c

@@ -255,9 +255,9 @@ ipa_hardware_config_qsb(struct ipa *ipa, const struct ipa_data *data)
  * less than the number of timer ticks in the requested period.  0 is not
  * a valid granularity value.
  */
-static u32 ipa_aggr_granularity_val(u32 usec)
+static __always_inline u32 ipa_aggr_granularity_val(u32 usec)
 {
-	WARN_ON(!usec);
+	BUILD_BUG_ON(!usec);

So what exactly are you checking here if all callers pass same value?
It is in-kernel API, declared as static inside one module. There is no
need to protect from itself.

Yeah that's a good point.  It can just as well be removed.
I think the check was added before I knew it was only going
to be used with a single constant value.  That said, the
point was to check at runtime a required constraint.

I'll post version 2 that simply removes it.  Thanks.

Thanks

					-Alex

quoted

Thanks

quoted

 
 	return DIV_ROUND_CLOSEST(usec * TIMER_FREQUENCY, USEC_PER_SEC) - 1;
 }
-- 
2.27.0