The eventfd code was written by me, rdivacky@ copyrigth applicable only
to epoll part of the Linuxulator code. Roman is ok to retire his copyright
from sys/kern/sys_eventfd.c and 'All rights reserved.' lines from
sys/compat/linux/linux_event.[c|h] and sys/kern/sys_eventfd.c files.
Reviewed by: kib, emaste
Approved by: rdivacky
Differential Revision: https://reviews.freebsd.org/D30677
MFC after: 2 weeks
eventfd is a Linux system call that produces special file descriptors
for event notification. When porting Linux software, it is currently
usually emulated by epoll-shim on top of kqueues. Unfortunately, kqueues
are not passable between processes. And, as noted by the author of
epoll-shim, even if they were, the library state would also have to be
passed somehow. This came up when debugging strange HW video decode
failures in Firefox. A native implementation would avoid these problems
and help with porting Linux software.
Since we now already have an eventfd implementation in the kernel (for
the Linuxulator), it's pretty easy to expose it natively, which is what
this patch does.
Submitted by: greg@unrelenting.technology
Reviewed by: markj (previous version)
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D26668
