| Message ID | 20240921080307.185186-7-axboe@kernel.dk (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Move eventfd cq tracking into io_ev_fd | expand |
On 9/21/24 1:59 AM, Jens Axboe wrote:> 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. Of course forgot to refresh io_uring_types.h as well, so this patch is missing the hunk that deletes it from io_ring_ctx. Refreshed version below, that's the only change. diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h index 4b9ba523978d..0deec302595a 100644 --- a/include/linux/io_uring_types.h +++ b/include/linux/io_uring_types.h @@ -413,10 +413,6 @@ struct io_ring_ctx { DECLARE_HASHTABLE(napi_ht, 4); #endif - - /* protected by ->completion_lock */ - unsigned evfd_last_cq_tail; - /* * If IORING_SETUP_NO_MMAP is used, then the below holds * the gup'ed pages for the two rings, and the sqes. diff --git a/io_uring/eventfd.c b/io_uring/eventfd.c index d1fdecd0c458..fab936d31ba8 100644 --- a/io_uring/eventfd.c +++ b/io_uring/eventfd.c @@ -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; - - spin_lock(&ctx->completion_lock); - - /* - * 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. - */ - skip = ctx->cached_cq_tail == ctx->evfd_last_cq_tail; - ctx->evfd_last_cq_tail = ctx->cached_cq_tail; - spin_unlock(&ctx->completion_lock); - if (skip) - return; + struct io_ev_fd *ev_fd; - io_eventfd_signal(ctx); + 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 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. + */ + 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) + 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;
diff --git a/io_uring/eventfd.c b/io_uring/eventfd.c index d1fdecd0c458..fab936d31ba8 100644 --- a/io_uring/eventfd.c +++ b/io_uring/eventfd.c @@ -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; - - spin_lock(&ctx->completion_lock); - - /* - * 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. - */ - skip = ctx->cached_cq_tail == ctx->evfd_last_cq_tail; - ctx->evfd_last_cq_tail = ctx->cached_cq_tail; - spin_unlock(&ctx->completion_lock); - if (skip) - return; + struct io_ev_fd *ev_fd; - io_eventfd_signal(ctx); + 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 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. + */ + 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) + 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;
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. Signed-off-by: Jens Axboe <axboe@kernel.dk> --- io_uring/eventfd.c | 50 +++++++++++++++++++++++++++------------------- 1 file changed, 29 insertions(+), 21 deletions(-)