1 files changed, 59 insertions, 22 deletions
diff --git a/lib/libc/sys/fcntl.2 b/lib/libc/sys/fcntl.2
index f53c02f..877e830 100644
--- a/lib/libc/sys/fcntl.2
+++ b/lib/libc/sys/fcntl.2
@@ -70,7 +70,7 @@ share the same file status flags).
 .It
 The close-on-exec flag associated with the new file descriptor
 is set to remain open across
-.Xr execv 2
+.Xr execve 2
 system calls.
 .El
 .It Dv F_GETFD
@@ -128,9 +128,9 @@ flags are as follows:
 .Bl -tag -width O_NONBLOCKX
 .It Dv O_NONBLOCK
 Non-blocking I/O; if no data is available to a
-.Xr read
+.Xr read 2
 call, or if a
-.Xr write
+.Xr write 2
 operation would block,
 the read or write call returns -1 with the error
 .Er EAGAIN .
@@ -170,7 +170,7 @@ taken as a pointer to a
 .Fa "struct flock"
 (see above).
 The information retrieved overwrites the information passed to
-.Nm fcntl
+.Fn fcntl
 in the
 .Fa flock
 structure.
@@ -193,18 +193,18 @@ or exclusive (or write) locks,
 as well as remove either type of lock
 .Dv (F_UNLCK) .
 If a shared or exclusive lock cannot be set,
-.Nm fcntl
+.Fn fcntl
 returns immediately with
-.Er EACCES .
+.Er EAGAIN .
 .It Dv F_SETLKW
 This command is the same as
 .Dv F_SETLK
 except that if a shared or exclusive lock is blocked by other locks,
 the process waits until the request can be satisfied.
 If a signal that is to be caught is received while
-.Nm fcntl
+.Fn fcntl
 is waiting for a region, the
-.Nm fcntl
+.Fn fcntl
 will be interrupted if the signal handler has not specified the
 .Dv SA_RESTART
 (see
@@ -290,15 +290,17 @@ locks conflicts with the type specified in the request.
 This interface follows the completely stupid semantics of System V and
 .St -p1003.1-88
 that require that all locks associated with a file for a given process are
-removed when \fIany\fP file descriptor for that file is closed by that process.
+removed when 
+.Em any
+file descriptor for that file is closed by that process.
 This semantic means that applications must be aware of any files that
 a subroutine library may access.
 For example if an application for updating the password file locks the
 password file database while making the update, and then calls
-.Xr getpwname 3
+.Xr getpwnam 3
 to retrieve a record,
 the lock will be lost because 
-.Xr getpwname 3
+.Xr getpwnam 3
 opens, reads, and closes the password database.
 The database close will release all locks that the process has
 associated with the database, even if the library routine never
@@ -330,6 +332,29 @@ This implementation detects that sleeping until a locked region is unlocked
 would cause a deadlock and fails with an
 .Er EDEADLK
 error.
+.Sh IMPLEMENTATION NOTES
+.Pp
+In the non-threaded library
+.Fn fcntl
+is implemented as the
+.Va fcntl
+syscall.
+.Pp
+In the threaded library, the
+.Va fcntl
+syscall is assembled to
+.Fn _thread_sys_fcntl
+and
+.Fn fcntl
+is implemented as a function which disables thread rescheduling, locks
+.Va fd
+for read and write, then calls
+.Fn _thread_sys_fcntl .
+Before returning,
+.Fn fcntl
+unlocks
+.Va fd
+and enables thread rescheduling.
 .Sh RETURN VALUES
 Upon successful completion, the value returned depends on
 .Fa cmd
@@ -354,9 +379,9 @@ is set to indicate the error.
 .Fn Fcntl
 will fail if:
 .Bl -tag -width Er
-.It Bq Er EACCES
+.It Bq Er EAGAIN
 The argument
-.Fa arg
+.Fa cmd
 is
 .Dv F_SETLK ,
 the type of lock
@@ -401,12 +426,6 @@ is an exclusive lock
 and
 .Fa fildes
 is not a valid file descriptor open for writing.
-.It Bq Er EMFILE
-.Fa Cmd
-is
-.Dv F_DUPFD
-and the maximum allowed number of file descriptors are currently
-open.
 .It Bq Er EDEADLK
 The argument
 .Fa cmd
@@ -445,7 +464,7 @@ refers to a file that does not support locking.
 The argument
 .Fa cmd
 is
-.Dv F_DUPED
+.Dv F_DUPFD
 and the maximum number of file descriptors permitted for the
 process are already in use,
 or no file descriptors greater than or equal to
@@ -467,15 +486,33 @@ is
 and
 the process ID given as argument is not in use.
 .El
+.Pp
+In addition, if 
+.Fa fd
+refers to a descriptor open on a terminal device (as opposed to a
+descriptor open on a socket), a
+.Fa cmd
+of
+.Dv F_SETOWN
+can fail for the same reasons as in
+.Xr tcsetpgrp 3 ,
+and a
+.Fa cmd
+of
+.Dv F_GETOWN
+for the reasons as stated in
+.Xr tcgetpgrp 3 .
 .Sh SEE ALSO
 .Xr close 2 ,
 .Xr execve 2 ,
 .Xr flock 2 ,
 .Xr getdtablesize 2 ,
 .Xr open 2 ,
-.Xr sigvec 2
+.Xr sigvec 2 ,
+.Xr tcgetpgrp 3 ,
+.Xr tcsetpgrp 3
 .Sh HISTORY
 The
-.Nm
+.Fn fcntl
 function call appeared in
 .Bx 4.2 .