TSLEEP(9) | Kernel Developer's Manual | TSLEEP(9) |
tsleep
, msleep
,
rwsleep
, wakeup
,
wakeup_n
, wakeup_one
— process context sleep and wakeup
#include
<sys/param.h>
#include <sys/systm.h>
int
tsleep
(void
*ident, int
priority, const char
*wmesg, int
timo);
int
msleep
(void
*ident, struct mutex
*mtx, int priority,
const char *wmesg,
int timo);
int
rwsleep
(void
*ident, struct rwlock
*wl, int priority,
const char *wmesg,
int timo);
void
wakeup
(void
*ident);
void
wakeup_n
(void
*ident, int
count);
void
wakeup_one
(void
*ident);
These functions implement voluntary context switching.
tsleep
(),
msleep
() and rwsleep
() are
used throughout the kernel whenever processing in the current context cannot
continue for any of the following reasons:
The
wakeup
(),
wakeup_n
(), and wakeup_one
()
functions are used to notify sleeping processes of possible changes to the
condition that caused them to go to sleep. Typically, an awakened process
will -- after it has acquired a context again -- retry the action that
blocked its operation to see if the “blocking” condition has
cleared.
The
tsleep
()
function takes the following arguments:
wakeup
() to get the process going again.
ident should not be
NULL
.PCATCH
is OR'ed into
priority the process checks for posted signals
before and after sleeping.p_wmesg
) for
user level utilities such as
ps(1).timo/hz
seconds. If this amount of time elapses
and no wakeup
(ident) has
occurred, and no signal (if PCATCH
was set) was posted,
tsleep
() will return
EWOULDBLOCK
.The
msleep
()
function behaves just like tsleep
(), but takes an
additional argument:
PNORELOCK
flag is set in the
priority argument.The
rwsleep
()
function behaves just like tsleep
(), but takes an
additional argument:
PNORELOCK
flag is set in the
priority argument.The
wakeup
()
function will mark all processes which are currently sleeping on the
identifier ident as runnable. Eventually, each of the
processes will resume execution in the kernel context, causing a return from
tsleep
(). Note that processes returning from sleep
should always re-evaluate the conditions that blocked them, since a call to
wakeup
() merely signals a
possible
change to the blocking conditions. For example, when two or more processes
are waiting for an exclusive lock, only one of them will succeed in
acquiring the lock when it is released. All others will have to go back to
sleep and wait for the next opportunity.
The
wakeup_n
()
and
wakeup_one
()
functions behave similarly to wakeup
() except that
only count or one process, respectively, is marked
runnable.
tsleep
(), msleep
()
and rwsleep
() return 0 if they return as a result of
a wakeup
(). If they return as a result of a signal,
the return value is ERESTART
if the signal has the
SA_RESTART
property (see
sigaction(2)), and
EINTR
otherwise. If they return as a result of a
timeout, the return value is EWOULDBLOCK
.
These functions are implemented in the file sys/kern/kern_synch.c.
September 13, 2016 | OpenBSD-6.1 |