[PATCH v1] x86: Fix incorrect scope of setting `shared_per_thread`

[PATCH v1] x86: Fix incorrect scope of setting `shared_per_thread`

[Noah Goldstein]

The:

```
    if (shared_per_thread > 0 && threads > 0)
      shared_per_thread /= threads;
```

Code was accidentally moved to inside the else scope.  This doesn't
match how it was previously (before af992e7abd).

This patch fixes that by putting the division after the `else` block.
---
 sysdeps/x86/dl-cacheinfo.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/sysdeps/x86/dl-cacheinfo.h b/sysdeps/x86/dl-cacheinfo.h
index 285773039f..88316a7818 100644
--- a/sysdeps/x86/dl-cacheinfo.h
+++ b/sysdeps/x86/dl-cacheinfo.h
@@ -770,11 +770,10 @@ get_common_cache_info (long int *shared_ptr, long int * shared_per_thread_ptr, u
 	     level.  */
 	  threads = ((cpu_features->features[CPUID_INDEX_1].cpuid.ebx >> 16)
 		     & 0xff);
-
+        }
 	  /* Get per-thread size of highest level cache.  */
 	  if (shared_per_thread > 0 && threads > 0)
 	    shared_per_thread /= threads;
-	}
     }
 
   /* Account for non-inclusive L2 and L3 caches.  */
-- 
2.34.1

Re: [PATCH v1] x86: Fix incorrect scope of setting `shared_per_thread`

[H.J. Lu]

On Thu, Aug 10, 2023 at 5:31 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> The:
>
> ```
>     if (shared_per_thread > 0 && threads > 0)
>       shared_per_thread /= threads;
> ```
>
> Code was accidentally moved to inside the else scope.  This doesn't
> match how it was previously (before af992e7abd).
>
> This patch fixes that by putting the division after the `else` block.

Since it is a regression, we should open a bug and backport this
fix.

> ---
>  sysdeps/x86/dl-cacheinfo.h | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/sysdeps/x86/dl-cacheinfo.h b/sysdeps/x86/dl-cacheinfo.h
> index 285773039f..88316a7818 100644
> --- a/sysdeps/x86/dl-cacheinfo.h
> +++ b/sysdeps/x86/dl-cacheinfo.h
> @@ -770,11 +770,10 @@ get_common_cache_info (long int *shared_ptr, long int * shared_per_thread_ptr, u
>              level.  */
>           threads = ((cpu_features->features[CPUID_INDEX_1].cpuid.ebx >> 16)
>                      & 0xff);
> -
> +        }
>           /* Get per-thread size of highest level cache.  */
>           if (shared_per_thread > 0 && threads > 0)
>             shared_per_thread /= threads;
> -       }
>      }
>
>    /* Account for non-inclusive L2 and L3 caches.  */
> --
> 2.34.1
>


-- 
H.J.

Re: [PATCH v1] x86: Fix incorrect scope of setting `shared_per_thread`

[Noah Goldstein]

On Thu, Aug 10, 2023 at 8:38 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Thu, Aug 10, 2023 at 5:31 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
> >
> > The:
> >
> > ```
> >     if (shared_per_thread > 0 && threads > 0)
> >       shared_per_thread /= threads;
> > ```
> >
> > Code was accidentally moved to inside the else scope.  This doesn't
> > match how it was previously (before af992e7abd).
> >
> > This patch fixes that by putting the division after the `else` block.
>
> Since it is a regression, we should open a bug and backport this
> fix.

Done: See https://sourceware.org/bugzilla/show_bug.cgi?id=30745
FYI: I changed title to include BZ number so doesn't reply in chain.
>
> > ---
> >  sysdeps/x86/dl-cacheinfo.h | 3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/sysdeps/x86/dl-cacheinfo.h b/sysdeps/x86/dl-cacheinfo.h
> > index 285773039f..88316a7818 100644
> > --- a/sysdeps/x86/dl-cacheinfo.h
> > +++ b/sysdeps/x86/dl-cacheinfo.h
> > @@ -770,11 +770,10 @@ get_common_cache_info (long int *shared_ptr, long int * shared_per_thread_ptr, u
> >              level.  */
> >           threads = ((cpu_features->features[CPUID_INDEX_1].cpuid.ebx >> 16)
> >                      & 0xff);
> > -
> > +        }
> >           /* Get per-thread size of highest level cache.  */
> >           if (shared_per_thread > 0 && threads > 0)
> >             shared_per_thread /= threads;
> > -       }
> >      }
> >
> >    /* Account for non-inclusive L2 and L3 caches.  */
> > --
> > 2.34.1
> >
>
>
> --
> H.J.

[PATCH v2] x86: Fix incorrect scope of setting `shared_per_thread` [BZ# 30745]

[Noah Goldstein]

The:

```
    if (shared_per_thread > 0 && threads > 0)
      shared_per_thread /= threads;
```

Code was accidentally moved to inside the else scope.  This doesn't
match how it was previously (before af992e7abd).

This patch fixes that by putting the division after the `else` block.
---
 sysdeps/x86/dl-cacheinfo.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/sysdeps/x86/dl-cacheinfo.h b/sysdeps/x86/dl-cacheinfo.h
index 285773039f..88316a7818 100644
--- a/sysdeps/x86/dl-cacheinfo.h
+++ b/sysdeps/x86/dl-cacheinfo.h
@@ -770,11 +770,10 @@ get_common_cache_info (long int *shared_ptr, long int * shared_per_thread_ptr, u
 	     level.  */
 	  threads = ((cpu_features->features[CPUID_INDEX_1].cpuid.ebx >> 16)
 		     & 0xff);
-
+        }
 	  /* Get per-thread size of highest level cache.  */
 	  if (shared_per_thread > 0 && threads > 0)
 	    shared_per_thread /= threads;
-	}
     }
 
   /* Account for non-inclusive L2 and L3 caches.  */
-- 
2.34.1

Re: [PATCH v2] x86: Fix incorrect scope of setting `shared_per_thread` [BZ# 30745]

[Andreas Schwab]

On Aug 10 2023, Noah Goldstein via Libc-alpha wrote:

> diff --git a/sysdeps/x86/dl-cacheinfo.h b/sysdeps/x86/dl-cacheinfo.h
> index 285773039f..88316a7818 100644
> --- a/sysdeps/x86/dl-cacheinfo.h
> +++ b/sysdeps/x86/dl-cacheinfo.h
> @@ -770,11 +770,10 @@ get_common_cache_info (long int *shared_ptr, long int * shared_per_thread_ptr, u
>  	     level.  */
>  	  threads = ((cpu_features->features[CPUID_INDEX_1].cpuid.ebx >> 16)
>  		     & 0xff);
> -
> +        }
>  	  /* Get per-thread size of highest level cache.  */
>  	  if (shared_per_thread > 0 && threads > 0)
>  	    shared_per_thread /= threads;
> -	}

Please fix the indentation.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
"And now for something completely different."

Re: [PATCH v2] x86: Fix incorrect scope of setting `shared_per_thread` [BZ# 30745]

[Noah Goldstein]

On Fri, Aug 11, 2023 at 2:46 AM Andreas Schwab <schwab@linux-m68k.org> wrote:
>
> On Aug 10 2023, Noah Goldstein via Libc-alpha wrote:
>
> > diff --git a/sysdeps/x86/dl-cacheinfo.h b/sysdeps/x86/dl-cacheinfo.h
> > index 285773039f..88316a7818 100644
> > --- a/sysdeps/x86/dl-cacheinfo.h
> > +++ b/sysdeps/x86/dl-cacheinfo.h
> > @@ -770,11 +770,10 @@ get_common_cache_info (long int *shared_ptr, long int * shared_per_thread_ptr, u
> >            level.  */
> >         threads = ((cpu_features->features[CPUID_INDEX_1].cpuid.ebx >> 16)
> >                    & 0xff);
> > -
> > +        }
> >         /* Get per-thread size of highest level cache.  */
> >         if (shared_per_thread > 0 && threads > 0)
> >           shared_per_thread /= threads;
> > -     }
>
> Please fix the indentation.
>

Done.
> --
> Andreas Schwab, schwab@linux-m68k.org
> GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
> "And now for something completely different."

[PATCH v3] x86: Fix incorrect scope of setting `shared_per_thread` [BZ# 30745]

[Noah Goldstein]

The:

```
    if (shared_per_thread > 0 && threads > 0)
      shared_per_thread /= threads;
```

Code was accidentally moved to inside the else scope.  This doesn't
match how it was previously (before af992e7abd).

This patch fixes that by putting the division after the `else` block.
---
 sysdeps/x86/dl-cacheinfo.h | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/sysdeps/x86/dl-cacheinfo.h b/sysdeps/x86/dl-cacheinfo.h
index 285773039f..5ddb35c9d9 100644
--- a/sysdeps/x86/dl-cacheinfo.h
+++ b/sysdeps/x86/dl-cacheinfo.h
@@ -770,11 +770,10 @@ get_common_cache_info (long int *shared_ptr, long int * shared_per_thread_ptr, u
 	     level.  */
 	  threads = ((cpu_features->features[CPUID_INDEX_1].cpuid.ebx >> 16)
 		     & 0xff);
-
-	  /* Get per-thread size of highest level cache.  */
-	  if (shared_per_thread > 0 && threads > 0)
-	    shared_per_thread /= threads;
 	}
+      /* Get per-thread size of highest level cache.  */
+      if (shared_per_thread > 0 && threads > 0)
+	shared_per_thread /= threads;
     }
 
   /* Account for non-inclusive L2 and L3 caches.  */
-- 
2.34.1

Re: [PATCH v3] x86: Fix incorrect scope of setting `shared_per_thread` [BZ# 30745]

[H.J. Lu]

On Fri, Aug 11, 2023 at 10:29 AM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> The:
>
> ```
>     if (shared_per_thread > 0 && threads > 0)
>       shared_per_thread /= threads;
> ```
>
> Code was accidentally moved to inside the else scope.  This doesn't
> match how it was previously (before af992e7abd).
>
> This patch fixes that by putting the division after the `else` block.
> ---
>  sysdeps/x86/dl-cacheinfo.h | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/sysdeps/x86/dl-cacheinfo.h b/sysdeps/x86/dl-cacheinfo.h
> index 285773039f..5ddb35c9d9 100644
> --- a/sysdeps/x86/dl-cacheinfo.h
> +++ b/sysdeps/x86/dl-cacheinfo.h
> @@ -770,11 +770,10 @@ get_common_cache_info (long int *shared_ptr, long int * shared_per_thread_ptr, u
>              level.  */
>           threads = ((cpu_features->features[CPUID_INDEX_1].cpuid.ebx >> 16)
>                      & 0xff);
> -
> -         /* Get per-thread size of highest level cache.  */
> -         if (shared_per_thread > 0 && threads > 0)
> -           shared_per_thread /= threads;
>         }
> +      /* Get per-thread size of highest level cache.  */
> +      if (shared_per_thread > 0 && threads > 0)
> +       shared_per_thread /= threads;
>      }
>
>    /* Account for non-inclusive L2 and L3 caches.  */
> --
> 2.34.1
>

LGTM.

Thanks.

-- 
H.J.

Re: [PATCH v3] x86: Fix incorrect scope of setting `shared_per_thread` [BZ# 30745]

[Carlos O'Donell]

On 8/11/23 13:31, H.J. Lu via Libc-alpha wrote:
> On Fri, Aug 11, 2023 at 10:29 AM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>>
>> The:
>>
>> ```
>>     if (shared_per_thread > 0 && threads > 0)
>>       shared_per_thread /= threads;
>> ```
>>
>> Code was accidentally moved to inside the else scope.  This doesn't
>> match how it was previously (before af992e7abd).
>>
>> This patch fixes that by putting the division after the `else` block.
>> ---
>>  sysdeps/x86/dl-cacheinfo.h | 7 +++----
>>  1 file changed, 3 insertions(+), 4 deletions(-)
>>
>> diff --git a/sysdeps/x86/dl-cacheinfo.h b/sysdeps/x86/dl-cacheinfo.h
>> index 285773039f..5ddb35c9d9 100644
>> --- a/sysdeps/x86/dl-cacheinfo.h
>> +++ b/sysdeps/x86/dl-cacheinfo.h
>> @@ -770,11 +770,10 @@ get_common_cache_info (long int *shared_ptr, long int * shared_per_thread_ptr, u
>>              level.  */
>>           threads = ((cpu_features->features[CPUID_INDEX_1].cpuid.ebx >> 16)
>>                      & 0xff);
>> -
>> -         /* Get per-thread size of highest level cache.  */
>> -         if (shared_per_thread > 0 && threads > 0)
>> -           shared_per_thread /= threads;
>>         }
>> +      /* Get per-thread size of highest level cache.  */
>> +      if (shared_per_thread > 0 && threads > 0)
>> +       shared_per_thread /= threads;
>>      }
>>
>>    /* Account for non-inclusive L2 and L3 caches.  */
>> --
>> 2.34.1
>>
> 
> LGTM.
> 
> Thanks.
 
This impacts CentOS 8 Stream and CentOS 9 Stream, which have backports of this
sequence of changes. I'm testing the changes right now.

-- 
Cheers,
Carlos.

Re: [PATCH v3] x86: Fix incorrect scope of setting `shared_per_thread` [BZ# 30745]

[Carlos O'Donell]

On 8/11/23 13:29, Noah Goldstein via Libc-alpha wrote:
> The:
> 
> ```
>     if (shared_per_thread > 0 && threads > 0)
>       shared_per_thread /= threads;
> ```
> 
> Code was accidentally moved to inside the else scope.  This doesn't
> match how it was previously (before af992e7abd).
> 
> This patch fixes that by putting the division after the `else` block.

LGTM. Tested on i686 and x86_64.

I also backported this to c8s and c9s and re-tested and everything
passes there without regression on i686, x86_64.

I'm going to do some additional testing, but that's enough for me
to see this get pushed. Thank you!

Tested-by: Carlos O'Donell <carlos@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>

> ---
>  sysdeps/x86/dl-cacheinfo.h | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/sysdeps/x86/dl-cacheinfo.h b/sysdeps/x86/dl-cacheinfo.h
> index 285773039f..5ddb35c9d9 100644
> --- a/sysdeps/x86/dl-cacheinfo.h
> +++ b/sysdeps/x86/dl-cacheinfo.h
> @@ -770,11 +770,10 @@ get_common_cache_info (long int *shared_ptr, long int * shared_per_thread_ptr, u
>  	     level.  */
>  	  threads = ((cpu_features->features[CPUID_INDEX_1].cpuid.ebx >> 16)
>  		     & 0xff);
> -
> -	  /* Get per-thread size of highest level cache.  */
> -	  if (shared_per_thread > 0 && threads > 0)
> -	    shared_per_thread /= threads;
>  	}
> +      /* Get per-thread size of highest level cache.  */
> +      if (shared_per_thread > 0 && threads > 0)
> +	shared_per_thread /= threads;
>      }
>  
>    /* Account for non-inclusive L2 and L3 caches.  */

-- 
Cheers,
Carlos.

Re: [PATCH v3] x86: Fix incorrect scope of setting `shared_per_thread` [BZ# 30745]

[Noah Goldstein]

On Fri, Aug 11, 2023 at 2:38 PM Carlos O'Donell <carlos@redhat.com> wrote:
>
> On 8/11/23 13:29, Noah Goldstein via Libc-alpha wrote:
> > The:
> >
> > ```
> >     if (shared_per_thread > 0 && threads > 0)
> >       shared_per_thread /= threads;
> > ```
> >
> > Code was accidentally moved to inside the else scope.  This doesn't
> > match how it was previously (before af992e7abd).
> >
> > This patch fixes that by putting the division after the `else` block.
>
> LGTM. Tested on i686 and x86_64.
>
> I also backported this to c8s and c9s and re-tested and everything
> passes there without regression on i686, x86_64.
>
> I'm going to do some additional testing, but that's enough for me
> to see this get pushed. Thank you!
>
> Tested-by: Carlos O'Donell <carlos@redhat.com>
> Reviewed-by: Carlos O'Donell <carlos@redhat.com>
>
> > ---
> >  sysdeps/x86/dl-cacheinfo.h | 7 +++----
> >  1 file changed, 3 insertions(+), 4 deletions(-)
> >
> > diff --git a/sysdeps/x86/dl-cacheinfo.h b/sysdeps/x86/dl-cacheinfo.h
> > index 285773039f..5ddb35c9d9 100644
> > --- a/sysdeps/x86/dl-cacheinfo.h
> > +++ b/sysdeps/x86/dl-cacheinfo.h
> > @@ -770,11 +770,10 @@ get_common_cache_info (long int *shared_ptr, long int * shared_per_thread_ptr, u
> >            level.  */
> >         threads = ((cpu_features->features[CPUID_INDEX_1].cpuid.ebx >> 16)
> >                    & 0xff);
> > -
> > -       /* Get per-thread size of highest level cache.  */
> > -       if (shared_per_thread > 0 && threads > 0)
> > -         shared_per_thread /= threads;
> >       }
> > +      /* Get per-thread size of highest level cache.  */
> > +      if (shared_per_thread > 0 && threads > 0)
> > +     shared_per_thread /= threads;
> >      }
> >
> >    /* Account for non-inclusive L2 and L3 caches.  */
>
> --
> Cheers,
> Carlos.
>

Any objections to me backporting this to 2.38 release branch?