Signed-off-by: NeilBrown <neilb@xxxxxxx> -- I noticed that this was missing so had a go at writing something. Is there / Should there be a section 7 man page describing suspend and autosuspend and wakelocks etc?? Comments (of course) welcome. NeilBrown diff --git a/man2/epoll_ctl.2 b/man2/epoll_ctl.2 index 1fbe74eeea4e..6388f19195f1 100644 --- a/man2/epoll_ctl.2 +++ b/man2/epoll_ctl.2 @@ -154,6 +154,26 @@ The user must call with .B EPOLL_CTL_MOD to rearm the file descriptor with a new event mask. +.TP +.BR EPOLLWAKEUP " (since Linux 3.5)" +If +.B EPOLLONESHOT +and +.B EPOLLET +are clear and the process has the +.B CAP_BLOCK_SUSPEND +.BR capability (7), +ensure that the system does not enter "suspend" or +"hibernate" while this event is pending or being processed. +The event is considered as being "processed" from when it returned by +a call to +.BR epoll_wait (2) +until the next call to +.BR epoll_wait (2) +on the same +.BR epoll (7) +file descriptor. +.\" commit 4d7e30d98939a0340022ccd49325a3d70f7e0238 .SH RETURN VALUE When successful, .BR epoll_ctl () diff --git a/man7/epoll.7 b/man7/epoll.7 index a372d9727978..31b1a8c8c9ba 100644 --- a/man7/epoll.7 +++ b/man7/epoll.7 @@ -173,6 +173,35 @@ it is the caller's responsibility to rearm the file descriptor using .BR epoll_ctl (2) with .BR EPOLL_CTL_MOD . +.SS Interaction with autosleep +If the system is in +.B autosleep +mode via +.I /sys/power/autosleep +and an event happens which wakes the device from sleep, the device +driver will only keep the device awake until that event is queued. To +keep the device awake until the event has been processed it is +necessary to use +.B epoll +and the +.B EPOLLWAKEUP +flag. + +When this flag is set in the +.B events +field for a +.I struct epoll_event +then system will be kept awake from the moment the event is queued, +through the +.IR epoll_wait (2) +call which returns the event until the subsequent +.IR epoll_wait (2) +call. If the event should keep the system awake beyond that time, +the a separate +.I wake_lock +should be taken before the second +.IR epoll_wait (2) +call. .SS /proc interfaces The following interfaces can be used to limit the amount of kernel memory consumed by epoll:
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