[PATCH] x86: mmiotrace: Use cpumask_available for cpumask_var_t variables

[PATCH] x86: mmiotrace: Use cpumask_available for cpumask_var_t variables

[Nathan Chancellor]

When building with Clang + -Wtautological-compare and
CONFIG_CPUMASK_OFFSTACK unset:

arch/x86/mm/mmio-mod.c:375:6: warning: comparison of array 'downed_cpus'
equal to a null pointer is always false [-Wtautological-pointer-compare]
        if (downed_cpus == NULL &&
            ^~~~~~~~~~~    ~~~~
arch/x86/mm/mmio-mod.c:405:6: warning: comparison of array 'downed_cpus'
equal to a null pointer is always false [-Wtautological-pointer-compare]
        if (downed_cpus == NULL || cpumask_weight(downed_cpus) == 0)
            ^~~~~~~~~~~    ~~~~
2 warnings generated.

Commit f7e30f01a9e2 ("cpumask: Add helper cpumask_available()") added
cpumask_available to fix warnings of this nature. Use that here so that
clang does not warn regardless of CONFIG_CPUMASK_OFFSTACK's value.

Link: https://github.com/ClangBuiltLinux/linux/issues/982
Reported-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
---
 arch/x86/mm/mmio-mod.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/mmio-mod.c b/arch/x86/mm/mmio-mod.c
index 109325d77b3e..43fd19b3f118 100644
--- a/arch/x86/mm/mmio-mod.c
+++ b/arch/x86/mm/mmio-mod.c
@@ -372,7 +372,7 @@ static void enter_uniprocessor(void)
 	int cpu;
 	int err;
 
-	if (downed_cpus == NULL &&
+	if (!cpumask_available(downed_cpus) &&
 	    !alloc_cpumask_var(&downed_cpus, GFP_KERNEL)) {
 		pr_notice("Failed to allocate mask\n");
 		goto out;
@@ -402,7 +402,7 @@ static void leave_uniprocessor(void)
 	int cpu;
 	int err;
 
-	if (downed_cpus == NULL || cpumask_weight(downed_cpus) == 0)
+	if (!cpumask_available(downed_cpus) || cpumask_weight(downed_cpus) == 0)
 		return;
 	pr_notice("Re-enabling CPUs...\n");
 	for_each_cpu(cpu, downed_cpus) {

base-commit: ae46d2aa6a7fbe8ca0946f24b061b6ccdc6c3f25
-- 
2.26.0

Re: [PATCH] x86: mmiotrace: Use cpumask_available for cpumask_var_t variables

[Sedat Dilek]

On Wed, Apr 8, 2020 at 10:53 PM Nathan Chancellor
<natechancellor@gmail.com> wrote:
>
> When building with Clang + -Wtautological-compare and
> CONFIG_CPUMASK_OFFSTACK unset:
>

Hi Nathan,

thanks for the quick patch.

I can confirm I have no CONFIG_CPUMASK_OFFSTACK set.

Regards,
- Sedat -


> arch/x86/mm/mmio-mod.c:375:6: warning: comparison of array 'downed_cpus'
> equal to a null pointer is always false [-Wtautological-pointer-compare]
>         if (downed_cpus == NULL &&
>             ^~~~~~~~~~~    ~~~~
> arch/x86/mm/mmio-mod.c:405:6: warning: comparison of array 'downed_cpus'
> equal to a null pointer is always false [-Wtautological-pointer-compare]
>         if (downed_cpus == NULL || cpumask_weight(downed_cpus) == 0)
>             ^~~~~~~~~~~    ~~~~
> 2 warnings generated.
>
> Commit f7e30f01a9e2 ("cpumask: Add helper cpumask_available()") added
> cpumask_available to fix warnings of this nature. Use that here so that
> clang does not warn regardless of CONFIG_CPUMASK_OFFSTACK's value.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/982
> Reported-by: Sedat Dilek <sedat.dilek@gmail.com>
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> ---
>  arch/x86/mm/mmio-mod.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/mm/mmio-mod.c b/arch/x86/mm/mmio-mod.c
> index 109325d77b3e..43fd19b3f118 100644
> --- a/arch/x86/mm/mmio-mod.c
> +++ b/arch/x86/mm/mmio-mod.c
> @@ -372,7 +372,7 @@ static void enter_uniprocessor(void)
>         int cpu;
>         int err;
>
> -       if (downed_cpus == NULL &&
> +       if (!cpumask_available(downed_cpus) &&
>             !alloc_cpumask_var(&downed_cpus, GFP_KERNEL)) {
>                 pr_notice("Failed to allocate mask\n");
>                 goto out;
> @@ -402,7 +402,7 @@ static void leave_uniprocessor(void)
>         int cpu;
>         int err;
>
> -       if (downed_cpus == NULL || cpumask_weight(downed_cpus) == 0)
> +       if (!cpumask_available(downed_cpus) || cpumask_weight(downed_cpus) == 0)
>                 return;
>         pr_notice("Re-enabling CPUs...\n");
>         for_each_cpu(cpu, downed_cpus) {
>
> base-commit: ae46d2aa6a7fbe8ca0946f24b061b6ccdc6c3f25
> --
> 2.26.0
>

Re: [PATCH] x86: mmiotrace: Use cpumask_available for cpumask_var_t variables

[Sedat Dilek]

On Wed, Apr 8, 2020 at 11:12 PM Sedat Dilek <sedat.dilek@gmail.com> wrote:
>
> On Wed, Apr 8, 2020 at 10:53 PM Nathan Chancellor
> <natechancellor@gmail.com> wrote:
> >
> > When building with Clang + -Wtautological-compare and
> > CONFIG_CPUMASK_OFFSTACK unset:
> >
>
> Hi Nathan,
>
> thanks for the quick patch.
>
> I can confirm I have no CONFIG_CPUMASK_OFFSTACK set.
>

Feel free to add appropriate credits:

   Tested-by: Sedat Dilek <sedat.dilek@gmail.com>

Regards,
- Sedat -

>
> > arch/x86/mm/mmio-mod.c:375:6: warning: comparison of array 'downed_cpus'
> > equal to a null pointer is always false [-Wtautological-pointer-compare]
> >         if (downed_cpus == NULL &&
> >             ^~~~~~~~~~~    ~~~~
> > arch/x86/mm/mmio-mod.c:405:6: warning: comparison of array 'downed_cpus'
> > equal to a null pointer is always false [-Wtautological-pointer-compare]
> >         if (downed_cpus == NULL || cpumask_weight(downed_cpus) == 0)
> >             ^~~~~~~~~~~    ~~~~
> > 2 warnings generated.
> >
> > Commit f7e30f01a9e2 ("cpumask: Add helper cpumask_available()") added
> > cpumask_available to fix warnings of this nature. Use that here so that
> > clang does not warn regardless of CONFIG_CPUMASK_OFFSTACK's value.
> >
> > Link: https://github.com/ClangBuiltLinux/linux/issues/982
> > Reported-by: Sedat Dilek <sedat.dilek@gmail.com>
> > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> > ---
> >  arch/x86/mm/mmio-mod.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/mm/mmio-mod.c b/arch/x86/mm/mmio-mod.c
> > index 109325d77b3e..43fd19b3f118 100644
> > --- a/arch/x86/mm/mmio-mod.c
> > +++ b/arch/x86/mm/mmio-mod.c
> > @@ -372,7 +372,7 @@ static void enter_uniprocessor(void)
> >         int cpu;
> >         int err;
> >
> > -       if (downed_cpus == NULL &&
> > +       if (!cpumask_available(downed_cpus) &&
> >             !alloc_cpumask_var(&downed_cpus, GFP_KERNEL)) {
> >                 pr_notice("Failed to allocate mask\n");
> >                 goto out;
> > @@ -402,7 +402,7 @@ static void leave_uniprocessor(void)
> >         int cpu;
> >         int err;
> >
> > -       if (downed_cpus == NULL || cpumask_weight(downed_cpus) == 0)
> > +       if (!cpumask_available(downed_cpus) || cpumask_weight(downed_cpus) == 0)
> >                 return;
> >         pr_notice("Re-enabling CPUs...\n");
> >         for_each_cpu(cpu, downed_cpus) {
> >
> > base-commit: ae46d2aa6a7fbe8ca0946f24b061b6ccdc6c3f25
> > --
> > 2.26.0
> >

Re: [PATCH] x86: mmiotrace: Use cpumask_available for cpumask_var_t variables

[Sedat Dilek]

On Wed, Apr 8, 2020 at 11:36 PM Sedat Dilek <sedat.dilek@gmail.com> wrote:

[ ... ]

> Feel free to add appropriate credits:
>
>    Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
>

Re-tested with Linux v5.7-rc1 which shows this warning - with GCC v9.3
and LLVM/Clang v10.0.0 (and snapshot/pre-release of v10.0.1) on
Debian/testing AMD64.

- Sedat -

Re: [PATCH] x86: mmiotrace: Use cpumask_available for cpumask_var_t variables

[Steven Rostedt]

On Wed,  8 Apr 2020 13:53:23 -0700
Nathan Chancellor <natechancellor@gmail.com> wrote:

> When building with Clang + -Wtautological-compare and
> CONFIG_CPUMASK_OFFSTACK unset:
> 
> arch/x86/mm/mmio-mod.c:375:6: warning: comparison of array 'downed_cpus'
> equal to a null pointer is always false [-Wtautological-pointer-compare]
>         if (downed_cpus == NULL &&
>             ^~~~~~~~~~~    ~~~~
> arch/x86/mm/mmio-mod.c:405:6: warning: comparison of array 'downed_cpus'
> equal to a null pointer is always false [-Wtautological-pointer-compare]
>         if (downed_cpus == NULL || cpumask_weight(downed_cpus) == 0)
>             ^~~~~~~~~~~    ~~~~
> 2 warnings generated.
> 
> Commit f7e30f01a9e2 ("cpumask: Add helper cpumask_available()") added
> cpumask_available to fix warnings of this nature. Use that here so that
> clang does not warn regardless of CONFIG_CPUMASK_OFFSTACK's value.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/982
> Reported-by: Sedat Dilek <sedat.dilek@gmail.com>
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> ---
> 

Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

-- Steve

Re: [PATCH] x86: mmiotrace: Use cpumask_available for cpumask_var_t variables

[Nathan Chancellor]

On Wed, Apr 08, 2020 at 01:53:23PM -0700, Nathan Chancellor wrote:
> When building with Clang + -Wtautological-compare and
> CONFIG_CPUMASK_OFFSTACK unset:
> 
> arch/x86/mm/mmio-mod.c:375:6: warning: comparison of array 'downed_cpus'
> equal to a null pointer is always false [-Wtautological-pointer-compare]
>         if (downed_cpus == NULL &&
>             ^~~~~~~~~~~    ~~~~
> arch/x86/mm/mmio-mod.c:405:6: warning: comparison of array 'downed_cpus'
> equal to a null pointer is always false [-Wtautological-pointer-compare]
>         if (downed_cpus == NULL || cpumask_weight(downed_cpus) == 0)
>             ^~~~~~~~~~~    ~~~~
> 2 warnings generated.
> 
> Commit f7e30f01a9e2 ("cpumask: Add helper cpumask_available()") added
> cpumask_available to fix warnings of this nature. Use that here so that
> clang does not warn regardless of CONFIG_CPUMASK_OFFSTACK's value.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/982
> Reported-by: Sedat Dilek <sedat.dilek@gmail.com>
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> ---
>  arch/x86/mm/mmio-mod.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/mm/mmio-mod.c b/arch/x86/mm/mmio-mod.c
> index 109325d77b3e..43fd19b3f118 100644
> --- a/arch/x86/mm/mmio-mod.c
> +++ b/arch/x86/mm/mmio-mod.c
> @@ -372,7 +372,7 @@ static void enter_uniprocessor(void)
>  	int cpu;
>  	int err;
>  
> -	if (downed_cpus == NULL &&
> +	if (!cpumask_available(downed_cpus) &&
>  	    !alloc_cpumask_var(&downed_cpus, GFP_KERNEL)) {
>  		pr_notice("Failed to allocate mask\n");
>  		goto out;
> @@ -402,7 +402,7 @@ static void leave_uniprocessor(void)
>  	int cpu;
>  	int err;
>  
> -	if (downed_cpus == NULL || cpumask_weight(downed_cpus) == 0)
> +	if (!cpumask_available(downed_cpus) || cpumask_weight(downed_cpus) == 0)
>  		return;
>  	pr_notice("Re-enabling CPUs...\n");
>  	for_each_cpu(cpu, downed_cpus) {
> 
> base-commit: ae46d2aa6a7fbe8ca0946f24b061b6ccdc6c3f25
> -- 
> 2.26.0
> 

Gentle ping for acceptance, I am not sure who should take this.

Cheers,
Nathan

Re: [PATCH] x86: mmiotrace: Use cpumask_available for cpumask_var_t variables

[Nick Desaulniers]

On Mon, May 18, 2020 at 2:31 AM Nathan Chancellor
<natechancellor@gmail.com> wrote:
>
> On Wed, Apr 08, 2020 at 01:53:23PM -0700, Nathan Chancellor wrote:
> > When building with Clang + -Wtautological-compare and
> > CONFIG_CPUMASK_OFFSTACK unset:
> >
> > arch/x86/mm/mmio-mod.c:375:6: warning: comparison of array 'downed_cpus'
> > equal to a null pointer is always false [-Wtautological-pointer-compare]
> >         if (downed_cpus == NULL &&
> >             ^~~~~~~~~~~    ~~~~
> > arch/x86/mm/mmio-mod.c:405:6: warning: comparison of array 'downed_cpus'
> > equal to a null pointer is always false [-Wtautological-pointer-compare]
> >         if (downed_cpus == NULL || cpumask_weight(downed_cpus) == 0)
> >             ^~~~~~~~~~~    ~~~~
> > 2 warnings generated.
> >
> > Commit f7e30f01a9e2 ("cpumask: Add helper cpumask_available()") added
> > cpumask_available to fix warnings of this nature. Use that here so that
> > clang does not warn regardless of CONFIG_CPUMASK_OFFSTACK's value.
> >
> > Link: https://github.com/ClangBuiltLinux/linux/issues/982
> > Reported-by: Sedat Dilek <sedat.dilek@gmail.com>
> > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>

Thanks for the patch, sorry I'm falling behind on code review!
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

> > ---
> >  arch/x86/mm/mmio-mod.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/mm/mmio-mod.c b/arch/x86/mm/mmio-mod.c
> > index 109325d77b3e..43fd19b3f118 100644
> > --- a/arch/x86/mm/mmio-mod.c
> > +++ b/arch/x86/mm/mmio-mod.c
> > @@ -372,7 +372,7 @@ static void enter_uniprocessor(void)
> >       int cpu;
> >       int err;
> >
> > -     if (downed_cpus == NULL &&
> > +     if (!cpumask_available(downed_cpus) &&
> >           !alloc_cpumask_var(&downed_cpus, GFP_KERNEL)) {
> >               pr_notice("Failed to allocate mask\n");
> >               goto out;
> > @@ -402,7 +402,7 @@ static void leave_uniprocessor(void)
> >       int cpu;
> >       int err;
> >
> > -     if (downed_cpus == NULL || cpumask_weight(downed_cpus) == 0)
> > +     if (!cpumask_available(downed_cpus) || cpumask_weight(downed_cpus) == 0)
> >               return;
> >       pr_notice("Re-enabling CPUs...\n");
> >       for_each_cpu(cpu, downed_cpus) {
> >
> > base-commit: ae46d2aa6a7fbe8ca0946f24b061b6ccdc6c3f25
> > --
> > 2.26.0
> >
>
> Gentle ping for acceptance, I am not sure who should take this.

Looks like Steven or Ingo are the listed maintainers for MMIOTRACE?

-- 
Thanks,
~Nick Desaulniers

Re: [PATCH] x86: mmiotrace: Use cpumask_available for cpumask_var_t variables

[Steven Rostedt]

On Mon, 18 May 2020 11:52:47 -0700
Nick Desaulniers <ndesaulniers@google.com> wrote:

> On Mon, May 18, 2020 at 2:31 AM Nathan Chancellor
> <natechancellor@gmail.com> wrote:
> >
> > On Wed, Apr 08, 2020 at 01:53:23PM -0700, Nathan Chancellor wrote:  
> > > When building with Clang + -Wtautological-compare and
> > > CONFIG_CPUMASK_OFFSTACK unset:
> > >
> > > arch/x86/mm/mmio-mod.c:375:6: warning: comparison of array 'downed_cpus'
> > > equal to a null pointer is always false [-Wtautological-pointer-compare]
> > >         if (downed_cpus == NULL &&
> > >             ^~~~~~~~~~~    ~~~~
> > > arch/x86/mm/mmio-mod.c:405:6: warning: comparison of array 'downed_cpus'
> > > equal to a null pointer is always false [-Wtautological-pointer-compare]
> > >         if (downed_cpus == NULL || cpumask_weight(downed_cpus) == 0)
> > >             ^~~~~~~~~~~    ~~~~
> > > 2 warnings generated.
> > >
> > > Commit f7e30f01a9e2 ("cpumask: Add helper cpumask_available()") added
> > > cpumask_available to fix warnings of this nature. Use that here so that
> > > clang does not warn regardless of CONFIG_CPUMASK_OFFSTACK's value.
> > >
> > > Link: https://github.com/ClangBuiltLinux/linux/issues/982
> > > Reported-by: Sedat Dilek <sedat.dilek@gmail.com>
> > > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>  
> 
> Thanks for the patch, sorry I'm falling behind on code review!
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

Linus sent me a issue about this failure privately as well, and had two
solutions for it (one being identical to this one, and I shared that with
him, and another one he thought would be better, but had some issues).

Linus,

Are you OK with this patch?

-- Steve


> 
> > > ---
> > >  arch/x86/mm/mmio-mod.c | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/arch/x86/mm/mmio-mod.c b/arch/x86/mm/mmio-mod.c
> > > index 109325d77b3e..43fd19b3f118 100644
> > > --- a/arch/x86/mm/mmio-mod.c
> > > +++ b/arch/x86/mm/mmio-mod.c
> > > @@ -372,7 +372,7 @@ static void enter_uniprocessor(void)
> > >       int cpu;
> > >       int err;
> > >
> > > -     if (downed_cpus == NULL &&
> > > +     if (!cpumask_available(downed_cpus) &&
> > >           !alloc_cpumask_var(&downed_cpus, GFP_KERNEL)) {
> > >               pr_notice("Failed to allocate mask\n");
> > >               goto out;
> > > @@ -402,7 +402,7 @@ static void leave_uniprocessor(void)
> > >       int cpu;
> > >       int err;
> > >
> > > -     if (downed_cpus == NULL || cpumask_weight(downed_cpus) == 0)
> > > +     if (!cpumask_available(downed_cpus) || cpumask_weight(downed_cpus) == 0)
> > >               return;
> > >       pr_notice("Re-enabling CPUs...\n");
> > >       for_each_cpu(cpu, downed_cpus) {
> > >
> > > base-commit: ae46d2aa6a7fbe8ca0946f24b061b6ccdc6c3f25
> > > --
> > > 2.26.0
> > >  
> >
> > Gentle ping for acceptance, I am not sure who should take this.  
> 
> Looks like Steven or Ingo are the listed maintainers for MMIOTRACE?
> 

Re: [PATCH] x86: mmiotrace: Use cpumask_available for cpumask_var_t variables

[Linus Torvalds]

On Mon, May 18, 2020 at 3:35 PM Steven Rostedt <rostedt@goodmis.org> wrote:
>
> Linus,
>
> Are you OK with this patch?

Yup, I don't care deeply either way, as long as we can get rid of the warning.

                Linus

[tip: x86/urgent] x86/mmiotrace: Use cpumask_available() for cpumask_var_t variables

[tip-bot2 for Nathan Chancellor]

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     d7110a26e5905ec2fe3fc88bc6a538901accb72b
Gitweb:        https://git.kernel.org/tip/d7110a26e5905ec2fe3fc88bc6a538901accb72b
Author:        Nathan Chancellor <natechancellor@gmail.com>
AuthorDate:    Wed, 08 Apr 2020 13:53:23 -07:00
Committer:     Borislav Petkov <bp@suse.de>
CommitterDate: Tue, 19 May 2020 19:30:28 +02:00

x86/mmiotrace: Use cpumask_available() for cpumask_var_t variables

When building with Clang + -Wtautological-compare and
CONFIG_CPUMASK_OFFSTACK unset:

  arch/x86/mm/mmio-mod.c:375:6: warning: comparison of array 'downed_cpus'
  equal to a null pointer is always false [-Wtautological-pointer-compare]
          if (downed_cpus == NULL &&
              ^~~~~~~~~~~    ~~~~
  arch/x86/mm/mmio-mod.c:405:6: warning: comparison of array 'downed_cpus'
  equal to a null pointer is always false [-Wtautological-pointer-compare]
          if (downed_cpus == NULL || cpumask_weight(downed_cpus) == 0)
              ^~~~~~~~~~~    ~~~~
  2 warnings generated.

Commit

  f7e30f01a9e2 ("cpumask: Add helper cpumask_available()")

added cpumask_available() to fix warnings of this nature. Use that here
so that clang does not warn regardless of CONFIG_CPUMASK_OFFSTACK's
value.

Reported-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Link: https://github.com/ClangBuiltLinux/linux/issues/982
Link: https://lkml.kernel.org/r/20200408205323.44490-1-natechancellor@gmail.com
---
 arch/x86/mm/mmio-mod.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/mmio-mod.c b/arch/x86/mm/mmio-mod.c
index 109325d..43fd19b 100644
--- a/arch/x86/mm/mmio-mod.c
+++ b/arch/x86/mm/mmio-mod.c
@@ -372,7 +372,7 @@ static void enter_uniprocessor(void)
 	int cpu;
 	int err;
 
-	if (downed_cpus == NULL &&
+	if (!cpumask_available(downed_cpus) &&
 	    !alloc_cpumask_var(&downed_cpus, GFP_KERNEL)) {
 		pr_notice("Failed to allocate mask\n");
 		goto out;
@@ -402,7 +402,7 @@ static void leave_uniprocessor(void)
 	int cpu;
 	int err;
 
-	if (downed_cpus == NULL || cpumask_weight(downed_cpus) == 0)
+	if (!cpumask_available(downed_cpus) || cpumask_weight(downed_cpus) == 0)
 		return;
 	pr_notice("Re-enabling CPUs...\n");
 	for_each_cpu(cpu, downed_cpus) {