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io_uring/eventfd: abstract out ev_fd grab + release helpers

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In preparation for needing the ev_fd grabbing (and releasing) from
another path, abstract out two helpers for that.

Link: https://lore.kernel.org/r/20240921080307.185186-6-axboe@kernel.dk
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2024-09-21 01:59:51 -06:00
parent 3ca5a35604
commit 83a4f865e2
1 changed files with 30 additions and 11 deletions
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41
io_uring/eventfd.c
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@ -47,6 +47,13 @@ static void io_eventfd_put(struct io_ev_fd *ev_fd)
call_rcu(&ev_fd->rcu, io_eventfd_free); call_rcu(&ev_fd->rcu, io_eventfd_free);
} }
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.
*/ */
@ -74,14 +81,18 @@ static bool io_eventfd_trigger(struct io_ev_fd *ev_fd)
return false; return false;
} }
void io_eventfd_signal(struct io_ring_ctx *ctx) /*
* On success, returns with an ev_fd reference grabbed and the RCU read
* lock held.
*/
static struct io_ev_fd *io_eventfd_grab(struct io_ring_ctx *ctx)
{ {
struct io_ev_fd *ev_fd = NULL; struct io_ev_fd *ev_fd;
if (READ_ONCE(ctx->rings->cq_flags) & IORING_CQ_EVENTFD_DISABLED) if (READ_ONCE(ctx->rings->cq_flags) & IORING_CQ_EVENTFD_DISABLED)
return; return NULL;
guard(rcu)(); 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
@ -90,16 +101,24 @@ void io_eventfd_signal(struct io_ring_ctx *ctx)
ev_fd = rcu_dereference(ctx->io_ev_fd); ev_fd = rcu_dereference(ctx->io_ev_fd);
/* /*
* Check again if ev_fd exists incase an io_eventfd_unregister call * Check again if ev_fd exists in case an io_eventfd_unregister call
* completed between the NULL check of ctx->io_ev_fd at the start of * completed between the NULL check of ctx->io_ev_fd at the start of
* the function and rcu_read_lock. * the function and rcu_read_lock.
*/ */
if (!io_eventfd_trigger(ev_fd)) if (io_eventfd_trigger(ev_fd) && refcount_inc_not_zero(&ev_fd->refs))
return; return ev_fd;
if (!refcount_inc_not_zero(&ev_fd->refs))
return; rcu_read_unlock();
if (__io_eventfd_signal(ev_fd)) return NULL;
io_eventfd_put(ev_fd); }
void io_eventfd_signal(struct io_ring_ctx *ctx)
{
struct io_ev_fd *ev_fd;
ev_fd = io_eventfd_grab(ctx);
if (ev_fd)
io_eventfd_release(ev_fd, __io_eventfd_signal(ev_fd));
} }
void io_eventfd_flush_signal(struct io_ring_ctx *ctx) void io_eventfd_flush_signal(struct io_ring_ctx *ctx)