| Message ID | 1538079759.qxp8zh3nwh.astroid@alex-archsus.none (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Headers | show |
| Series | mm: fix z3fold warnings on CONFIG_SMP=n | expand |
On Thu, Sep 27, 2018 at 4:27 PM Alex Xu (Hello71) <alex_y_xu@yahoo.ca> wrote: > > Spinlocks are always lockable on UP systems, even if they were just > locked. i think it would be much better to just use either assert_spin_locked() or just spin_is_locked(), instead of an #ifdef. > > Cc: Dan Streetman <ddstreet@ieee.org> > Signed-off-by: Alex Xu (Hello71) <alex_y_xu@yahoo.ca> > --- > mm/z3fold.c | 13 ++++++++++--- > 1 file changed, 10 insertions(+), 3 deletions(-) > > diff --git a/mm/z3fold.c b/mm/z3fold.c > index 4b366d181..4e6ad2de4 100644 > --- a/mm/z3fold.c > +++ b/mm/z3fold.c > @@ -202,6 +202,13 @@ static inline void z3fold_page_lock(struct z3fold_header *zhdr) > spin_lock(&zhdr->page_lock); > } > > +static inline void z3fold_page_ensure_locked(struct z3fold_header *zhdr) > +{ > +#ifdef CONFIG_SMP > + WARN_ON(z3fold_page_trylock(zhdr)); > +#endif > +} > + > /* Try to lock a z3fold page */ > static inline int z3fold_page_trylock(struct z3fold_header *zhdr) > { > @@ -277,7 +284,7 @@ static void release_z3fold_page_locked(struct kref *ref) > { > struct z3fold_header *zhdr = container_of(ref, struct z3fold_header, > refcount); > - WARN_ON(z3fold_page_trylock(zhdr)); > + z3fold_page_ensure_locked(zhdr); > __release_z3fold_page(zhdr, true); > } > > @@ -289,7 +296,7 @@ static void release_z3fold_page_locked_list(struct kref *ref) > list_del_init(&zhdr->buddy); > spin_unlock(&zhdr->pool->lock); > > - WARN_ON(z3fold_page_trylock(zhdr)); > + z3fold_page_ensure_locked(zhdr); > __release_z3fold_page(zhdr, true); > } > > @@ -403,7 +410,7 @@ static void do_compact_page(struct z3fold_header *zhdr, bool locked) > > page = virt_to_page(zhdr); > if (locked) > - WARN_ON(z3fold_page_trylock(zhdr)); > + z3fold_page_ensure_locked(zhdr); > else > z3fold_page_lock(zhdr); > if (WARN_ON(!test_and_clear_bit(NEEDS_COMPACTING, &page->private))) { > -- > 2.19.0 >
Quoting Dan Streetman (2018-09-27 20:41:21) > On Thu, Sep 27, 2018 at 4:27 PM Alex Xu (Hello71) <alex_y_xu@yahoo.ca> wrote: > > > > Spinlocks are always lockable on UP systems, even if they were just > > locked. > > i think it would be much better to just use either > assert_spin_locked() or just spin_is_locked(), instead of an #ifdef. > I wrote a longer response and then learned about the WARN_ON_SMP macro, so I'll just use that instead. Original response below: I thought about using assert_spin_locked, but I wanted to keep the existing behavior, and it seems to make sense to try to lock the page if we forgot to lock it earlier? Maybe not though; I don't understand this code completely. I did write a version of z3fold_page_ensure_locked with "if (assert_spin_locked(...))" but not only did that look even worse, it doesn't even work, because assert_spin_locked is a statement on UP systems, not an expression. It might be worth adding a ensure_spin_locked function that does that though... spin_is_locked currently still always returns 0 "on CONFIG_SMP=n builds with CONFIG_DEBUG_SPINLOCK=n", so that would just return us to the same problem of checking CONFIG_SMP.
diff --git a/mm/z3fold.c b/mm/z3fold.c index 4b366d181..4e6ad2de4 100644 --- a/mm/z3fold.c +++ b/mm/z3fold.c @@ -202,6 +202,13 @@ static inline void z3fold_page_lock(struct z3fold_header *zhdr) spin_lock(&zhdr->page_lock); } +static inline void z3fold_page_ensure_locked(struct z3fold_header *zhdr) +{ +#ifdef CONFIG_SMP + WARN_ON(z3fold_page_trylock(zhdr)); +#endif +} + /* Try to lock a z3fold page */ static inline int z3fold_page_trylock(struct z3fold_header *zhdr) { @@ -277,7 +284,7 @@ static void release_z3fold_page_locked(struct kref *ref) { struct z3fold_header *zhdr = container_of(ref, struct z3fold_header, refcount); - WARN_ON(z3fold_page_trylock(zhdr)); + z3fold_page_ensure_locked(zhdr); __release_z3fold_page(zhdr, true); } @@ -289,7 +296,7 @@ static void release_z3fold_page_locked_list(struct kref *ref) list_del_init(&zhdr->buddy); spin_unlock(&zhdr->pool->lock); - WARN_ON(z3fold_page_trylock(zhdr)); + z3fold_page_ensure_locked(zhdr); __release_z3fold_page(zhdr, true); } @@ -403,7 +410,7 @@ static void do_compact_page(struct z3fold_header *zhdr, bool locked) page = virt_to_page(zhdr); if (locked) - WARN_ON(z3fold_page_trylock(zhdr)); + z3fold_page_ensure_locked(zhdr); else z3fold_page_lock(zhdr); if (WARN_ON(!test_and_clear_bit(NEEDS_COMPACTING, &page->private))) {
Spinlocks are always lockable on UP systems, even if they were just locked. Cc: Dan Streetman <ddstreet@ieee.org> Signed-off-by: Alex Xu (Hello71) <alex_y_xu@yahoo.ca> --- mm/z3fold.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-)