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SubjectRe: [PATCH] locking/mutex: initialize osq lock in __MUTEX_INITIALIZER()
On Mon, Mar 29, 2021 at 03:50:56PM +0100, Will Deacon wrote:
> On Mon, Mar 29, 2021 at 12:15:16AM -0700, Nikitas Angelinas wrote:
> > Since __MUTEX_INITIALIZER() is used on memory that is initialized to 0
> > anyway this change should not have an effect, but it seems better to
> > initialize osq explicitly for completeness, as done in other macros and
> > functions that initialize mutex and rwsem.
> >
> > Signed-off-by: Nikitas Angelinas <nikitas.angelinas@gmail.com>
> > ---
> > include/linux/mutex.h | 8 ++++++++
> > 1 file changed, 8 insertions(+)
> >
> > diff --git a/include/linux/mutex.h b/include/linux/mutex.h
> > index 515cff7..bff47f8 100644
> > --- a/include/linux/mutex.h
> > +++ b/include/linux/mutex.h
> > @@ -129,10 +129,18 @@ do { \
> > # define __DEP_MAP_MUTEX_INITIALIZER(lockname)
> > #endif
> >
> > +#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
> > +# define __OSQ_MUTEX_INITIALIZER(lockname) \
> > + , .osq = OSQ_LOCK_UNLOCKED
> > +#else
> > +# define __OSQ_MUTEX_INITIALIZER(lockname)
> > +#endif
> > +
> > #define __MUTEX_INITIALIZER(lockname) \
> > { .owner = ATOMIC_LONG_INIT(0) \
> > , .wait_lock = __SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
> > , .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
> > + __OSQ_MUTEX_INITIALIZER(lockname) \
>
> You don't need the lockname parameter for this macro.
>
> Will

Hi,

Please excuse this late reply.

I included the unnecessary lockname parameter as the counterpart macro in
__RWSEM_INITIALIZER(), __RWSEM_OPT_INIT() and also __RWSEM_COUNT_INIT() do the
same thing, thinking that was done on purpose, e.g. so that all macros used take
a parameter in order to satisfy some dubious notion of symmetry; I realize this
is not a good reason, of course.

I'll send a v2, possibly in a series with changes to the aforementioned bits in
rwsem, fwiw.


Cheers,
Nikitas

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