diff options
| author | David Woodhouse <dwmw@amazon.co.uk> | 2020-10-27 16:55:21 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-09-19 13:20:06 +0300 |
| commit | 755e86f28ab9b85484567893aa5266e4e30a8fe9 (patch) | |
| tree | 6c85a1be1c6162558719269278dbca398fde6aab /fs/eventfd.c | |
| parent | 6b5d585e23022aa58fe494b16237c2a27efff58e (diff) | |
| download | linux-755e86f28ab9b85484567893aa5266e4e30a8fe9.tar.xz | |
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 <dwmw@amazon.co.uk>
Message-Id: <20201027135523.646811-2-dwmw2@infradead.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Stable-dep-of: 758b49204781 ("eventfd: prevent underflow for eventfd semaphores")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'fs/eventfd.c')
| -rw-r--r-- | fs/eventfd.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/fs/eventfd.c b/fs/eventfd.c index 4a14295cffe0..b8d38b970ce7 100644 --- a/fs/eventfd.c +++ b/fs/eventfd.c @@ -187,11 +187,14 @@ 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. |