sleep on a synchronization variable
bool_t SV_WAIT_SIG(sv_t *svp, int priority,
causes the calling process to block
(the caller's execution is suspended
and other processes may be scheduled)
waiting for a call to
for the synchronization
variable specified by svp.
Pointer to the synchronization variable on which to sleep.
A hint to the scheduling policy as to the relative priority the caller
wishes to be assigned while running in the kernel
after waking up.
Pointer to a basic lock that must be locked
when SV_WAIT_SIG is called.
The basic lock is released
when the calling process blocks,
as described below.
returns TRUE (a non-zero value)
if the caller woke up because of a call to
or if the caller was
stopped and subsequently continued.
returns FALSE (zero)
if the caller woke up and returned early
because of a signal other than a job control stop signal,
or by a job control stop signal that did not result in
the caller stopping because the signal had a non-default disposition.
Valid values for priority are:
Priority appropriate for disk driver.
Priority appropriate for network driver.
Priority appropriate for terminal driver.
Priority appropriate for tape driver.
Drivers may use these values
to request a priority appropriate to a given type of device
or to request a priority that is high, medium or low
relative to other activities within the kernel.
It is also permissible to specify positive or negative offsets
from the values defined above.
Positive offsets result in more favorable priority.
The maximum allowable offset in all cases is 3
(that is, pridisk+3 and pridisk-3
are valid values
but pridisk+4 and pridisk-4
are not valid).
Offsets can be useful in defining
the relative importance of different locks or resources
that may be held by a given driver.
In general, a higher relative priority
should be used when the caller is blocked
while waiting for a highly contended kernel resource,
or when the caller is already holding one or more locks
or kernel resources upon entry to SV_WAIT_SIG.
The exact semantic of the priority argument
is specific to the scheduling class of the caller,
and some scheduling classes may choose to ignore the argument
for the purposes of assigning a scheduling priority.
The basic lock specified by lkp must be held upon entry.
The lock is released and the interrupt
priority level is set to plbase (block no interrupts)
after the process is queued on the synchronization variable but prior
to context switching to another process.
When the caller returns from SV_WAIT_SIG,
the basic lock is not held
and the interrupt priority level is equal to plbase.
may be interrupted by a signal,
in which case it returns early
without waiting for a call to
If the function is interrupted by a job control stop signal
(e.g. SIGSTOP, SIGTSTP,
which results in the caller entering a stopped state,
when continued, the SV_WAIT_SIG function
will return TRUE
as if the process had been awakened by a call to
If the function is interrupted by a signal
other than a job control stop signal,
or by a job control stop signal
that does not result in the caller stopping
(because the signal has a non-default disposition),
the SV_WAIT_SIG call returns FALSE.
must be able to tolerate premature wakeups.
After it is awakened (unblocked),
the code must reexamine the condition
on which it was blocked.
Context and synchronization
User or blockable
5, 5mp, 6, 6mp, 7, 7mp, 7.1, 7.1mp, 8, 8mp
``Synchronization variables'' in HDK Technical Reference
19 June 2005
© 2005 The SCO Group, Inc. All rights reserved.
OpenServer 6 and UnixWare (SVR5) HDK - June 2005