unix_master(9r)unix_master(9r)NAMEunix_master - General: Forces execution onto the master CPU
SYNOPSIS
void unix_master(
void );
ARGUMENTS
None
DESCRIPTION
The unix_master routine forces execution of the kernel thread onto the
master CPU (also called the boot CPU). In other words, unix_master
binds the kernel thread to the master CPU. To release the kernel thread
from the bind to the master CPU, call the unix_release routine. You can
make recursive calls to unix_master as long as you make an equal number
of calls to unix_release.
The unix_master routine provides another way besides the simple and
complex lock routines to make a kernel module symmetric multiprocessing
(SMP) safe. Although calling unix_master is not optimal for performance
on an SMP CPU, it does provide third-party kernel module writers with
an easy way to make their modules SMP safe without using the lock rou‐
tines.
NOTES
Device drivers should not directly call the unix_master and
unix_release routines. One exception to this recommendation is when you
want a device driver's kernel threads to run only on the master CPU.
This situation occurs when your driver creates and starts its own ker‐
nel threads and you set the d_funnel member of the associated dsent
structure to the value DEV_FUNNEL. In this case, each kernel thread
must call unix_master once to ensure that the kernel thread runs only
on the master CPU. Remember to make a corresponding call to
unix_release.
CAUTIONS
To avoid deadlock, do not call the unix_master routine under the fol‐
lowing circumstances: When holding a simple lock In the driver's inter‐
rupt service routine
RETURN VALUES
None
SEE ALSO
routines: unix_release(9r)unix_master(9r)
