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/* litmus/pgm.c - common pgm control code
*/
#include <linux/sched.h>
#include <litmus/litmus.h>
#include <litmus/pgm.h>
#include <litmus/sched_trace.h>
/* Only readjust release/deadline if difference is over a given threshold.
It's a weak method for accounting overheads. Ideally, we'd know the last
time t was woken up by its last predecessor, rather than having to look
at 'now'. Adjustment threshold currently set to 200us. */
#define ADJUSTMENT_THRESH_NS (200*1000LL)
int setup_pgm_release(struct task_struct* t)
{
int shifted_release = 0;
/* approximate time last predecessor gave us tokens */
lt_t now = litmus_clock();
TRACE_TASK(t, "is starting a new PGM job: waiting:%d\n",
tsk_rt(t)->ctrl_page->pgm_waiting);
BUG_ON(!tsk_rt(t)->ctrl_page->pgm_waiting);
/* Adjust release time if we got the last tokens after release of this job.
This is possible since PGM jobs are early-released. Don't shift our
deadline if we got the tokens earlier than expected. */
if (now > tsk_rt(t)->job_params.release) {
long long diff_ns = now - tsk_rt(t)->job_params.release;
if (diff_ns > ADJUSTMENT_THRESH_NS) {
lt_t adj_deadline = now + get_rt_relative_deadline(t);
TRACE_TASK(t, "adjusting PGM release time from (r = %llu, d = %llu) "
"to (r = %llu, d = %llu)\n",
tsk_rt(t)->job_params.release, tsk_rt(t)->job_params.deadline,
now, adj_deadline);
tsk_rt(t)->job_params.release = now;
tsk_rt(t)->job_params.deadline = adj_deadline;
shifted_release = 1;
}
else {
TRACE_TASK(t, "adjustment falls below threshold. %lld < %lld\n",
diff_ns, ADJUSTMENT_THRESH_NS);
}
}
else {
TRACE_TASK(t, "got tokens early--no need to adjust release. "
"cur time = %llu, release time = %llu\n",
now, tsk_rt(t)->job_params.release);
}
/* possible that there can be multiple instances of pgm_release logged.
analysis tools should filter out all but the last pgm_release for
a given job release */
sched_trace_pgm_release(t);
return shifted_release;
}
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