linux-kernel - Re: process time

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 01 Sep 2011 12:11:24 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	David Miller <davem@...emloft.net>, linux-kernel@...r.kernel.org
Subject: Re: process time < thread time?

On Thu, 2011-09-01 at 11:56 +0200, Thomas Gleixner wrote:
> The untested patch below should cure this.
> 

> diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
> index 58f405b..42378cb 100644
> --- a/kernel/posix-cpu-timers.c
> +++ b/kernel/posix-cpu-timers.c
> @@ -250,7 +250,7 @@ void thread_group_cputime(struct task_struct *tsk,
> struct task_cputime *times)
>         do {
>                 times->utime = cputime_add(times->utime, t->utime);
>                 times->stime = cputime_add(times->stime, t->stime);
> -               times->sum_exec_runtime += t->se.sum_exec_runtime;
> +               times->sum_exec_runtime += task_sched_runtime(t);
>         } while_each_thread(tsk, t);
>  out:
>         rcu_read_unlock(); 

I think we just deadlocked:

cpu_clock_sample_group()
  CPUCLOCK_SCHED: thread_group_sched_runtime()
    task_rq_lock()        <-.
    thread_group_cputime()  |
      task_sched_runtime()  |
       task_rq_lock() ------'


Also, having to take locks here is sad, but yeah if we want to cure this
there's not much we can do about that.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/