Fix a file descriptor close race in kqueue_register()

After inserting a knote, check that the associated file descriptor
still references the same file. Remove the knote if the descriptor
has changed because otherwise the kqueue becomes inconsistent with
the file descriptor table.

There is an analogous race in fcntl(F_SETLK). It is already handled,
but the code can be simplified by using the same check as in
kqueue_register().

Fix inspired by DragonFly BSD

OK mpi@, anton@

Document fd_getfile_mode(9).

OK mpi@

Document locking with fdrelease().

Update the manual to match with the current semantics of fd_getfile().
Also, adjust the notes about FREF() and FRELE() as proper reference
counting is becoming mandatory.

OK jmc@, mpi@

tweak previous;

Add a flags argument to falloc() that lets it optionally set the
close-on-exec flag on the newly allocated fd. Make falloc()'s
return arguments non-optional: assert that they're not NULL.

ok mpi@ millert@

add missing NAME entries;
feedback/ok schwarze

Pass a thread pointer instead of its file descriptor table to getvnode(9).

Input and ok millert@

Pass a thread pointer instead of its file descriptor table to getsock(9).

Diff from Vitaliy Makkoveev.

Manpage tweak and ok millert@

FRELE returns an int not void. It is actually the return value
of fdrop() (or 0 if the ref count is non-zero). From Kanonenvogel

Replace old-fashioned .Fd by new-fangled .In for #include lines.
Diff from Jan Klemkow <j dot klemkow at wemelug dot de> on tech@.
No objection from jmc@ against this type of change.

FRELE() has a second argument now

convert to new .Dd format;

put "CODE REFERENCES" before "SEE ALSO" for consistency

ok jmc@

getvnode requires vnode.h; from bret lambert
ok pedro

make .Nm match .Dt to avoid screwy apropos(1) output;
found by pb@

typo from Jared Yanovich;

typos;

VOP, crypto and disklabel ok tedu@
audio(9) ok naddy@

Document the FREF done in getvnode and soon in getsock.

o) fix .Sh usage;
o) minor fix;

art@ ok

o) fix .Xr usage;
o) typos;

art@ ok

Document various file descriptor access functoins in the kernel.

Document fd_getfile_mode(9).

OK mpi@

Document locking with fdrelease().

Update the manual to match with the current semantics of fd_getfile().
Also, adjust the notes about FREF() and FRELE() as proper reference
counting is becoming mandatory.

OK jmc@, mpi@

tweak previous;

Add a flags argument to falloc() that lets it optionally set the
close-on-exec flag on the newly allocated fd. Make falloc()'s
return arguments non-optional: assert that they're not NULL.

ok mpi@ millert@

add missing NAME entries;
feedback/ok schwarze

Pass a thread pointer instead of its file descriptor table to getvnode(9).

Input and ok millert@

Pass a thread pointer instead of its file descriptor table to getsock(9).

Diff from Vitaliy Makkoveev.

Manpage tweak and ok millert@

FRELE returns an int not void. It is actually the return value
of fdrop() (or 0 if the ref count is non-zero). From Kanonenvogel

Replace old-fashioned .Fd by new-fangled .In for #include lines.
Diff from Jan Klemkow <j dot klemkow at wemelug dot de> on tech@.
No objection from jmc@ against this type of change.

FRELE() has a second argument now

convert to new .Dd format;

put "CODE REFERENCES" before "SEE ALSO" for consistency

ok jmc@

getvnode requires vnode.h; from bret lambert
ok pedro

make .Nm match .Dt to avoid screwy apropos(1) output;
found by pb@

typo from Jared Yanovich;

typos;

VOP, crypto and disklabel ok tedu@
audio(9) ok naddy@

Document the FREF done in getvnode and soon in getsock.

o) fix .Sh usage;
o) minor fix;

art@ ok

o) fix .Xr usage;
o) typos;

art@ ok

Document various file descriptor access functoins in the kernel.

Document locking with fdrelease().

Update the manual to match with the current semantics of fd_getfile().
Also, adjust the notes about FREF() and FRELE() as proper reference
counting is becoming mandatory.

OK jmc@, mpi@

tweak previous;

Add a flags argument to falloc() that lets it optionally set the
close-on-exec flag on the newly allocated fd. Make falloc()'s
return arguments non-optional: assert that they're not NULL.

ok mpi@ millert@

add missing NAME entries;
feedback/ok schwarze

Pass a thread pointer instead of its file descriptor table to getvnode(9).

Input and ok millert@

Pass a thread pointer instead of its file descriptor table to getsock(9).

Diff from Vitaliy Makkoveev.

Manpage tweak and ok millert@

FRELE returns an int not void. It is actually the return value
of fdrop() (or 0 if the ref count is non-zero). From Kanonenvogel

Replace old-fashioned .Fd by new-fangled .In for #include lines.
Diff from Jan Klemkow <j dot klemkow at wemelug dot de> on tech@.
No objection from jmc@ against this type of change.

FRELE() has a second argument now

convert to new .Dd format;

put "CODE REFERENCES" before "SEE ALSO" for consistency

ok jmc@

getvnode requires vnode.h; from bret lambert
ok pedro

make .Nm match .Dt to avoid screwy apropos(1) output;
found by pb@

typo from Jared Yanovich;

typos;

VOP, crypto and disklabel ok tedu@
audio(9) ok naddy@

Document the FREF done in getvnode and soon in getsock.

o) fix .Sh usage;
o) minor fix;

art@ ok

o) fix .Xr usage;
o) typos;

art@ ok

Document various file descriptor access functoins in the kernel.

Update the manual to match with the current semantics of fd_getfile().
Also, adjust the notes about FREF() and FRELE() as proper reference
counting is becoming mandatory.

OK jmc@, mpi@

tweak previous;

Add a flags argument to falloc() that lets it optionally set the
close-on-exec flag on the newly allocated fd. Make falloc()'s
return arguments non-optional: assert that they're not NULL.

ok mpi@ millert@

add missing NAME entries;
feedback/ok schwarze

Pass a thread pointer instead of its file descriptor table to getvnode(9).

Input and ok millert@

Pass a thread pointer instead of its file descriptor table to getsock(9).

Diff from Vitaliy Makkoveev.

Manpage tweak and ok millert@

FRELE returns an int not void. It is actually the return value
of fdrop() (or 0 if the ref count is non-zero). From Kanonenvogel

Replace old-fashioned .Fd by new-fangled .In for #include lines.
Diff from Jan Klemkow <j dot klemkow at wemelug dot de> on tech@.
No objection from jmc@ against this type of change.

FRELE() has a second argument now

convert to new .Dd format;

put "CODE REFERENCES" before "SEE ALSO" for consistency

ok jmc@

getvnode requires vnode.h; from bret lambert
ok pedro

make .Nm match .Dt to avoid screwy apropos(1) output;
found by pb@

typo from Jared Yanovich;

typos;

VOP, crypto and disklabel ok tedu@
audio(9) ok naddy@

Document the FREF done in getvnode and soon in getsock.

o) fix .Sh usage;
o) minor fix;

art@ ok

o) fix .Xr usage;
o) typos;

art@ ok

Document various file descriptor access functoins in the kernel.

tweak previous;

Add a flags argument to falloc() that lets it optionally set the
close-on-exec flag on the newly allocated fd. Make falloc()'s
return arguments non-optional: assert that they're not NULL.

ok mpi@ millert@

add missing NAME entries;
feedback/ok schwarze

Pass a thread pointer instead of its file descriptor table to getvnode(9).

Input and ok millert@

Pass a thread pointer instead of its file descriptor table to getsock(9).

Diff from Vitaliy Makkoveev.

Manpage tweak and ok millert@

FRELE returns an int not void. It is actually the return value
of fdrop() (or 0 if the ref count is non-zero). From Kanonenvogel

Replace old-fashioned .Fd by new-fangled .In for #include lines.
Diff from Jan Klemkow <j dot klemkow at wemelug dot de> on tech@.
No objection from jmc@ against this type of change.

FRELE() has a second argument now

convert to new .Dd format;

put "CODE REFERENCES" before "SEE ALSO" for consistency

ok jmc@

getvnode requires vnode.h; from bret lambert
ok pedro

make .Nm match .Dt to avoid screwy apropos(1) output;
found by pb@

typo from Jared Yanovich;

typos;

VOP, crypto and disklabel ok tedu@
audio(9) ok naddy@

Document the FREF done in getvnode and soon in getsock.

o) fix .Sh usage;
o) minor fix;

art@ ok

o) fix .Xr usage;
o) typos;

art@ ok

Document various file descriptor access functoins in the kernel.