<s>
In	O
real-time	B-General_Concept
computing	I-General_Concept
,	O
the	O
priority	B-Operating_System
ceiling	I-Operating_System
protocol	I-Operating_System
is	O
a	O
synchronization	O
protocol	O
for	O
shared	O
resources	O
to	O
avoid	O
unbounded	O
priority	B-Operating_System
inversion	I-Operating_System
and	O
mutual	O
deadlock	B-Operating_System
due	O
to	O
wrong	O
nesting	O
of	O
critical	B-Operating_System
sections	I-Operating_System
.	O
</s>
<s>
In	O
this	O
protocol	O
each	O
resource	O
is	O
assigned	O
a	O
priority	B-Operating_System
ceiling	I-Operating_System
,	O
which	O
is	O
a	O
priority	O
equal	O
to	O
the	O
highest	O
priority	O
of	O
any	O
task	B-General_Concept
which	O
may	O
lock	O
the	O
resource	O
.	O
</s>
<s>
The	O
protocol	O
works	O
by	O
temporarily	O
raising	O
the	O
priorities	O
of	O
tasks	O
in	O
certain	O
situations	O
,	O
thus	O
it	O
requires	O
a	O
scheduler	O
that	O
supports	O
dynamic	B-Algorithm
priority	I-Algorithm
scheduling	I-Algorithm
.	O
</s>
<s>
In	O
OCPP	O
,	O
a	O
task	B-General_Concept
X	O
's	O
priority	O
is	O
raised	O
when	O
a	O
higher-priority	O
task	B-General_Concept
Y	O
tries	O
to	O
acquire	O
a	O
resource	O
that	O
X	O
has	O
locked	O
.	O
</s>
<s>
The	O
task	B-General_Concept
's	O
priority	O
is	O
then	O
raised	O
to	O
the	O
priority	B-Operating_System
ceiling	I-Operating_System
of	O
the	O
resource	O
,	O
ensuring	O
that	O
task	B-General_Concept
X	O
quickly	O
finishes	O
its	O
critical	B-Operating_System
section	I-Operating_System
,	O
unlocking	O
the	O
resource	O
.	O
</s>
<s>
A	O
task	B-General_Concept
is	O
only	O
allowed	O
to	O
lock	O
a	O
resource	O
if	O
its	O
dynamic	O
priority	O
is	O
higher	O
than	O
the	O
priority	B-Operating_System
ceilings	I-Operating_System
of	O
all	O
resources	O
locked	O
by	O
other	O
tasks	O
.	O
</s>
<s>
Otherwise	O
the	O
task	B-General_Concept
becomes	O
blocked	O
,	O
waiting	O
for	O
the	O
resource	O
.	O
</s>
<s>
In	O
ICPP	O
,	O
a	O
task	B-General_Concept
's	O
priority	O
is	O
immediately	O
raised	O
when	O
it	O
locks	O
a	O
resource	O
.	O
</s>
<s>
The	O
task	B-General_Concept
's	O
priority	O
is	O
set	O
to	O
the	O
priority	B-Operating_System
ceiling	I-Operating_System
of	O
the	O
resource	O
,	O
thus	O
no	O
task	B-General_Concept
that	O
may	O
lock	O
the	O
resource	O
is	O
able	O
to	O
get	O
scheduled	O
.	O
</s>
<s>
This	O
ensures	O
the	O
OCPP	O
property	O
that	O
"	O
A	O
task	B-General_Concept
can	O
only	O
lock	O
a	O
resource	O
if	O
its	O
dynamic	O
priority	O
is	O
higher	O
than	O
the	O
priority	B-Operating_System
ceilings	I-Operating_System
of	O
all	O
resources	O
locked	O
by	O
other	O
tasks	O
"	O
.	O
</s>
<s>
ICPP	O
is	O
called	O
"	O
Ceiling	O
Locking	O
"	O
in	O
Ada	B-Language
,	O
"	O
Priority	O
Protect	O
Protocol	O
"	O
in	O
POSIX	O
and	O
"	O
Priority	B-Operating_System
Ceiling	I-Operating_System
Emulation	O
"	O
in	O
RTSJ	B-Language
.	O
</s>
