On 2/19/15 12:06 AM, Adrian Hunter wrote:
/* not supported, confirm error related to PERF_FLAG_FD_CLOEXEC */
- fd = sys_perf_event_open(&attr, pid, cpu, -1, 0);
+ fd = sys_perf_event_open(&attr, 0, cpu, -1, 0);
I would prefer to avoid pid = 0 unless necessary and so just do the same
thing again i.e.
while (1) {
fd = sys_perf_event_open(&attr, pid, cpu, -1, 0);
if (fd < 0 && pid == -1 && errno == EACCES) {
pid = 0;
continue;
}
break;
}
The probing is getting of hand. In this case the intent is a probe for a
flag and flags are the first thing checked kernel side. Given that the
parameters passed to sys_perf_event_open should be as simple and known
safe as possible. pid = -1 has known limitations. Why can't pid just be
getpid() in both cases?
Simplifies this function a lot and removes the need for sched_getcpu(). So
pid = getpid();
fd = sys_perf_event_open(&attr, pid, -1, -1, PERF_FLAG_FD_CLOEXEC);
and if that fails
fd = sys_perf_event_open(&attr, pid, -1, -1, 0);
Why is anything more complicated needed?
David
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