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Message-ID: <6599ad830701150122g7156a599t1b3dd3af9f5f821b@mail.gmail.com>
Date: Mon, 15 Jan 2007 01:22:16 -0800
From: "Paul Menage" <menage@...gle.com>
To: balbir@...ibm.com
Cc: akpm@...l.org, pj@....com, sekharan@...ibm.com, dev@...ru,
xemul@...ru, serue@...ibm.com, vatsa@...ibm.com,
ckrm-tech@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
rohitseth@...gle.com, mbligh@...gle.com, winget@...gle.com,
containers@...ts.osdl.org, devel@...nvz.org
Subject: Re: [PATCH 1/1] Fix a panic while mouting containers on powerpc and some other small cleanups (Re: [ckrm-tech] [PATCH 4/6] containers: Simple CPU accounting container subsystem)
On 1/15/07, Balbir Singh <balbir@...ibm.com> wrote:
>
> In sched.c, account_user_time() can be called with the task p set to rq->idle.
> Since idle tasks do not belong to any container, this was causing a panic in
> task_ca() in cpu_acct.c.
How come that didn't cause a problem on x86_64? If this is an
inconsistency between architectures then perhaps it ought to be
cleaned up.
Additionally, I think that we should make the idle tasks members of
the root container(s), to remove this special case. (I'm a bit
surprised that they're not already - I thought that the early
container initialization was early enough that the idle tasks hadn't
yet been forked. Is that different on PowerPC?
>
> Multiplying the time by 1000 is not correct in cpuusage_read(). The code
> has been converted to use the correct cputime API.
Thanks.
>
> Add mount/umount callbacks.
I'm not sure I like the mount/unmount callbacks. What exactly are you
trying to gain from them? My intention was that the
cont->subsys[i]->container = cont;
line in container_get_sb() was doing essentially this - i.e. the
container_subsys_state for the root container in a subsystem is
already kept up to date by the container system, and the subsystem can
rely on the "container" field in the container_subsys_state.
Thanks,
Paul
>
> Signed-off-by: Balbir Singh <balbir@...ibm.com>
> ---
>
> kernel/cpu_acct.c | 29 +++++++++++++++++++++++------
> kernel/sched.c | 17 +++++++++++------
> 2 files changed, 34 insertions(+), 12 deletions(-)
>
> diff -puN kernel/cpu_acct.c~fix-cpuacct-panic-on-mount kernel/cpu_acct.c
> --- linux-2.6.20-rc3/kernel/cpu_acct.c~fix-cpuacct-panic-on-mount 2007-01-15
> 14:23:20.000000000 +0530
> +++ linux-2.6.20-rc3-balbir/kernel/cpu_acct.c 2007-01-15 14:23:20.000000000 +0530
> @@ -22,6 +22,7 @@ struct cpuacct {
> };
>
> static struct container_subsys cpuacct_subsys;
> +static struct container *root;
>
> static inline struct cpuacct *container_ca(struct container *cont)
> {
> @@ -49,6 +50,16 @@ static void cpuacct_destroy(struct conta
> kfree(container_ca(cont));
> }
>
> +static void cpuacct_mount(struct container_subsys *ss, struct container *cont)
> +{
> + root = cont;
> +}
> +
> +static void cpuacct_umount(struct container_subsys *ss, struct container *cont)
> +{
> + root = NULL;
> +}
> +
> static ssize_t cpuusage_read(struct container *cont,
> struct cftype *cft,
> struct file *file,
> @@ -57,6 +68,7 @@ static ssize_t cpuusage_read(struct cont
> {
> struct cpuacct *ca = container_ca(cont);
> cputime64_t time;
> + unsigned long time_in_jiffies;
> char usagebuf[64];
> char *s = usagebuf;
>
> @@ -64,9 +76,8 @@ static ssize_t cpuusage_read(struct cont
> time = ca->time;
> spin_unlock_irq(&ca->lock);
>
> - time *= 1000;
> - do_div(time, HZ);
> - s += sprintf(s, "%llu", (unsigned long long) time);
> + time_in_jiffies = cputime_to_jiffies(time);
> + s += sprintf(s, "%llu\n", (unsigned long long) time_in_jiffies);
>
> return simple_read_from_buffer(buf, nbytes, ppos, usagebuf, s - usagebuf);
> }
> @@ -83,12 +94,13 @@ static int cpuacct_populate(struct conta
> }
>
>
> -void cpuacct_charge(struct task_struct *task, cputime_t cputime) {
> +void cpuacct_charge(struct task_struct *task, cputime_t cputime)
> +{
>
> struct cpuacct *ca;
> unsigned long flags;
>
> - if (cpuacct_subsys.subsys_id < 0) return;
> + if (cpuacct_subsys.subsys_id < 0 || !root) return;
> rcu_read_lock();
> ca = task_ca(task);
> if (ca) {
> @@ -104,13 +116,18 @@ static struct container_subsys cpuacct_s
> .create = cpuacct_create,
> .destroy = cpuacct_destroy,
> .populate = cpuacct_populate,
> + .mount = cpuacct_mount,
> + .umount = cpuacct_umount,
> .subsys_id = -1,
> };
>
>
> int __init init_cpuacct(void)
> {
> - int id = container_register_subsys(&cpuacct_subsys);
> + int id;
> +
> + root = NULL;
> + id = container_register_subsys(&cpuacct_subsys);
> return id < 0 ? id : 0;
> }
>
> diff -puN kernel/sched.c~fix-cpuacct-panic-on-mount kernel/sched.c
> --- linux-2.6.20-rc3/kernel/sched.c~fix-cpuacct-panic-on-mount 2007-01-15
> 14:23:20.000000000 +0530
> +++ linux-2.6.20-rc3-balbir/kernel/sched.c 2007-01-15 14:23:20.000000000 +0530
> @@ -3067,10 +3067,17 @@ void account_user_time(struct task_struc
> {
> struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
> cputime64_t tmp;
> + struct rq *rq = this_rq();
>
> p->utime = cputime_add(p->utime, cputime);
>
> - cpuacct_charge(p, cputime);
> + /*
> + * On powerpc this routine can be called with p set to the idle
> + * task of the cpu. idle tasks don't really belong to any
> + * container.
> + */
> + if (p != rq->idle)
> + cpuacct_charge(p, cputime);
>
> /* Add user time to cpustat. */
> tmp = cputime_to_cputime64(cputime);
> @@ -3095,18 +3102,16 @@ void account_system_time(struct task_str
>
> p->stime = cputime_add(p->stime, cputime);
>
> - if (p != rq->idle)
> - cpuacct_charge(p, cputime);
> -
> /* Add system time to cpustat. */
> tmp = cputime_to_cputime64(cputime);
> if (hardirq_count() - hardirq_offset)
> cpustat->irq = cputime64_add(cpustat->irq, tmp);
> else if (softirq_count())
> cpustat->softirq = cputime64_add(cpustat->softirq, tmp);
> - else if (p != rq->idle)
> + else if (p != rq->idle) {
> cpustat->system = cputime64_add(cpustat->system, tmp);
> - else if (atomic_read(&rq->nr_iowait) > 0)
> + cpuacct_charge(p, cputime);
> + } else if (atomic_read(&rq->nr_iowait) > 0)
> cpustat->iowait = cputime64_add(cpustat->iowait, tmp);
> else
> cpustat->idle = cputime64_add(cpustat->idle, tmp);
> _
>
> Balbir Singh
> Linux Technology Center
> Bangalore, IBM ISTL
>
-
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