SVR5

pri(D5)

pri -- priority levels for sleep locks

Description

Priority levels are used with sleep locks to provide a hint for the relative priority to be assigned to the caller while running in the kernel after being wakened.

Usage

All entry points unconditionally acquiring a sleep lock permit the calling code to provide a pri specification. This is a hint for the relative priority the caller wishes to be assigned while running in the kernel after being unblocked.

NOTE: Note that the scheduler class-specific code is free to ignore this hint.

The base kernel can use the following symbols for specifying the priority. The list is ordered -- PRIMEM represents higher priority than PRINOD.

PRIMEM
PRINOD
PRIBIO
PRIMED
PRIPIPE
PRIVFS
PRIWAIT
PRIREMOTE
PRISLEP

For added flexibility, positive and negative offsets from these symbolic names are permitted, but the maximum allowable offset is 3.

WARNING: When converting from sleep(D3) to the sleep locks, note that the priority level values are reversed: for sleep locks, higher priority values indicate higher priority levels, whereas for sleep( ), lower priority values indicate higher priority levels.

The following global variables are defined to achieve a priority appropriate to a given type of driver or module interface.

pridisk: waiting in disk driver
prinet: waiting in network driver
pritty: waiting in terminal driver
pritape: waiting in tape driver

Alternatively, if the driver is only concerned about relative priorities, the following global variables are also available.

prihi
primed
prilo

For added flexibility, positive and negative offsets from the above priority values are permitted, but the maximum allowable offset is 3. Defining the priority values as global variables enhances the binary portability of the drivers. Furthermore, this scheme permits a given platform to assign priority values that are optimal for the platform. For instance, a disk-less machine may choose to assign a higher priority value to prinet compared to pridisk.

Hardware applicability

All

Version applicability

ddi: 5, 5mp, 6, 6mp, 7, 7mp, 7.1, 7.1mp, 8, 8mp