On Mon, 02 May 2005 10:57:29 +0530
"Arun Srinivas" <[email protected]> wrote:
> 1) From main(i.e., parent) create a shared memory seg. using shmget() and
> shmat(). This is for communication between parent and child. I am trying to
> use this as a locking mechanism to make them tightly coupled so that one
> does not race before the other.
> 2) create child by fork() and call shmat() to attach this segment to child
> too
> 3) In parent and child call ioctl() to pass their PID's from user space to
> kernel space...so that I can measure when the particular PID's are scheduled
> in the scheduler
>
> I suppose shmget() dosent use a system call.So still confused about the
> occasional resechedule behavior.
You might try the user triggered tracing which is available with Ingo's
realtime preemption patches.
Enable the latency tracing in the kernel confgig and
echo 1 > /proc/sys/kernel/user_triggered_tracing
then in your code you want to be checked do this before the section:
gettimeofday (1, 1)
and
gettimeofday (1, 0)
after the section you want to be checked.. Every reschedule of the task
will result in a signal SIGUSR2 sent to your program and a latency trace
in the syslog..
..i think
Flo
--
Palimm Palimm!
http://affenbande.org/~tapas/
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