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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>
This commit is contained in:
Kent Overstreet 2023-10-24 14:46:58 -04:00
parent cd063c8b9e
commit 2bce6368c4
2 changed files with 4 additions and 4 deletions
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2
include/linux/closure.h
View File

@ -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)

6
lib/closure.c
View File

@ -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);