07-21-2015
A timer. Hardware interrupts are happening all the time which gives a vector for the kernel to regain control without programs cooperatively giving it up. Keyboard or network (as just two examples) input being available cause interrupts so we can handle the data before buffers overflow. The timer does this too at regular intervals every few hz (Linux i386 once defaulted to 1000, MIPS to 100). I imagine that's when the scheduler decides who goes next. It's not just when fork() is called. we'd never regain control like that.
when there is no work to do, calling the interrupt handler alone keeps the CPU a little busy and wastes some power so modern kernels have dynamic ticks.
So the timer interrupt causes this context switch, how does it work depends on the arch I suppose. I know in MIPS there was a jump table of exception handlers created and stored at the beginning of memory. When the timer ticked, the Interrupt exception handler is called. That in turn checked a status register to know which interrupt. Then you'd exit that into the next program that deserved attention.
This User Gave Thanks to neutronscott For This Post:
9 More Discussions You Might Find Interesting
1. UNIX for Dummies Questions & Answers
the following unix command
ls | grep'?cw1' | wc -l
converting it to english is it going to be like
list the result of the search '?cw1' in number of lines
is that correct ? (4 Replies)
Discussion started by: props
4 Replies
2. UNIX for Dummies Questions & Answers
I am confused about what this line of code would do. I understand all the pieces but not the final outcome. Anyone that could help?
find / -type f -xdev -mtime 0 -size 100000 -exec ls -lht {} /; 2>/dev/null (4 Replies)
Discussion started by: NickNine
4 Replies
3. Solaris
Hi,
I am trying to take the Statistics of the machine during load.Can someone explian the parameters of
iostat:
tty sd1 sd2 sd3 sd4 cpu
tin tout kps tps serv kps tps serv kps tps serv kps tps serv us sy wt id
vmstat:
kthr ... (1 Reply)
Discussion started by: grrajeish
1 Replies
4. Shell Programming and Scripting
Some software, when you install it, prompts you for variables, such as the username for the software, or the password you are setting for the software's root account.
I would like to know if it is possible to do such a thing, and if yes, how?
basically, I would like my installer script to prompt... (3 Replies)
Discussion started by: Bakes
3 Replies
5. Shell Programming and Scripting
dear coders,
i need some inspiration again...
there is something what i always wanted to know... how to code following:
value 1: __________
value 2: __________
important: when my "script" starts the display has to be cleared and two lines are shown (see above), the cursor has to be... (2 Replies)
Discussion started by: pseudocoder
2 Replies
6. UNIX for Advanced & Expert Users
Hi all.
can you please tell me
(root) NOPASSWD: ALL
what this command means (1 Reply)
Discussion started by: mindtee_abhi
1 Replies
7. Solaris
What is openboot prompt
is this some kind of shell , and where is located :p (2 Replies)
Discussion started by: solaris_user
2 Replies
8. Shell Programming and Scripting
Hi Experts, we do have a shell script for Unix Solaris, which will kill all the process manullay, it used to work in my previous env, but now it is throwing this error.. could some one please help me to resolve it
This is how we execute the script (and this is the requirement) ... (2 Replies)
Discussion started by: jonnyvic
2 Replies
9. Shell Programming and Scripting
Hi everyone I'm new here and I don't know some command of unix, please help by describe me how it work, I study unix command by myself and can't search exactly means so...Thanks :D
sqlplus -s /nolog @${SQLFILE} ${file_type} >> ${OUTPUT_FILE}
date "+%Y%m%d%H%M%S"
$/usr/bin/echo "INFO : $1"... (2 Replies)
Discussion started by: zound617
2 Replies
LEARN ABOUT DEBIAN
ddi_intr_hilevel
ddi_intr_hilevel(9F) Kernel Functions for Drivers ddi_intr_hilevel(9F)
NAME
ddi_intr_hilevel - indicate interrupt handler type
SYNOPSIS
#include <sys/ddi.h>
#include <sys/sunddi.h>
int ddi_intr_hilevel(dev_info_t *dip, uint_t inumber);
INTERFACE LEVEL
Solaris DDI specific (Solaris DDI).
PARAMETERS
dip Pointer to dev_info structure.
inumber Interrupt number.
DESCRIPTION
ddi_intr_hilevel() returns non-zero if the specified interrupt is a "high level" interrupt.
High level interrupts must be handled without using system services that manipulate thread or process states, because these interrupts are
not blocked by the scheduler.
In addition, high level interrupt handlers must take care to do a minimum of work because they are not preemptable.
A typical high level interrupt handler would put data into a circular buffer and schedule a soft interrupt by calling ddi_trigger_soft-
intr(). The circular buffer could be protected by using a mutex that was properly initialized for the interrupt handler.
ddi_intr_hilevel() can be used before calling ddi_add_intr() to decide which type of interrupt handler should be used. Most device drivers
are designed with the knowledge that the devices they support will always generate low level interrupts, however some devices, for example
those using SBus or VME bus level 6 or 7 interrupts must use this test because on some machines those interrupts are high level (above the
scheduler level) and on other machines they are not.
RETURN VALUES
non-zero indicates a high-level interrupt.
CONTEXT
These functions can be called from user or interrupt context.
SEE ALSO
ddi_add_intr(9F), mutex(9F)
Writing Device Drivers
SunOS 5.10 7 Jan 1992 ddi_intr_hilevel(9F)