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io_uring/eventfd: clean up rcu locking 

Conditional locking is never welcome if there are better options. Move
rcu locking into io_eventfd_signal(), make it unconditional and use
guards. It also helps with sparse warnings.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/91a925e708ca8a5aa7fee61f96d29b24ea9adeaf.1745493845.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
pull/1250/head
Pavel Begunkov 2025-04-24 12:31:17 +01:00 committed by Jens Axboe
parent 62f666df76
commit da01f60f8a
1 changed files with 7 additions and 17 deletions
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24
io_uring/eventfd.c
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@ -47,13 +47,6 @@ static void io_eventfd_do_signal(struct rcu_head *rcu)
io_eventfd_put(ev_fd); io_eventfd_put(ev_fd);
} }
static void io_eventfd_release(struct io_ev_fd *ev_fd, bool put_ref)
{
if (put_ref)
io_eventfd_put(ev_fd);
rcu_read_unlock();
}
/* /*
* Returns true if the caller should put the ev_fd reference, false if not. * Returns true if the caller should put the ev_fd reference, false if not.
*/ */
@ -89,11 +82,6 @@ static struct io_ev_fd *io_eventfd_grab(struct io_ring_ctx *ctx)
{ {
struct io_ev_fd *ev_fd; struct io_ev_fd *ev_fd;
if (READ_ONCE(ctx->rings->cq_flags) & IORING_CQ_EVENTFD_DISABLED)
return NULL;
rcu_read_lock();
/* /*
* rcu_dereference ctx->io_ev_fd once and use it for both for checking * rcu_dereference ctx->io_ev_fd once and use it for both for checking
* and eventfd_signal * and eventfd_signal
@ -108,15 +96,18 @@ static struct io_ev_fd *io_eventfd_grab(struct io_ring_ctx *ctx)
if (io_eventfd_trigger(ev_fd) && refcount_inc_not_zero(&ev_fd->refs)) if (io_eventfd_trigger(ev_fd) && refcount_inc_not_zero(&ev_fd->refs))
return ev_fd; return ev_fd;
rcu_read_unlock();
return NULL; return NULL;
} }
void io_eventfd_signal(struct io_ring_ctx *ctx, bool cqe_event) void io_eventfd_signal(struct io_ring_ctx *ctx, bool cqe_event)
{ {
bool skip = false, put_ref = true; bool skip = false;
struct io_ev_fd *ev_fd; struct io_ev_fd *ev_fd;
if (READ_ONCE(ctx->rings->cq_flags) & IORING_CQ_EVENTFD_DISABLED)
return;
guard(rcu)();
ev_fd = io_eventfd_grab(ctx); ev_fd = io_eventfd_grab(ctx);
if (!ev_fd) if (!ev_fd)
return; return;
@ -137,9 +128,8 @@ void io_eventfd_signal(struct io_ring_ctx *ctx, bool cqe_event)
spin_unlock(&ctx->completion_lock); spin_unlock(&ctx->completion_lock);
} }
if (!skip) if (skip || __io_eventfd_signal(ev_fd))
put_ref = __io_eventfd_signal(ev_fd); io_eventfd_put(ev_fd);
io_eventfd_release(ev_fd, put_ref);
} }
int io_eventfd_register(struct io_ring_ctx *ctx, void __user *arg, int io_eventfd_register(struct io_ring_ctx *ctx, void __user *arg,