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SubjectRe: [PATCH 2/2] tracing, sched: Add a new tracepoint for sleeptime

>
> +#ifdef CREATE_TRACE_POINTS
> +static inline u64 trace_get_sleeptime(struct task_struct *tsk)
> +{
> +#ifdef CONFIG_SCHEDSTATS
> + u64 block, sleep;
> +
> + block = tsk->se.statistics.block_start;
> + sleep = tsk->se.statistics.sleep_start;
Arun, probably you have missed one of my comments.
block_start and sleep_start should be zeroized here.

tsk->se.statistics.block_start = 0;
tsk->se.statistics.sleep_start = 0;

The following program provokes this problem:

#include<unistd.h>
#include<time.h>
#include<sys/select.h>

int main()
{
struct timespec ts1;
struct timeval tv1;
int i;
long s;


for (i = 0; i< 1000; i++) {
ts1.tv_sec = 0;
ts1.tv_nsec = 1000000;
nanosleep(&ts1, NULL);

tv1.tv_sec = 0;
tv1.tv_usec = 4000;
select(0, NULL, NULL, NULL,&tv1);
if (i % 100 == 0) {
s = time(NULL);
while (time(NULL) - s < 4);
}
}
return 1;
}

> +
> + return block ? block : sleep ? sleep : 0;
> +#else
> + return 0;
> +#endif
> +}
> +#endif
> +
> +/*
> + * Tracepoint for accounting sleeptime (time the task is sleeping
> + * or waiting for I/O).
> + */
> +TRACE_EVENT(sched_stat_sleeptime,
> +
> + TP_PROTO(struct task_struct *tsk, u64 now),
> +
> + TP_ARGS(tsk, now),
> +
> + TP_STRUCT__entry(
> + __array( char, comm, TASK_COMM_LEN )
> + __field( pid_t, pid )
> + __field( u64, sleeptime )
> + ),
> +
> + TP_fast_assign(
> + memcpy(__entry->comm, tsk->comm, TASK_COMM_LEN);
> + __entry->pid = tsk->pid;
> + __entry->sleeptime = trace_get_sleeptime(tsk);
> + __entry->sleeptime = __entry->sleeptime ?
> + now - __entry->sleeptime : 0;
> + )
> + TP_perf_assign(
> + __perf_count(__entry->sleeptime);
> + ),
> +
> + TP_printk("comm=%s pid=%d sleeptime=%Lu [ns]",
> + __entry->comm, __entry->pid,
> + (unsigned long long)__entry->sleeptime)
> +);
> +
> /*
> * Tracepoint for showing priority inheritance modifying a tasks
> * priority.
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index ca8fd44..172e6ee 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1899,6 +1899,7 @@ static void finish_task_switch(struct rq *rq, struct task_struct *prev)
> local_irq_enable();
> #endif /* __ARCH_WANT_INTERRUPTS_ON_CTXSW */
> finish_lock_switch(rq, prev);
> + trace_sched_stat_sleeptime(current, rq->clock);
>
> fire_sched_in_preempt_notifiers(current);
> if (mm)



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