From 755e86f28ab9b85484567893aa5266e4e30a8fe9 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() [ Upstream commit 28f1326710555bbe666f64452d08f2d7dd657cae ] 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 Stable-dep-of: 758b49204781 ("eventfd: prevent underflow for eventfd semaphores") Signed-off-by: Sasha Levin --- include/linux/eventfd.h | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'include') diff --git a/include/linux/eventfd.h b/include/linux/eventfd.h index 6cd2a92daf20..c1bd4883e2fa 100644 --- a/include/linux/eventfd.h +++ b/include/linux/eventfd.h @@ -42,6 +42,7 @@ __u64 eventfd_signal(struct eventfd_ctx *ctx, __u64 n); __u64 eventfd_signal_mask(struct eventfd_ctx *ctx, __u64 n, unsigned mask); int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx, wait_queue_entry_t *wait, __u64 *cnt); +void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __u64 *cnt); DECLARE_PER_CPU(int, eventfd_wake_count); @@ -89,6 +90,11 @@ static inline bool eventfd_signal_count(void) return false; } +static inline void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __u64 *cnt) +{ + +} + #endif #endif /* _LINUX_EVENTFD_H */ -- cgit v1.2.3