<s>
The	O
Native	B-Application
POSIX	I-Application
Thread	I-Application
Library	I-Application
(	O
NPTL	B-Application
)	O
is	O
an	O
implementation	O
of	O
the	O
POSIX	B-Operating_System
Threads	I-Operating_System
specification	O
for	O
the	O
Linux	B-Application
operating	I-Application
system	I-Application
.	O
</s>
<s>
Before	O
the	O
2.6	O
version	O
of	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
,	O
processes	O
were	O
the	O
schedulable	O
entities	O
,	O
and	O
there	O
were	O
no	O
special	O
facilities	O
for	O
threads	B-Operating_System
.	O
</s>
<s>
However	O
,	O
it	O
did	O
have	O
a	O
system	B-Operating_System
call	I-Operating_System
—	O
—	O
which	O
creates	O
a	O
copy	O
of	O
the	O
calling	O
process	O
where	O
the	O
copy	O
shares	O
the	O
address	O
space	O
of	O
the	O
caller	O
.	O
</s>
<s>
The	O
LinuxThreads	B-Operating_System
project	O
used	O
this	O
system	B-Operating_System
call	I-Operating_System
to	O
provide	O
kernel-level	O
threads	B-Operating_System
(	O
most	O
of	O
the	O
previous	O
thread	B-Operating_System
implementations	O
in	O
Linux	B-Operating_System
worked	O
entirely	O
in	O
userland	O
)	O
.	O
</s>
<s>
To	O
improve	O
upon	O
LinuxThreads	B-Operating_System
,	O
it	O
was	O
clear	O
that	O
some	O
kernel	B-Operating_System
support	O
and	O
a	O
new	O
threading	O
library	O
would	O
be	O
required	O
.	O
</s>
<s>
Two	O
competing	O
projects	O
were	O
started	O
to	O
address	O
the	O
requirement	O
:	O
NGPT	O
(	O
Next	O
Generation	O
POSIX	B-Operating_System
Threads	I-Operating_System
)	O
worked	O
on	O
by	O
a	O
team	O
which	O
included	O
developers	O
from	O
IBM	O
,	O
and	O
NPTL	B-Application
by	O
developers	O
at	O
Red	O
Hat	O
.	O
</s>
<s>
The	O
NGPT	O
team	O
collaborated	O
closely	O
with	O
the	O
NPTL	B-Application
team	O
and	O
combined	O
the	O
best	O
features	O
of	O
both	O
implementations	O
into	O
NPTL	B-Application
.	O
</s>
<s>
The	O
NGPT	O
project	O
was	O
subsequently	O
abandoned	O
in	O
mid-2003	O
after	O
merging	O
its	O
best	O
features	O
into	O
NPTL	B-Application
.	O
</s>
<s>
NPTL	B-Application
was	O
first	O
released	O
in	O
Red	O
Hat	O
Linux	B-Operating_System
9	O
.	O
</s>
<s>
Old-style	O
Linux	B-Operating_System
POSIX	O
threading	O
is	O
known	O
for	O
having	O
trouble	O
with	O
threads	B-Operating_System
that	O
refuse	O
to	O
yield	O
to	O
the	O
system	O
occasionally	O
,	O
because	O
it	O
does	O
not	O
take	O
the	O
opportunity	O
to	O
preempt	O
them	O
when	O
it	O
arises	O
,	O
something	O
that	O
Windows	O
was	O
known	O
to	O
do	O
better	O
at	O
the	O
time	O
.	O
</s>
<s>
Red	O
Hat	O
claimed	O
that	O
NPTL	B-Application
fixed	O
this	O
problem	O
in	O
an	O
article	O
on	O
the	O
Java	B-Language
website	O
about	O
Java	B-Language
on	O
Red	O
Hat	O
Linux	B-Operating_System
9	O
.	O
</s>
<s>
NPTL	B-Application
has	O
been	O
part	O
of	O
Red	O
Hat	O
Enterprise	O
Linux	B-Operating_System
since	O
version	O
3	O
,	O
and	O
in	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
since	O
version	O
2.6	O
.	O
</s>
<s>
It	O
is	O
now	O
a	O
fully	O
integrated	O
part	O
of	O
the	O
GNU	B-Language
C	I-Language
Library	I-Language
.	I-Language
</s>
<s>
There	O
exists	O
a	O
tracing	O
tool	O
for	O
NPTL	B-Application
,	O
called	O
(	O
)	O
.	O
</s>
<s>
And	O
an	O
(	O
)	O
was	O
written	O
for	O
testing	O
the	O
NPTL	B-Application
library	O
against	O
the	O
POSIX	O
standard	O
.	O
</s>
<s>
Like	O
LinuxThreads	B-Operating_System
,	O
NPTL	B-Application
is	O
a	O
1:1	O
threads	B-Operating_System
library	O
.	O
</s>
<s>
Threads	B-Operating_System
created	O
by	O
the	O
library	O
(	O
via	O
pthread_create	O
)	O
correspond	O
one-to-one	O
with	O
schedulable	O
entities	O
in	O
the	O
kernel	B-Operating_System
(	O
processes	O
,	O
in	O
the	O
Linux	B-Operating_System
case	O
)	O
.	O
</s>
<s>
New	O
threads	B-Operating_System
are	O
created	O
with	O
the	O
clone( )	O
system	B-Operating_System
call	I-Operating_System
called	O
through	O
the	O
NPTL	B-Application
library	O
.	O
</s>
<s>
NPTL	B-Application
relies	O
on	O
kernel	B-Operating_System
support	O
for	O
futexes	B-Application
to	O
more	O
efficiently	O
implement	O
user-space	O
locks	O
.	O
</s>
