From 28f1326710555bbe666f64452d08f2d7dd657cae Mon Sep 17 00:00:00 2001 From: David Woodhouse Date: Tue, 27 Oct 2020 13:55:21 +0000 Subject: eventfd: Export eventfd_ctx_do_read() Where events are consumed in the kernel, for example by KVM's irqfd_wakeup() and VFIO's virqfd_wakeup(), they currently lack a mechanism to drain the eventfd's counter. Since the wait queue is already locked while the wakeup functions are invoked, all they really need to do is call eventfd_ctx_do_read(). Add a check for the lock, and export it for them. Signed-off-by: David Woodhouse Message-Id: <20201027135523.646811-2-dwmw2@infradead.org> Signed-off-by: Paolo Bonzini --- fs/eventfd.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'fs/eventfd.c') diff --git a/fs/eventfd.c b/fs/eventfd.c index df466ef81ddd..e265b6dd4f34 100644 --- a/fs/eventfd.c +++ b/fs/eventfd.c @@ -182,11 +182,14 @@ static __poll_t eventfd_poll(struct file *file, poll_table *wait) return events; } -static void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __u64 *cnt) +void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __u64 *cnt) { + lockdep_assert_held(&ctx->wqh.lock); + *cnt = (ctx->flags & EFD_SEMAPHORE) ? 1 : ctx->count; ctx->count -= *cnt; } +EXPORT_SYMBOL_GPL(eventfd_ctx_do_read); /** * eventfd_ctx_remove_wait_queue - Read the current counter and removes wait queue. -- cgit v1.2.3