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Date: Mon, 15 Jan 2007 14:34:53 +0530
From: Balbir Singh <balbir@...ibm.com>
To: balbir@...ibm.com
CC: Paul Menage <menage@...gle.com>, 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: [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)
Balbir Singh wrote:
> Paul Menage wrote:
>> On 1/10/07, Balbir Singh <balbir@...ibm.com> wrote:
>>> I have run into a problem running this patch on a powerpc box. Basically,
>>> the machine panics as soon as I mount the container filesystem with
>> This is a multi-processor system?
>>
> Hi, Paul,
>
> I figured out the reason for the panic. Here are the fixes
>
Here is the second patch and the real fix in sched.c
Fix coding style in cpuacct_charge()
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.
Multiplying the time by 1000 is not correct in cpuusage_read(). The code
has been converted to use the correct cputime API.
Add mount/umount callbacks.
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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