Messages in this thread | | | Subject | Re: [PATCH] Read THREAD_CPUTIME clock from other processes. | From | Dario Faggioli <> | Date | Thu, 23 Dec 2010 18:38:21 +0100 |
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On Thu, 2010-12-23 at 17:44 +0100, Oleg Nesterov wrote: > > Therefore, this patch removes such limitation and enables the > > following behaviour, for the threaded and process-based case, > > respectively: > > Can't comment, I never understood this. > If I can ask... What's that you never understood? Why the limitation is there? Or something else?
> > rcu_read_lock(); > > p = find_task_by_vpid(pid); > > - if (!p || !(CPUCLOCK_PERTHREAD(which_clock) ? > > - same_thread_group(p, current) : has_group_leader_pid(p))) { > > + if (!p) > > error = -EINVAL; > > - } > > This changes the behaviour of sys_clock_settime(). Probably doesn't > matter since it does nothing, but perhaps !CPUCLOCK_PERTHREAD && > !group_leader should result in -EINAVL as before. > Oops, sure, you're right, I can fix this. :-)
> > @@ -349,18 +347,21 @@ int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp) > > rcu_read_lock(); > > p = find_task_by_vpid(pid); > > if (p) { > > - if (CPUCLOCK_PERTHREAD(which_clock)) { > > - if (same_thread_group(p, current)) { > > - error = cpu_clock_sample(which_clock, > > - p, &rtn); > > - } > > + > > + if (CPUCLOCK_PERTHREAD(which_clock) && > > + same_thread_group(p, current)) { > > + error = cpu_clock_sample(which_clock, > > + p, &rtn); > > } else { > > read_lock(&tasklist_lock); > > - if (thread_group_leader(p) && p->sighand) { > > + if (!CPUCLOCK_PERTHREAD(which_clock) && > > + thread_group_leader(p) && p->sighand) > > error = > > cpu_clock_sample_group(which_clock, > > - p, &rtn); > > - } > > + p, &rtn); > > + else > > + error = cpu_clock_sample(which_clock, > > + p, &rtn); > > read_unlock(&tasklist_lock); > > Can't understand... why did you duplicate cpu_clock_sample() ? > > IOW, it seems to me you could simply kill the > "if (same_thread_group(p, current)) {" line with the same efect, no? > Well, yes, but looking at the original code I thought that in the ! same_thread_group() case I might need the tasklist_lock...
Am I wrong? Is it there just because of cpu_clock_sample_group()?
Thanks and Regards, Dario
-- <<This happens because I choose it to happen!>> (Raistlin Majere) ---------------------------------------------------------------------- Dario Faggioli, ReTiS Lab, Scuola Superiore Sant'Anna, Pisa (Italy)
http://retis.sssup.it/people/faggioli -- dario.faggioli@jabber.org [unhandled content-type:application/pgp-signature] | |