<s>
In	O
the	O
Linux	B-Application
operating	I-Application
system	I-Application
,	O
LinuxThreads	B-Operating_System
was	O
a	O
partial	O
implementation	O
of	O
POSIX	B-Operating_System
Threads	I-Operating_System
introduced	O
in	O
1996	O
.	O
</s>
<s>
The	O
main	O
developer	O
of	O
LinuxThreads	B-Operating_System
was	O
Xavier	O
Leroy	O
.	O
</s>
<s>
It	O
has	O
been	O
superseded	O
by	O
the	O
Native	B-Application
POSIX	I-Application
Thread	I-Application
Library	I-Application
(	O
NPTL	B-Application
)	O
.	O
</s>
<s>
LinuxThreads	B-Operating_System
had	O
a	O
number	O
of	O
problems	O
,	O
mainly	O
owing	O
to	O
the	O
implementation	O
,	O
which	O
used	O
the	O
clone	O
system	O
call	O
to	O
create	O
a	O
new	O
process	B-Operating_System
sharing	O
the	O
parent	O
's	O
address	B-General_Concept
space	I-General_Concept
.	O
</s>
<s>
For	O
example	O
,	O
threads	O
had	O
distinct	O
process	B-Operating_System
identifiers	I-Operating_System
,	O
causing	O
problems	O
for	O
signal	B-Operating_System
handling	I-Operating_System
;	O
LinuxThreads	B-Operating_System
used	O
the	O
signals	O
SIGUSR1	B-General_Concept
and	O
SIGUSR2	B-General_Concept
for	O
inter-thread	O
coordination	O
,	O
meaning	O
these	O
signals	O
could	O
not	O
be	O
used	O
by	O
programs	O
.	O
</s>
<s>
To	O
improve	O
the	O
situation	O
,	O
two	O
competing	O
projects	O
were	O
started	O
to	O
develop	O
a	O
replacement	O
;	O
NGPT	O
(	O
Next	O
Generation	O
POSIX	B-Operating_System
Threads	I-Operating_System
)	O
and	O
NPTL	B-Application
.	O
</s>
<s>
NPTL	B-Application
won	O
out	O
and	O
is	O
today	O
shipped	O
with	O
the	O
vast	O
majority	O
of	O
Linux	B-Operating_System
systems	O
.	O
</s>
<s>
,	O
LinuxThreads	B-Operating_System
may	O
still	O
be	O
seen	O
on	O
production	O
systems	O
,	O
particularly	O
those	O
using	O
version	O
2.4	O
or	O
lower	O
of	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
,	O
as	O
NPTL	B-Application
requires	O
facilities	O
which	O
were	O
specifically	O
added	O
into	O
the	O
2.6	O
version	O
of	O
the	O
kernel	B-Operating_System
for	O
its	O
use	O
.	O
</s>
<s>
LinuxThreads	B-Operating_System
was	O
also	O
ported	O
to	O
and	O
used	O
on	O
FreeBSD	O
.	O
</s>
