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SubjectRe: [patch 1/2] spinlocks: check spinlock_t/rwlock_t argument type on non-SMP builds
Andrew Morton wrote:
> On Mon, 21 Sep 2009 09:43:52 +0200
> Ingo Molnar <mingo@elte.hu> wrote:
>
>> * akpm@linux-foundation.org <akpm@linux-foundation.org> wrote:
>>
>>> From: David Kilroy <kilroyd@googlemail.com>
>>>
>>> When writing code for UP without CONFIG_DEBUG_SPINLOCK it's easy to get
>>> the first argument to the spinlock/rwlock functions wrong. This is
>>> because the parameter is not actually used in this configuration.
>>>
>>> Typically you will only find out it's wrong
>>> * by rebuilding with CONFIG_SMP or CONFIG_DEBUG_SPINLOCK
>>> * after you've submitted your beautiful patch series.
>>>
>>> The first means a long wait, and the latter is a bit late.
>>>
>>> Change the intermediate macros into inline functions.
>>>
>>> Signed-off-by: David Kilroy <kilroyd@googlemail.com>
>>> Cc: Ingo Molnar <mingo@elte.hu>
>>> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
>>> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
>>> ---
>>>
>>> include/linux/spinlock.h | 6 -
>>> include/linux/spinlock_api_up.h | 118 ++++++++++++++++++++++--------
>>> 2 files changed, 92 insertions(+), 32 deletions(-)
>>>
>>> diff -puN include/linux/spinlock.h~spinlocks-check-spinlock_t-rwlock_t-argument-type-on-non-smp-builds include/linux/spinlock.h
>>> --- a/include/linux/spinlock.h~spinlocks-check-spinlock_t-rwlock_t-argument-type-on-non-smp-builds
>>> +++ a/include/linux/spinlock.h
>>> @@ -240,17 +240,17 @@ static inline void smp_mb__after_lock(vo
>>> #define spin_lock_irqsave(lock, flags) \
>>> do { \
>>> typecheck(unsigned long, flags); \
>>> - _spin_lock_irqsave(lock, flags); \
>>> + _spin_lock_irqsave(lock, &flags); \
>>> } while (0)
>>> #define read_lock_irqsave(lock, flags) \
>>> do { \
>>> typecheck(unsigned long, flags); \
>>> - _read_lock_irqsave(lock, flags); \
>>> + _read_lock_irqsave(lock, &flags); \
>>> } while (0)
>> these bits broke the Alpha build:
>>
>> /home/mingo/tip/arch/alpha/include/asm/core_t2.h: In function 't2_readb':
>> /home/mingo/tip/arch/alpha/include/asm/core_t2.h:451: error: '_spin_lock_irqsave' is static but used in inline function 't2_readb' which is not static
>
> hm. What the heck does that mean?
>
> __EXTERN_INLINE u8 t2_readb(const volatile void __iomem *xaddr)
>
> Something to do with the extern-inline?

This came up the last time this went into Ingos tree. And yes, it's the
extern inlines using the spinlock functions that causes the error.

> Do you have the .config? My alpha builds went OK.

Last I checked, you need to have:
CONFIG_SMP=N
CONFIG_DEBUG_SPINLOCK=N

The latter gets auto-selected, so I set:
CONFIG_DEBUG_LOCK_ALLOC=N
CONFIG_LOCK_STAT=N
CONFIG_PROVE_LOCKING=N
CONFIG_LOCK_STAT=N


Regards,

Dave.


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