[PATCH] locking/arch: Move qrwlock.h include after qspinlock.h

[PATCH] locking/arch: Move qrwlock.h include after qspinlock.h

[Waiman Long]

The queued rwlock code has a dependency on the current spinlock
implementation (likely to be qspinlock), but not vice versa. Including
qrwlock.h before qspinlock.h can be problematic when expanding qrwlock
functionality.

If both qspinlock.h and qrwlock.h are to be included, the qrwlock.h
include should always be after qspinlock.h. Update the current set of
asm/spinlock.h files to enforce that.

Signed-off-by: Waiman Long <longman@redhat.com>
---
 arch/arm64/include/asm/spinlock.h  | 2 +-
 arch/mips/include/asm/spinlock.h   | 2 +-
 arch/xtensa/include/asm/spinlock.h | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/spinlock.h b/arch/arm64/include/asm/spinlock.h
index 9083d6992603..0525c0b089ed 100644
--- a/arch/arm64/include/asm/spinlock.h
+++ b/arch/arm64/include/asm/spinlock.h
@@ -5,8 +5,8 @@
 #ifndef __ASM_SPINLOCK_H
 #define __ASM_SPINLOCK_H
 
-#include <asm/qrwlock.h>
 #include <asm/qspinlock.h>
+#include <asm/qrwlock.h>
 
 /* See include/linux/spinlock.h */
 #define smp_mb__after_spinlock()	smp_mb()
diff --git a/arch/mips/include/asm/spinlock.h b/arch/mips/include/asm/spinlock.h
index 8a88eb265516..6ce2117e49f6 100644
--- a/arch/mips/include/asm/spinlock.h
+++ b/arch/mips/include/asm/spinlock.h
@@ -10,7 +10,6 @@
 #define _ASM_SPINLOCK_H
 
 #include <asm/processor.h>
-#include <asm/qrwlock.h>
 
 #include <asm-generic/qspinlock_types.h>
 
@@ -27,5 +26,6 @@ static inline void queued_spin_unlock(struct qspinlock *lock)
 }
 
 #include <asm/qspinlock.h>
+#include <asm/qrwlock.h>
 
 #endif /* _ASM_SPINLOCK_H */
diff --git a/arch/xtensa/include/asm/spinlock.h b/arch/xtensa/include/asm/spinlock.h
index 584b0de6f2ca..41c449ece2d8 100644
--- a/arch/xtensa/include/asm/spinlock.h
+++ b/arch/xtensa/include/asm/spinlock.h
@@ -12,8 +12,8 @@
 #define _XTENSA_SPINLOCK_H
 
 #include <asm/barrier.h>
-#include <asm/qrwlock.h>
 #include <asm/qspinlock.h>
+#include <asm/qrwlock.h>
 
 #define smp_mb__after_spinlock()	smp_mb()
 
-- 
2.18.1

Re: [PATCH] locking/arch: Move qrwlock.h include after qspinlock.h

[Guenter Roeck]

On 2/10/21 6:45 AM, Waiman Long wrote:
> The queued rwlock code has a dependency on the current spinlock
> implementation (likely to be qspinlock), but not vice versa. Including
> qrwlock.h before qspinlock.h can be problematic when expanding qrwlock
> functionality.
> 
> If both qspinlock.h and qrwlock.h are to be included, the qrwlock.h
> include should always be after qspinlock.h. Update the current set of
> asm/spinlock.h files to enforce that.
> 
> Signed-off-by: Waiman Long <longman@redhat.com>

There should be a Fixes: tag here. If the SHA of the offending commit is not
stable, there should be a better reference than "The queued rwlock code".

This patch fixes the build problem I had observed on mips. I also tested
xtensa:defconfig and arm64:defconfig with no problems observed.

Tested-by: Guenter Roeck <linux@roeck-us.net>

Guenter

> ---
>  arch/arm64/include/asm/spinlock.h  | 2 +-
>  arch/mips/include/asm/spinlock.h   | 2 +-
>  arch/xtensa/include/asm/spinlock.h | 2 +-
>  3 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/spinlock.h b/arch/arm64/include/asm/spinlock.h
> index 9083d6992603..0525c0b089ed 100644
> --- a/arch/arm64/include/asm/spinlock.h
> +++ b/arch/arm64/include/asm/spinlock.h
> @@ -5,8 +5,8 @@
>  #ifndef __ASM_SPINLOCK_H
>  #define __ASM_SPINLOCK_H
>  
> -#include <asm/qrwlock.h>
>  #include <asm/qspinlock.h>
> +#include <asm/qrwlock.h>
>  
>  /* See include/linux/spinlock.h */
>  #define smp_mb__after_spinlock()	smp_mb()
> diff --git a/arch/mips/include/asm/spinlock.h b/arch/mips/include/asm/spinlock.h
> index 8a88eb265516..6ce2117e49f6 100644
> --- a/arch/mips/include/asm/spinlock.h
> +++ b/arch/mips/include/asm/spinlock.h
> @@ -10,7 +10,6 @@
>  #define _ASM_SPINLOCK_H
>  
>  #include <asm/processor.h>
> -#include <asm/qrwlock.h>
>  
>  #include <asm-generic/qspinlock_types.h>
>  
> @@ -27,5 +26,6 @@ static inline void queued_spin_unlock(struct qspinlock *lock)
>  }
>  
>  #include <asm/qspinlock.h>
> +#include <asm/qrwlock.h>
>  
>  #endif /* _ASM_SPINLOCK_H */
> diff --git a/arch/xtensa/include/asm/spinlock.h b/arch/xtensa/include/asm/spinlock.h
> index 584b0de6f2ca..41c449ece2d8 100644
> --- a/arch/xtensa/include/asm/spinlock.h
> +++ b/arch/xtensa/include/asm/spinlock.h
> @@ -12,8 +12,8 @@
>  #define _XTENSA_SPINLOCK_H
>  
>  #include <asm/barrier.h>
> -#include <asm/qrwlock.h>
>  #include <asm/qspinlock.h>
> +#include <asm/qrwlock.h>
>  
>  #define smp_mb__after_spinlock()	smp_mb()
>  
> 

Re: [PATCH] locking/arch: Move qrwlock.h include after qspinlock.h

[Waiman Long]

On 2/10/21 10:05 AM, Guenter Roeck wrote:
> On 2/10/21 6:45 AM, Waiman Long wrote:
>> The queued rwlock code has a dependency on the current spinlock
>> implementation (likely to be qspinlock), but not vice versa. Including
>> qrwlock.h before qspinlock.h can be problematic when expanding qrwlock
>> functionality.
>>
>> If both qspinlock.h and qrwlock.h are to be included, the qrwlock.h
>> include should always be after qspinlock.h. Update the current set of
>> asm/spinlock.h files to enforce that.
>>
>> Signed-off-by: Waiman Long <longman@redhat.com>
> There should be a Fixes: tag here. If the SHA of the offending commit is not
> stable, there should be a better reference than "The queued rwlock code".
I originally have a Fixes tag when I was modifying the mips' 
asm/spinlock.h file. After I realize that there are more files to 
modify, I take that out. Anyway, the problem was exposed by Ben's 
qrwlock patch. So existing stable releases should still be fine without 
this patch.
>
> This patch fixes the build problem I had observed on mips. I also tested
> xtensa:defconfig and arm64:defconfig with no problems observed.
>
> Tested-by: Guenter Roeck <linux@roeck-us.net>

Thanks for the testing as I don't have a build environment to verify that.

Cheers,
Longman

Re: [PATCH] locking/arch: Move qrwlock.h include after qspinlock.h

[Ben Gardon]

On Wed, Feb 10, 2021 at 7:54 AM Waiman Long <longman@redhat.com> wrote:
>
> On 2/10/21 10:05 AM, Guenter Roeck wrote:
> > On 2/10/21 6:45 AM, Waiman Long wrote:
> >> The queued rwlock code has a dependency on the current spinlock
> >> implementation (likely to be qspinlock), but not vice versa. Including
> >> qrwlock.h before qspinlock.h can be problematic when expanding qrwlock
> >> functionality.
> >>
> >> If both qspinlock.h and qrwlock.h are to be included, the qrwlock.h
> >> include should always be after qspinlock.h. Update the current set of
> >> asm/spinlock.h files to enforce that.
> >>
> >> Signed-off-by: Waiman Long <longman@redhat.com>
> > There should be a Fixes: tag here. If the SHA of the offending commit is not
> > stable, there should be a better reference than "The queued rwlock code".
> I originally have a Fixes tag when I was modifying the mips'
> asm/spinlock.h file. After I realize that there are more files to
> modify, I take that out. Anyway, the problem was exposed by Ben's
> qrwlock patch. So existing stable releases should still be fine without
> this patch.
> >
> > This patch fixes the build problem I had observed on mips. I also tested
> > xtensa:defconfig and arm64:defconfig with no problems observed.
> >
> > Tested-by: Guenter Roeck <linux@roeck-us.net>
>
> Thanks for the testing as I don't have a build environment to verify that.
>
> Cheers,
> Longman
>

Thanks Longman and Guenter for developing and testing this fix! I
don't have the environment to test this either, but the patch looks
good to me.
Reviewed-by: Ben Gardon <bgardon@google.com>

Re: [PATCH] locking/arch: Move qrwlock.h include after qspinlock.h

[Thomas Bogendoerfer]

On Wed, Feb 10, 2021 at 09:45:56AM -0500, Waiman Long wrote:
> The queued rwlock code has a dependency on the current spinlock
> implementation (likely to be qspinlock), but not vice versa. Including
> qrwlock.h before qspinlock.h can be problematic when expanding qrwlock
> functionality.
> 
> If both qspinlock.h and qrwlock.h are to be included, the qrwlock.h
> include should always be after qspinlock.h. Update the current set of
> asm/spinlock.h files to enforce that.
> 
> Signed-off-by: Waiman Long <longman@redhat.com>
> ---
>  arch/arm64/include/asm/spinlock.h  | 2 +-
>  arch/mips/include/asm/spinlock.h   | 2 +-
>  arch/xtensa/include/asm/spinlock.h | 2 +-
>  3 files changed, 3 insertions(+), 3 deletions(-)

which tree should this go through ? I can take it via mips-next,
if everybody agrees.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]

Re: [PATCH] locking/arch: Move qrwlock.h include after qspinlock.h

[Paolo Bonzini]

On 10/02/21 17:19, Thomas Bogendoerfer wrote:
>>   arch/arm64/include/asm/spinlock.h  | 2 +-
>>   arch/mips/include/asm/spinlock.h   | 2 +-
>>   arch/xtensa/include/asm/spinlock.h | 2 +-
>>   3 files changed, 3 insertions(+), 3 deletions(-)
> which tree should this go through ? I can take it via mips-next,
> if everybody agrees.

The breakage is in the KVM tree, and the existing patch has acked-by 
from the locking primitives folks.  So I'll queue it there in order to 
limit the range that breaks bisection.

Paolo

Re: [PATCH] locking/arch: Move qrwlock.h include after qspinlock.h

[Thomas Bogendoerfer]

On Thu, Feb 11, 2021 at 01:59:35PM +0100, Paolo Bonzini wrote:
> On 10/02/21 17:19, Thomas Bogendoerfer wrote:
> > >   arch/arm64/include/asm/spinlock.h  | 2 +-
> > >   arch/mips/include/asm/spinlock.h   | 2 +-
> > >   arch/xtensa/include/asm/spinlock.h | 2 +-
> > >   3 files changed, 3 insertions(+), 3 deletions(-)
> > which tree should this go through ? I can take it via mips-next,
> > if everybody agrees.
> 
> The breakage is in the KVM tree, and the existing patch has acked-by from
> the locking primitives folks.  So I'll queue it there in order to limit the
> range that breaks bisection.

if it's not too late you can add by 

Acked-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]

Re: [PATCH] locking/arch: Move qrwlock.h include after qspinlock.h

[Paolo Bonzini]

On 10/02/21 15:45, Waiman Long wrote:
> The queued rwlock code has a dependency on the current spinlock
> implementation (likely to be qspinlock), but not vice versa. Including
> qrwlock.h before qspinlock.h can be problematic when expanding qrwlock
> functionality.
> 
> If both qspinlock.h and qrwlock.h are to be included, the qrwlock.h
> include should always be after qspinlock.h. Update the current set of
> asm/spinlock.h files to enforce that.
> 
> Signed-off-by: Waiman Long <longman@redhat.com>

arch/sparc/include/asm/spinlock_64.h is missing.  Also, the include in 
kernel/locking/qrwlock.c is not necessary (it may be there for aesthetic 
reasons, but it complicates thing in this case).

I'll send a v2 that is based on the kvm/next tree.

Paolo

> ---
>   arch/arm64/include/asm/spinlock.h  | 2 +-
>   arch/mips/include/asm/spinlock.h   | 2 +-
>   arch/xtensa/include/asm/spinlock.h | 2 +-
>   3 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/spinlock.h b/arch/arm64/include/asm/spinlock.h
> index 9083d6992603..0525c0b089ed 100644
> --- a/arch/arm64/include/asm/spinlock.h
> +++ b/arch/arm64/include/asm/spinlock.h
> @@ -5,8 +5,8 @@
>   #ifndef __ASM_SPINLOCK_H
>   #define __ASM_SPINLOCK_H
>   
> -#include <asm/qrwlock.h>
>   #include <asm/qspinlock.h>
> +#include <asm/qrwlock.h>
>   
>   /* See include/linux/spinlock.h */
>   #define smp_mb__after_spinlock()	smp_mb()
> diff --git a/arch/mips/include/asm/spinlock.h b/arch/mips/include/asm/spinlock.h
> index 8a88eb265516..6ce2117e49f6 100644
> --- a/arch/mips/include/asm/spinlock.h
> +++ b/arch/mips/include/asm/spinlock.h
> @@ -10,7 +10,6 @@
>   #define _ASM_SPINLOCK_H
>   
>   #include <asm/processor.h>
> -#include <asm/qrwlock.h>
>   
>   #include <asm-generic/qspinlock_types.h>
>   
> @@ -27,5 +26,6 @@ static inline void queued_spin_unlock(struct qspinlock *lock)
>   }
>   
>   #include <asm/qspinlock.h>
> +#include <asm/qrwlock.h>
>   
>   #endif /* _ASM_SPINLOCK_H */
> diff --git a/arch/xtensa/include/asm/spinlock.h b/arch/xtensa/include/asm/spinlock.h
> index 584b0de6f2ca..41c449ece2d8 100644
> --- a/arch/xtensa/include/asm/spinlock.h
> +++ b/arch/xtensa/include/asm/spinlock.h
> @@ -12,8 +12,8 @@
>   #define _XTENSA_SPINLOCK_H
>   
>   #include <asm/barrier.h>
> -#include <asm/qrwlock.h>
>   #include <asm/qspinlock.h>
> +#include <asm/qrwlock.h>
>   
>   #define smp_mb__after_spinlock()	smp_mb()
>   
> 

Re: [PATCH] locking/arch: Move qrwlock.h include after qspinlock.h

[Waiman Long]

On 2/10/21 1:28 PM, Paolo Bonzini wrote:
> On 10/02/21 15:45, Waiman Long wrote:
>> The queued rwlock code has a dependency on the current spinlock
>> implementation (likely to be qspinlock), but not vice versa. Including
>> qrwlock.h before qspinlock.h can be problematic when expanding qrwlock
>> functionality.
>>
>> If both qspinlock.h and qrwlock.h are to be included, the qrwlock.h
>> include should always be after qspinlock.h. Update the current set of
>> asm/spinlock.h files to enforce that.
>>
>> Signed-off-by: Waiman Long <longman@redhat.com>
>
> arch/sparc/include/asm/spinlock_64.h is missing.  Also, the include in 
> kernel/locking/qrwlock.c is not necessary (it may be there for 
> aesthetic reasons, but it complicates thing in this case).

Sorry for missing arch/sparc/include/asm/spinlock_64.h. I was just 
focusing on asm/spinlock.h and not aware that there are other variants 
there.

It is true that the asm/qrwlock.h include in qrwlock.c is not really 
necessary. I can't recall why it was there.

>
> I'll send a v2 that is based on the kvm/next tree.
>
> Paolo
>
Thanks for taking care of that.

Cheers,
Longman

[PATCH] locking/arch: Move qrwlock.h include after qspinlock.h

[Paolo Bonzini]

include/asm-generic/qrwlock.h was trying to get arch_spin_is_locked via
asm-generic/qspinlock.h.  However, this does not work because architectures
might be using queued rwlocks but not queued spinlocks (csky), or because they
might be defining their own queued_* macros before including asm/qspinlock.h.

To fix this, ensure that asm/spinlock.h always includes qrwlock.h after
defining arch_spin_is_locked (either directly for csky, or via
asm/qspinlock.h for other architectures).  The only inclusion elsewhere
is in kernel/locking/qrwlock.c.  That one is really unnecessary because
the file is only compiled in SMP configurations (config QUEUED_RWLOCKS
depends on SMP) and in that case linux/spinlock.h already includes
asm/qrwlock.h if needed, via asm/spinlock.h.

Reported-by: Guenter Roeck <linux@roeck-us.net>
Cc: Waiman Long <longman@redhat.com>
Fixes: 26128cb6c7e6 ("locking/rwlocks: Add contention detection for rwlocks")
Tested-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Ben Gardon <bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
	v1->v2: Fix sparc too.  Add a comment in qrwlock.h itself.
	Remove unnecessary inclusion in kernel/locking/qrwlock.c

 arch/arm64/include/asm/spinlock.h    | 2 +-
 arch/mips/include/asm/spinlock.h     | 2 +-
 arch/sparc/include/asm/spinlock_64.h | 2 +-
 arch/xtensa/include/asm/spinlock.h   | 2 +-
 include/asm-generic/qrwlock.h        | 3 ++-
 kernel/locking/qrwlock.c             | 1 -
 6 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/include/asm/spinlock.h b/arch/arm64/include/asm/spinlock.h
index 9083d6992603..0525c0b089ed 100644
--- a/arch/arm64/include/asm/spinlock.h
+++ b/arch/arm64/include/asm/spinlock.h
@@ -5,8 +5,8 @@
 #ifndef __ASM_SPINLOCK_H
 #define __ASM_SPINLOCK_H
 
-#include <asm/qrwlock.h>
 #include <asm/qspinlock.h>
+#include <asm/qrwlock.h>
 
 /* See include/linux/spinlock.h */
 #define smp_mb__after_spinlock()	smp_mb()
diff --git a/arch/mips/include/asm/spinlock.h b/arch/mips/include/asm/spinlock.h
index 8a88eb265516..6ce2117e49f6 100644
--- a/arch/mips/include/asm/spinlock.h
+++ b/arch/mips/include/asm/spinlock.h
@@ -10,7 +10,6 @@
 #define _ASM_SPINLOCK_H
 
 #include <asm/processor.h>
-#include <asm/qrwlock.h>
 
 #include <asm-generic/qspinlock_types.h>
 
@@ -27,5 +26,6 @@ static inline void queued_spin_unlock(struct qspinlock *lock)
 }
 
 #include <asm/qspinlock.h>
+#include <asm/qrwlock.h>
 
 #endif /* _ASM_SPINLOCK_H */
diff --git a/arch/sparc/include/asm/spinlock_64.h b/arch/sparc/include/asm/spinlock_64.h
index 7fc82a233f49..3a9a0b0c7465 100644
--- a/arch/sparc/include/asm/spinlock_64.h
+++ b/arch/sparc/include/asm/spinlock_64.h
@@ -11,8 +11,8 @@
 
 #include <asm/processor.h>
 #include <asm/barrier.h>
-#include <asm/qrwlock.h>
 #include <asm/qspinlock.h>
+#include <asm/qrwlock.h>
 
 #endif /* !(__ASSEMBLY__) */
 
diff --git a/arch/xtensa/include/asm/spinlock.h b/arch/xtensa/include/asm/spinlock.h
index 584b0de6f2ca..41c449ece2d8 100644
--- a/arch/xtensa/include/asm/spinlock.h
+++ b/arch/xtensa/include/asm/spinlock.h
@@ -12,8 +12,8 @@
 #define _XTENSA_SPINLOCK_H
 
 #include <asm/barrier.h>
-#include <asm/qrwlock.h>
 #include <asm/qspinlock.h>
+#include <asm/qrwlock.h>
 
 #define smp_mb__after_spinlock()	smp_mb()
 
diff --git a/include/asm-generic/qrwlock.h b/include/asm-generic/qrwlock.h
index 0020d3b820a7..7ae0ece07b4e 100644
--- a/include/asm-generic/qrwlock.h
+++ b/include/asm-generic/qrwlock.h
@@ -14,7 +14,8 @@
 #include <asm/processor.h>
 
 #include <asm-generic/qrwlock_types.h>
-#include <asm-generic/qspinlock.h>
+
+/* Must be included from asm/spinlock.h after defining arch_spin_is_locked.  */
 
 /*
  * Writer states & reader shift and bias.
diff --git a/kernel/locking/qrwlock.c b/kernel/locking/qrwlock.c
index fe9ca92faa2a..4786dd271b45 100644
--- a/kernel/locking/qrwlock.c
+++ b/kernel/locking/qrwlock.c
@@ -12,7 +12,6 @@
 #include <linux/percpu.h>
 #include <linux/hardirq.h>
 #include <linux/spinlock.h>
-#include <asm/qrwlock.h>
 
 /**
  * queued_read_lock_slowpath - acquire read lock of a queue rwlock
-- 
2.26.2