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io_uring/eventfd: move ctx->evfd_last_cq_tail into io_ev_fd

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Everything else about the io_uring eventfd support is nicely kept
private to that code, except the cached_cq_tail tracking. With
everything else in place, move io_eventfd_flush_signal() to using
the ev_fd grab+release helpers, which then enables the direct use of
io_ev_fd for this tracking too.

Link: https://lore.kernel.org/r/20240921080307.185186-7-axboe@kernel.dk
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2024-09-21 01:59:52 -06:00
parent 83a4f865e2
commit f4bb2f65bb
1 changed files with 27 additions and 19 deletions
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40
io_uring/eventfd.c
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@ -13,10 +13,12 @@
struct io_ev_fd {
struct eventfd_ctx *cq_ev_fd;
unsigned int eventfd_async: 1;
struct rcu_head rcu;
unsigned int eventfd_async;
/* protected by ->completion_lock */
unsigned last_cq_tail;
refcount_t refs;
atomic_t ops;
struct rcu_head rcu;
};
enum {
@ -123,25 +125,31 @@ void io_eventfd_signal(struct io_ring_ctx *ctx)
void io_eventfd_flush_signal(struct io_ring_ctx *ctx)
{
bool skip;
struct io_ev_fd *ev_fd;
spin_lock(&ctx->completion_lock);
ev_fd = io_eventfd_grab(ctx);
if (ev_fd) {
bool skip, put_ref = true;
/*
* Eventfd should only get triggered when at least one event has been
* posted. Some applications rely on the eventfd notification count
* only changing IFF a new CQE has been added to the CQ ring. There's
* no depedency on 1:1 relationship between how many times this
* function is called (and hence the eventfd count) and number of CQEs
* posted to the CQ ring.
* Eventfd should only get triggered when at least one event
* has been posted. Some applications rely on the eventfd
* notification count only changing IFF a new CQE has been
* added to the CQ ring. There's no dependency on 1:1
* relationship between how many times this function is called
* (and hence the eventfd count) and number of CQEs posted to
* the CQ ring.
*/
skip = ctx->cached_cq_tail == ctx->evfd_last_cq_tail;
ctx->evfd_last_cq_tail = ctx->cached_cq_tail;
spin_lock(&ctx->completion_lock);
skip = ctx->cached_cq_tail == ev_fd->last_cq_tail;
ev_fd->last_cq_tail = ctx->cached_cq_tail;
spin_unlock(&ctx->completion_lock);
if (skip)
return;
io_eventfd_signal(ctx);
if (!skip)
put_ref = __io_eventfd_signal(ev_fd);
io_eventfd_release(ev_fd, put_ref);
}
}
int io_eventfd_register(struct io_ring_ctx *ctx, void __user *arg,
@ -172,7 +180,7 @@ int io_eventfd_register(struct io_ring_ctx *ctx, void __user *arg,
}
spin_lock(&ctx->completion_lock);
ctx->evfd_last_cq_tail = ctx->cached_cq_tail;
ev_fd->last_cq_tail = ctx->cached_cq_tail;
spin_unlock(&ctx->completion_lock);
ev_fd->eventfd_async = eventfd_async;