closures: Better memory barriers

atomic_(dec|sub)_return_release() are a thing now - use them.

Also, delete the useless barrier in set_closure_fn(): it's redundant
with the memory barrier in closure_put(0.

Since closure_put() would now otherwise just have a release barrier, we
also need a new barrier when the ref hits 0 -
smp_acquire__after_ctrl_dep().

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/include/linux/closure.h b/include/linux/closure.h
index 722a586..bdab170 100644 (file)
--- a/include/linux/closure.h
+++ b/include/linux/closure.h
@@ -233,8 +233,6 @@ static inline void set_closure_fn(struct closure *cl, closure_fn *fn,
        closure_set_ip(cl);
        cl->fn = fn;
        cl->wq = wq;
-       /* between atomic_dec() in closure_put() */
-       smp_mb__before_atomic();
 }
 
 static inline void closure_queue(struct closure *cl)

diff --git a/lib/closure.c b/lib/closure.c
index 0855e69..501dfa2 100644 (file)
--- a/lib/closure.c
+++ b/lib/closure.c
@@ -21,6 +21,8 @@ static inline void closure_put_after_sub(struct closure *cl, int flags)
        BUG_ON(!r && (flags & ~CLOSURE_DESTRUCTOR));
 
        if (!r) {
+               smp_acquire__after_ctrl_dep();
+
                if (cl->fn && !(flags & CLOSURE_DESTRUCTOR)) {
                        atomic_set(&cl->remaining,
                                   CLOSURE_REMAINING_INITIALIZER);
@@ -43,7 +45,7 @@ static inline void closure_put_after_sub(struct closure *cl, int flags)
 /* For clearing flags with the same atomic op as a put */
 void closure_sub(struct closure *cl, int v)
 {
-       closure_put_after_sub(cl, atomic_sub_return(v, &cl->remaining));
+       closure_put_after_sub(cl, atomic_sub_return_release(v, &cl->remaining));
 }
 EXPORT_SYMBOL(closure_sub);
 
@@ -52,7 +54,7 @@ EXPORT_SYMBOL(closure_sub);
  */
 void closure_put(struct closure *cl)
 {
-       closure_put_after_sub(cl, atomic_dec_return(&cl->remaining));
+       closure_put_after_sub(cl, atomic_dec_return_release(&cl->remaining));
 }
 EXPORT_SYMBOL(closure_put);