diff options
| author | David Woodhouse <dwmw@amazon.co.uk> | 2020-10-27 14:55:21 +0100 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2020-11-15 15:49:10 +0100 |
| commit | 28f1326710555bbe666f64452d08f2d7dd657cae (patch) | |
| tree | 0500d5c7ff66eda5051b0221b04c73b28c8d8942 /fs/eventfd.c | |
| parent | kvm/eventfd: Use priority waitqueue to catch events before userspace (diff) | |
| download | linux-28f1326710555bbe666f64452d08f2d7dd657cae.tar.xz linux-28f1326710555bbe666f64452d08f2d7dd657cae.zip | |
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 <dwmw@amazon.co.uk>
Message-Id: <20201027135523.646811-2-dwmw2@infradead.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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 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. |