On 04/08/2018 02:14 PM, Paul E. McKenney wrote: > On Fri, Apr 06, 2018 at 11:58:25PM +0200, Andrea Parri wrote: >> On Fri, Apr 06, 2018 at 02:08:16PM -0700, Randy Dunlap wrote: >>> On 04/06/2018 02:07 PM, Paul E. McKenney wrote: >>>> On Fri, Apr 06, 2018 at 02:01:41PM -0700, Randy Dunlap wrote: >>>>> On 04/06/2018 12:47 PM, Andrea Parri wrote: >>>>>> There appeared to be a certain, recurrent uncertainty concerning the >>>>>> semantics of spin_is_locked(), likely a consequence of the fact that >>>>>> this semantics remains undocumented or that it has been historically >>>>>> linked to the (likewise unclear) semantics of spin_unlock_wait(). >>>>>> >>>>>> A recent auditing [1] of the callers of the primitive confirmed that >>>>>> none of them are relying on particular ordering guarantees; document >>>>>> this semantics by adding a docbook header to spin_is_locked(). Also, >>>>>> describe behaviors specific to certain CONFIG_SMP=n builds. >>>>>> >>>>>> [1] https://marc.info/?l=linux-kernel&m=151981440005264&w=2 >>>>>> https://marc.info/?l=linux-kernel&m=152042843808540&w=2 >>>>>> https://marc.info/?l=linux-kernel&m=152043346110262&w=2 >>>>>> >>>>>> Co-Developed-by: Andrea Parri <andrea.pa...@amarulasolutions.com> >>>>>> Co-Developed-by: Alan Stern <st...@rowland.harvard.edu> >>>>>> Co-Developed-by: David Howells <dhowe...@redhat.com> >>>>>> Signed-off-by: Andrea Parri <andrea.pa...@amarulasolutions.com> >>>>>> Signed-off-by: Alan Stern <st...@rowland.harvard.edu> >>>>>> Signed-off-by: David Howells <dhowe...@redhat.com> >>>>>> Cc: Will Deacon <will.dea...@arm.com> >>>>>> Cc: Peter Zijlstra <pet...@infradead.org> >>>>>> Cc: Boqun Feng <boqun.f...@gmail.com> >>>>>> Cc: Nicholas Piggin <npig...@gmail.com> >>>>>> Cc: Jade Alglave <j.algl...@ucl.ac.uk> >>>>>> Cc: Luc Maranget <luc.maran...@inria.fr> >>>>>> Cc: "Paul E. McKenney" <paul...@linux.vnet.ibm.com> >>>>>> Cc: Akira Yokosawa <aki...@gmail.com> >>>>>> Cc: Ingo Molnar <mi...@kernel.org> >>>>>> --- >>>>>> include/linux/spinlock.h | 18 ++++++++++++++++++ >>>>>> 1 file changed, 18 insertions(+) >>>>>> >>>>>> diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h >>>>>> index 4894d322d2584..1e8a464358384 100644 >>>>>> --- a/include/linux/spinlock.h >>>>>> +++ b/include/linux/spinlock.h >>>>>> @@ -380,6 +380,24 @@ static __always_inline int >>>>>> spin_trylock_irq(spinlock_t *lock) >>>>>> raw_spin_trylock_irqsave(spinlock_check(lock), flags); \ >>>>>> }) >>>>>> >>>>>> +/** >>>>>> + * spin_is_locked() - Check whether a spinlock is locked. >>>>>> + * @lock: Pointer to the spinlock. >>>>>> + * >>>>>> + * This function is NOT required to provide any memory ordering >>>>>> + * guarantees; it could be used for debugging purposes or, when >>>>>> + * additional synchronization is needed, accompanied with other >>>>>> + * constructs (memory barriers) enforcing the synchronization. >>>>>> + * >>>>>> + * Returns: 1 if @lock is locked, 0 otherwise. >>>>> >>>>> Sorry, minor nit: >>>>> s/Returns:/Return:/ >>>>> (according to kernel-doc.rst) >>>>> >>>>> although I agree that "Returns:" is better. >>>>> [I should have changed that years ago.] >>>> >>>> Agreed, English grammar and templates often seem to conflict. >>>> >>>> So should we change this comment, or are you instead proposing to add >>>> "Returns:" as valid kernel-doc? >>> >>> Please change this patch to current doc syntax. >>> Any changes to kernel-doc syntax would come later. > > Are you sure? > > $ git grep "\* Returns:" | wc -l > 2470 > $ git grep "\* Return:" | wc -l > 4144 > > Looks like more than a third of them are already "Returns:". ;-) > >> Paul: I understand that you're going to do this change "in place"; please >> let me know if I'm wrong/if you need a new submission. > > If Randy is certain that he would like to continue propagating > this grammatical infelicity, sure. ;-)
eh? Well, Documentation/doc-guide/kernel-doc.rst says "Return:", but it appears that it does not matter to scripts/kernel-doc -- it's just the name of a "section" of the documentation and can be spelled any way! oh well. :) Acked-by: Randy Dunlap <rdun...@infradead.org> Thanks. -- ~Randy
