selinit() and
seldestroy() functions must be used to initialize and destroy the
struct selinfo. The
seldestroy() function may block.
selrecord() and
selnotify() are used by device drivers to coordinate with the kernel implementation of
select(2) and
poll(2). Each object that can be polled contains a
selinfo record. Device drivers provide locking for the
selinfo record.
selrecord() records that the calling thread is interested in events related to a given object.
selrecord() should only be called when the poll routine determines that the object is not ready for I/O: there are no events of interest pending. The check for pending I/O and call to
selrecord() must be atomic. Atomicity can be provided by holding the object's lock across the test and call to
selrecord(). For non-MPSAFE drivers, the global
kernel_lock is enough to provide atomicity.
selnotify() is called by the underlying object handling code in order to notify any waiting threads that an event of interest has occurred. The same lock held across the poll method and call to
selrecord() must be held across the call to
selnotify(). The lock prevents an event of interest being signalled while a thread is in the process of recording its interest.
The
events indicates which event happen. Zero may be used if unknown.
selnotify() also calls
KNOTE() passing
knhint as an argument.