<s>
In	O
computing	O
,	O
an	O
inter-processor	B-Device
interrupt	I-Device
(	O
IPI	O
)	O
,	O
also	O
known	O
as	O
a	O
shoulder	B-Device
tap	I-Device
,	O
is	O
a	O
special	O
type	O
of	O
interrupt	B-Application
by	O
which	O
one	O
processor	O
may	O
interrupt	B-Application
another	O
processor	O
in	O
a	O
multiprocessor	B-Operating_System
system	O
if	O
the	O
interrupting	B-Application
processor	O
requires	O
action	O
from	O
the	O
other	O
processor	O
.	O
</s>
<s>
flushes	O
of	O
memory	B-General_Concept
management	I-General_Concept
unit	I-General_Concept
caches	O
,	O
such	O
as	O
translation	B-Architecture
lookaside	I-Architecture
buffers	I-Architecture
,	O
on	O
other	O
processors	O
when	O
memory	O
mappings	O
are	O
changed	O
by	O
one	O
processor	O
;	O
</s>
<s>
The	O
M65MP	O
option	O
of	O
OS/360	B-Application
used	O
the	O
Direct	O
Control	O
feature	O
of	O
the	O
S/360	B-Application
to	O
generate	O
an	O
interrupt	B-Application
on	O
another	O
processor	O
;	O
on	O
S/370	B-Device
and	O
its	O
successors	O
,	O
including	O
z/Architecture	B-Device
,	O
the	O
SIGNAL	O
PROCESSOR	O
instruction	O
provides	O
a	O
more	O
formalized	O
interface	O
.	O
</s>
<s>
The	O
documentation	O
for	O
some	O
IBM	O
operating	O
systems	O
refers	O
to	O
this	O
as	O
a	O
shoulder	B-Device
tap	I-Device
.	O
</s>
<s>
On	O
IBM	O
PC	O
compatible	O
computers	O
that	O
use	O
the	O
Advanced	B-Device
Programmable	I-Device
Interrupt	I-Device
Controller	I-Device
(	O
APIC	O
)	O
,	O
IPI	O
signaling	O
is	O
often	O
performed	O
using	O
the	O
APIC	O
.	O
</s>
<s>
When	O
a	O
CPU	O
wishes	O
to	O
send	O
an	O
interrupt	B-Application
to	O
another	O
CPU	O
,	O
it	O
stores	O
the	O
interrupt	B-General_Concept
vector	I-General_Concept
and	O
the	O
identifier	O
of	O
the	O
target	O
's	O
local	B-Device
APIC	I-Device
in	O
the	O
Interrupt	B-Application
Command	O
Register	O
(	O
ICR	O
)	O
of	O
its	O
own	O
local	B-Device
APIC	I-Device
.	O
</s>
<s>
A	O
message	O
is	O
then	O
sent	O
via	O
the	O
APIC	O
bus	O
to	O
the	O
target	O
's	O
local	B-Device
APIC	I-Device
,	O
which	O
therefore	O
issues	O
a	O
corresponding	O
interrupt	B-Application
to	O
its	O
own	O
CPU	O
.	O
</s>
<s>
In	O
a	O
multiprocessor	B-Operating_System
system	O
running	O
Microsoft	B-Application
Windows	I-Application
,	O
a	O
processor	O
may	O
interrupt	B-Application
another	O
processor	O
for	O
the	O
following	O
reasons	O
,	O
in	O
addition	O
to	O
the	O
ones	O
listed	O
above	O
:	O
</s>
<s>
queue	O
a	O
DISPATCH_LEVEL	O
interrupt	B-Application
to	O
schedule	O
a	O
particular	O
thread	O
for	O
execution	O
;	O
</s>
