Commit 2bce6368 authored by Kent Overstreet's avatar Kent Overstreet
Browse files

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: default avatarKent Overstreet <kent.overstreet@linux.dev>
parent cd063c8b

include/linux/closure.h

+0 −2
Original line number Diff line number Diff line
@@ -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)

lib/closure.c

+4 −2
Original line number Diff line number Diff line
@@ -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);