| Message ID | 20200714145049.2496163-9-lee.jones@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Rid W=1 warnings in CPUFreq | expand |
On Tue, Jul 14, 2020 at 4:51 PM Lee Jones <lee.jones@linaro.org> wrote: > > If we fail to use a variable, even a 'dummy' one, then the compiler > complains that it is set but not used. We know this is fine, so we > set it to its own value here. Which is kind of ugly in my personal view. I hope that the compiler will actually optimize the extra code away ... > Fixes the following W=1 kernel build warning(s): Well, "Makes the following ... warning(s) go away:" rather ... > drivers/cpufreq/acpi-cpufreq.c: In function ‘cpu_freq_read_intel’: > drivers/cpufreq/acpi-cpufreq.c:247:11: warning: variable ‘dummy’ set but not used [-Wunused-but-set-variable] > drivers/cpufreq/acpi-cpufreq.c: In function ‘cpu_freq_read_amd’: > drivers/cpufreq/acpi-cpufreq.c:265:11: warning: variable ‘dummy’ set but not used [-Wunused-but-set-variable] > > Cc: Andy Grover <andrew.grover@intel.com> > Cc: Paul Diefenbaugh <paul.s.diefenbaugh@intel.com> > Cc: Dominik Brodowski <linux@brodo.de> > Cc: Denis Sadykov <denis.m.sadykov@intel.com> > Signed-off-by: Lee Jones <lee.jones@linaro.org> > --- > drivers/cpufreq/acpi-cpufreq.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c > index 429e5a36c08a9..d38a693b48e03 100644 > --- a/drivers/cpufreq/acpi-cpufreq.c > +++ b/drivers/cpufreq/acpi-cpufreq.c > @@ -247,6 +247,7 @@ static u32 cpu_freq_read_intel(struct acpi_pct_register *not_used) > u32 val, dummy; > > rdmsr(MSR_IA32_PERF_CTL, val, dummy); > + dummy &= dummy; /* Silence set but not used warning */ > return val; > } > > @@ -264,6 +265,7 @@ static u32 cpu_freq_read_amd(struct acpi_pct_register *not_used) > u32 val, dummy; > > rdmsr(MSR_AMD_PERF_CTL, val, dummy); > + dummy &= dummy; /* Silence set but not used warning */ > return val; > } > > -- > 2.25.1 >
On 2020-07-14 17:03, Rafael J. Wysocki wrote: > On Tue, Jul 14, 2020 at 4:51 PM Lee Jones <lee.jones@linaro.org> wrote: >> >> If we fail to use a variable, even a 'dummy' one, then the compiler >> complains that it is set but not used. We know this is fine, so we >> set it to its own value here. > > Which is kind of ugly in my personal view. I hope that the compiler > will actually optimize the extra code away ... > >> Fixes the following W=1 kernel build warning(s): > > Well, "Makes the following ... warning(s) go away:" rather ... Isn't that what we have __maybe_unused and __always_unused for? Robin. >> drivers/cpufreq/acpi-cpufreq.c: In function ‘cpu_freq_read_intel’: >> drivers/cpufreq/acpi-cpufreq.c:247:11: warning: variable ‘dummy’ set but not used [-Wunused-but-set-variable] >> drivers/cpufreq/acpi-cpufreq.c: In function ‘cpu_freq_read_amd’: >> drivers/cpufreq/acpi-cpufreq.c:265:11: warning: variable ‘dummy’ set but not used [-Wunused-but-set-variable] >> >> Cc: Andy Grover <andrew.grover@intel.com> >> Cc: Paul Diefenbaugh <paul.s.diefenbaugh@intel.com> >> Cc: Dominik Brodowski <linux@brodo.de> >> Cc: Denis Sadykov <denis.m.sadykov@intel.com> >> Signed-off-by: Lee Jones <lee.jones@linaro.org> >> --- >> drivers/cpufreq/acpi-cpufreq.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c >> index 429e5a36c08a9..d38a693b48e03 100644 >> --- a/drivers/cpufreq/acpi-cpufreq.c >> +++ b/drivers/cpufreq/acpi-cpufreq.c >> @@ -247,6 +247,7 @@ static u32 cpu_freq_read_intel(struct acpi_pct_register *not_used) >> u32 val, dummy; >> >> rdmsr(MSR_IA32_PERF_CTL, val, dummy); >> + dummy &= dummy; /* Silence set but not used warning */ >> return val; >> } >> >> @@ -264,6 +265,7 @@ static u32 cpu_freq_read_amd(struct acpi_pct_register *not_used) >> u32 val, dummy; >> >> rdmsr(MSR_AMD_PERF_CTL, val, dummy); >> + dummy &= dummy; /* Silence set but not used warning */ >> return val; >> } >> >> -- >> 2.25.1 >> > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >
On Tue, 14 Jul 2020, Robin Murphy wrote: > On 2020-07-14 17:03, Rafael J. Wysocki wrote: > > On Tue, Jul 14, 2020 at 4:51 PM Lee Jones <lee.jones@linaro.org> wrote: > > > > > > If we fail to use a variable, even a 'dummy' one, then the compiler > > > complains that it is set but not used. We know this is fine, so we > > > set it to its own value here. > > > > Which is kind of ugly in my personal view. I hope that the compiler > > will actually optimize the extra code away ... > > > > > Fixes the following W=1 kernel build warning(s): > > > > Well, "Makes the following ... warning(s) go away:" rather ... > > Isn't that what we have __maybe_unused and __always_unused for? Yes, that would be better. I didn't know you could do that with standard variables. Will fix. > > > drivers/cpufreq/acpi-cpufreq.c: In function ‘cpu_freq_read_intel’: > > > drivers/cpufreq/acpi-cpufreq.c:247:11: warning: variable ‘dummy’ set but not used [-Wunused-but-set-variable] > > > drivers/cpufreq/acpi-cpufreq.c: In function ‘cpu_freq_read_amd’: > > > drivers/cpufreq/acpi-cpufreq.c:265:11: warning: variable ‘dummy’ set but not used [-Wunused-but-set-variable] > > > > > > Cc: Andy Grover <andrew.grover@intel.com> > > > Cc: Paul Diefenbaugh <paul.s.diefenbaugh@intel.com> > > > Cc: Dominik Brodowski <linux@brodo.de> > > > Cc: Denis Sadykov <denis.m.sadykov@intel.com> > > > Signed-off-by: Lee Jones <lee.jones@linaro.org> > > > --- > > > drivers/cpufreq/acpi-cpufreq.c | 2 ++ > > > 1 file changed, 2 insertions(+) > > > > > > diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c > > > index 429e5a36c08a9..d38a693b48e03 100644 > > > --- a/drivers/cpufreq/acpi-cpufreq.c > > > +++ b/drivers/cpufreq/acpi-cpufreq.c > > > @@ -247,6 +247,7 @@ static u32 cpu_freq_read_intel(struct acpi_pct_register *not_used) > > > u32 val, dummy; > > > > > > rdmsr(MSR_IA32_PERF_CTL, val, dummy); > > > + dummy &= dummy; /* Silence set but not used warning */ > > > return val; > > > } > > > > > > @@ -264,6 +265,7 @@ static u32 cpu_freq_read_amd(struct acpi_pct_register *not_used) > > > u32 val, dummy; > > > > > > rdmsr(MSR_AMD_PERF_CTL, val, dummy); > > > + dummy &= dummy; /* Silence set but not used warning */ > > > return val; > > > } > > > > > > > _______________________________________________ > > linux-arm-kernel mailing list > > linux-arm-kernel@lists.infradead.org > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > >
diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c index 429e5a36c08a9..d38a693b48e03 100644 --- a/drivers/cpufreq/acpi-cpufreq.c +++ b/drivers/cpufreq/acpi-cpufreq.c @@ -247,6 +247,7 @@ static u32 cpu_freq_read_intel(struct acpi_pct_register *not_used) u32 val, dummy; rdmsr(MSR_IA32_PERF_CTL, val, dummy); + dummy &= dummy; /* Silence set but not used warning */ return val; } @@ -264,6 +265,7 @@ static u32 cpu_freq_read_amd(struct acpi_pct_register *not_used) u32 val, dummy; rdmsr(MSR_AMD_PERF_CTL, val, dummy); + dummy &= dummy; /* Silence set but not used warning */ return val; }
If we fail to use a variable, even a 'dummy' one, then the compiler complains that it is set but not used. We know this is fine, so we set it to its own value here. Fixes the following W=1 kernel build warning(s): drivers/cpufreq/acpi-cpufreq.c: In function ‘cpu_freq_read_intel’: drivers/cpufreq/acpi-cpufreq.c:247:11: warning: variable ‘dummy’ set but not used [-Wunused-but-set-variable] drivers/cpufreq/acpi-cpufreq.c: In function ‘cpu_freq_read_amd’: drivers/cpufreq/acpi-cpufreq.c:265:11: warning: variable ‘dummy’ set but not used [-Wunused-but-set-variable] Cc: Andy Grover <andrew.grover@intel.com> Cc: Paul Diefenbaugh <paul.s.diefenbaugh@intel.com> Cc: Dominik Brodowski <linux@brodo.de> Cc: Denis Sadykov <denis.m.sadykov@intel.com> Signed-off-by: Lee Jones <lee.jones@linaro.org> --- drivers/cpufreq/acpi-cpufreq.c | 2 ++ 1 file changed, 2 insertions(+)