.BI "long syscall(SYS_futex, uint32_t *" uaddr ", FUTEX_FD, uint32_t " val );
.fi
.SH DESCRIPTION
-.TP
-.BR FUTEX_FD " (from Linux 2.6.0 up to and including Linux 2.6.25)"
-.\" Strictly speaking, from Linux 2.5.x to Linux 2.6.25
This operation creates a file descriptor that is associated with
the futex at
.IR uaddr .
The caller must close the returned file descriptor after use.
+.P
When another process or thread performs a
.BR FUTEX_WAKE (2const)
on the futex word, the file descriptor indicates as being readable with
.BR poll (2),
and
.BR epoll (7)
-.IP
+.P
The file descriptor can be used to obtain asynchronous notifications: if
.I val
is nonzero, then, when another process or thread executes a
Linux.
.SH HISTORY
From Linux 2.6.0 up to and including Linux 2.6.25.
+.\" Strictly speaking, from Linux 2.5.x to Linux 2.6.25
.P
Because it was inherently racy,
.B FUTEX_FD