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SubjectRe: [PATCH v2 06/28] locking/rwlocks: Add contention detection for rwlocks
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On 2/9/21 5:25 PM, Guenter Roeck wrote:
> On Tue, Feb 09, 2021 at 04:46:02PM -0500, Waiman Long wrote:
>> On 2/9/21 3:39 PM, Guenter Roeck wrote:
>>> On Tue, Feb 02, 2021 at 10:57:12AM -0800, Ben Gardon wrote:
>>>> rwlocks do not currently have any facility to detect contention
>>>> like spinlocks do. In order to allow users of rwlocks to better manage
>>>> latency, add contention detection for queued rwlocks.
>>>>
>>>> CC: Ingo Molnar <mingo@redhat.com>
>>>> CC: Will Deacon <will@kernel.org>
>>>> Acked-by: Peter Zijlstra <peterz@infradead.org>
>>>> Acked-by: Davidlohr Bueso <dbueso@suse.de>
>>>> Acked-by: Waiman Long <longman@redhat.com>
>>>> Acked-by: Paolo Bonzini <pbonzini@redhat.com>
>>>> Signed-off-by: Ben Gardon <bgardon@google.com>
>>> When building mips:defconfig, this patch results in:
>>>
>>> Error log:
>>> In file included from include/linux/spinlock.h:90,
>>> from include/linux/ipc.h:5,
>>> from include/uapi/linux/sem.h:5,
>>> from include/linux/sem.h:5,
>>> from include/linux/compat.h:14,
>>> from arch/mips/kernel/asm-offsets.c:12:
>>> arch/mips/include/asm/spinlock.h:17:28: error: redefinition of 'queued_spin_unlock'
>>> 17 | #define queued_spin_unlock queued_spin_unlock
>>> | ^~~~~~~~~~~~~~~~~~
>>> arch/mips/include/asm/spinlock.h:22:20: note: in expansion of macro 'queued_spin_unlock'
>>> 22 | static inline void queued_spin_unlock(struct qspinlock *lock)
>>> | ^~~~~~~~~~~~~~~~~~
>>> In file included from include/asm-generic/qrwlock.h:17,
>>> from ./arch/mips/include/generated/asm/qrwlock.h:1,
>>> from arch/mips/include/asm/spinlock.h:13,
>>> from include/linux/spinlock.h:90,
>>> from include/linux/ipc.h:5,
>>> from include/uapi/linux/sem.h:5,
>>> from include/linux/sem.h:5,
>>> from include/linux/compat.h:14,
>>> from arch/mips/kernel/asm-offsets.c:12:
>>> include/asm-generic/qspinlock.h:94:29: note: previous definition of 'queued_spin_unlock' was here
>>> 94 | static __always_inline void queued_spin_unlock(struct qspinlock *lock)
>>> | ^~~~~~~~~~~~~~~~~~
>> I think the compile error is caused by the improper header file inclusion
>> ordering. Can you try the following change to see if it can fix the compile
>> error?
>>
> That results in:
>
> In file included from ./arch/mips/include/generated/asm/qrwlock.h:1,
> from ./arch/mips/include/asm/spinlock.h:13,
> from ./include/linux/spinlock.h:90,
> from ./include/linux/ipc.h:5,
> from ./include/uapi/linux/sem.h:5,
> from ./include/linux/sem.h:5,
> from ./include/linux/compat.h:14,
> from arch/mips/kernel/asm-offsets.c:12:
> ./include/asm-generic/qrwlock.h: In function 'queued_rwlock_is_contended':
> ./include/asm-generic/qrwlock.h:127:9: error: implicit declaration of function 'arch_spin_is_locked'
>
> Guenter

It is because in arch/mips/include/asm/spinlock.h, asm/qrwlock.h is
included before asm/qspinlock.h. The compilation error should be gone if
the asm/qrwlock.h is removed or moved after asm/qspinlock.h.

I did a x86 build and there was no compilation issue.

Cheers,
Longman

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