* /proc/$PID/sched does not take PID namespace into account
@ 2013-09-03 14:22 Emmanuel Deloget
2013-09-09 11:01 ` Peter Zijlstra
0 siblings, 1 reply; 5+ messages in thread
From: Emmanuel Deloget @ 2013-09-03 14:22 UTC (permalink / raw)
To: [ML] linux-kernel; +Cc: Emmanuel Deloget, Ingo Molnar, Peter Zijlstra
[-- Attachment #1: Type: text/plain, Size: 2580 bytes --]
Hello,
(please CC me when answering this mail ; and sorry for my borken
English).
I noticed that when a process is executed in a PID namespace it can
still find his real PID by parsing /proc/$PID_IN_NS/sched.
(in this example I created a new PID namespace and ran /bin/bash at
PID 1)
# uname -a
Linux my-thinkpad 3.9-1-amd64 #1 SMP Debian 3.9.6-1 x86_64 GNU/Linux
#
# pidof bash
1
# head -n 1 /proc/1/sched
bash (14957, #threads: 1)
# cat /proc/1/stat
1 (bash) S 0 1 0 34823 220 4202752 11359 (...)
In the root PID namespace
# pidof bash
(...) 14957 (...)
# head -n 1 /proc/14957/sched
bash (14957, #threads: 1)
# cat /proc/14957/stat
14957 (bash) S 14956 14957 23465 34823 14957 4202752 11386 (...)
The principle of least surprise tells me that if my PID is n in a
particular PID namespace then every stat or debug info should tell
me that my PID is n (i.e. I should not be able to get the real PID
of my program). This is a consistency issue: if I get different
information from different sources I may not be able to tell which
one is the right one.
The issue (if this is really an issue) lies in kernel/sched/debug.c,
function proc_sched_show_task(). The code says [1]:
SEQ_printf(m, "%s (%d, #threads: %d)\n", p->comm, p->pid,
get_nr_threads(p));
I understand that you're not supposed to use the content of a /proc
file that has been generated by a kernel source file named "debug.c"
in a production environment yet several distributions out there seems
to enable this by default (at least the Debian distribution I'm using
does it).
I see a few options:
* either it's a bug and it should be corrected (I'm not sure how to
do it; the printed PID should reflect the current PID namespace
and I don't how how to get this information).
* or it has been decided on purpose (i.e. it's not a bug);
/proc/$PID/sched then offers a reliable way to get the real PID
of any process, including processes that run in a child PID
namespace.
* or it's a bug but it cannot be corrected (kernel ABI ; it has been
here for a looooong time - possibly since the PID namespace
integration).
(There might be other options here).
In the two last cases there is no need for a patch but I'd be happy
if someone explains the reasoning.
Best regards,
-- Emmanuel Deloget
[1]: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/kernel/sched/debug.c?id=refs/tags/v3.11#n495
[2]: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/kernel/sched/debug.c?id=refs/tags/v3.11#n118
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email;internet:emmanuel.deloget@efixo.com
title:Team Leader
tel;work:04 88 15 50 77
url:www.sfr.fr
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: /proc/$PID/sched does not take PID namespace into account
2013-09-03 14:22 /proc/$PID/sched does not take PID namespace into account Emmanuel Deloget
@ 2013-09-09 11:01 ` Peter Zijlstra
2013-09-09 13:58 ` Emmanuel Deloget
` (2 more replies)
0 siblings, 3 replies; 5+ messages in thread
From: Peter Zijlstra @ 2013-09-09 11:01 UTC (permalink / raw)
To: Emmanuel Deloget; +Cc: [ML] linux-kernel, Ingo Molnar
On Tue, Sep 03, 2013 at 04:22:33PM +0200, Emmanuel Deloget wrote:
> The issue (if this is really an issue) lies in kernel/sched/debug.c,
> function proc_sched_show_task(). The code says [1]:
>
> SEQ_printf(m, "%s (%d, #threads: %d)\n", p->comm, p->pid,
> get_nr_threads(p));
>
> I see a few options:
>
> * either it's a bug and it should be corrected (I'm not sure how to
> do it; the printed PID should reflect the current PID namespace
> and I don't how how to get this information).
I suppose something like the below ought to work? -- completely
untested, please confirm.
---
Subject: sched, debug: Use PID namespaces
Emmanuel reported that /proc/sched_debug didn't report the right PIDs
when using namespaces, cure this.
Reported-by: Emmanuel Deloget <emmanuel.deloget@efixo.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
---
kernel/sched/debug.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index e076bdd..e30bf44 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -124,7 +124,7 @@ print_task(struct seq_file *m, struct rq *rq, struct task_struct *p)
SEQ_printf(m, " ");
SEQ_printf(m, "%15s %5d %9Ld.%06ld %9Ld %5d ",
- p->comm, p->pid,
+ p->comm, task_pid(p),,
SPLIT_NS(p->se.vruntime),
(long long)(p->nvcsw + p->nivcsw),
p->prio);
@@ -289,7 +289,7 @@ do { \
P(nr_load_updates);
P(nr_uninterruptible);
PN(next_balance);
- P(curr->pid);
+ P(task_pid(curr));
PN(clock);
P(cpu_load[0]);
P(cpu_load[1]);
@@ -492,7 +492,7 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m)
{
unsigned long nr_switches;
- SEQ_printf(m, "%s (%d, #threads: %d)\n", p->comm, p->pid,
+ SEQ_printf(m, "%s (%d, #threads: %d)\n", p->comm, task_pid(p),
get_nr_threads(p));
SEQ_printf(m,
"---------------------------------------------------------"
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: /proc/$PID/sched does not take PID namespace into account
2013-09-09 11:01 ` Peter Zijlstra
@ 2013-09-09 13:58 ` Emmanuel Deloget
2013-09-10 9:18 ` Peter Zijlstra
2013-09-12 18:05 ` [tip:sched/core] sched/debug: Take " tip-bot for Peter Zijlstra
2 siblings, 0 replies; 5+ messages in thread
From: Emmanuel Deloget @ 2013-09-09 13:58 UTC (permalink / raw)
To: Peter Zijlstra; +Cc: [ML] linux-kernel, Ingo Molnar
[-- Attachment #1: Type: text/plain, Size: 2203 bytes --]
Hello,
On 09/09/2013 13:01, Peter Zijlstra wrote:
> On Tue, Sep 03, 2013 at 04:22:33PM +0200, Emmanuel Deloget wrote:
>> The issue (if this is really an issue) lies in kernel/sched/debug.c,
>> function proc_sched_show_task(). The code says [1]:
>>
>> SEQ_printf(m, "%s (%d, #threads: %d)\n", p->comm, p->pid,
>> get_nr_threads(p));
>>
>> I see a few options:
>>
>> * either it's a bug and it should be corrected (I'm not sure how to
>> do it; the printed PID should reflect the current PID namespace
>> and I don't how how to get this information).
> I suppose something like the below ought to work? -- completely
> untested, please confirm.
Thanks !
I'll test that as soon as possible and I'll report to you.
Best regards,
-- Emmanuel Deloget
>
> ---
> Subject: sched, debug: Use PID namespaces
>
> Emmanuel reported that /proc/sched_debug didn't report the right PIDs
> when using namespaces, cure this.
>
> Reported-by: Emmanuel Deloget <emmanuel.deloget@efixo.com>
> Signed-off-by: Peter Zijlstra <peterz@infradead.org>
> ---
> kernel/sched/debug.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
> index e076bdd..e30bf44 100644
> --- a/kernel/sched/debug.c
> +++ b/kernel/sched/debug.c
> @@ -124,7 +124,7 @@ print_task(struct seq_file *m, struct rq *rq, struct task_struct *p)
> SEQ_printf(m, " ");
>
> SEQ_printf(m, "%15s %5d %9Ld.%06ld %9Ld %5d ",
> - p->comm, p->pid,
> + p->comm, task_pid(p),,
> SPLIT_NS(p->se.vruntime),
> (long long)(p->nvcsw + p->nivcsw),
> p->prio);
> @@ -289,7 +289,7 @@ do { \
> P(nr_load_updates);
> P(nr_uninterruptible);
> PN(next_balance);
> - P(curr->pid);
> + P(task_pid(curr));
> PN(clock);
> P(cpu_load[0]);
> P(cpu_load[1]);
> @@ -492,7 +492,7 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m)
> {
> unsigned long nr_switches;
>
> - SEQ_printf(m, "%s (%d, #threads: %d)\n", p->comm, p->pid,
> + SEQ_printf(m, "%s (%d, #threads: %d)\n", p->comm, task_pid(p),
> get_nr_threads(p));
> SEQ_printf(m,
> "---------------------------------------------------------"
> .
>
--
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fn:Emmanuel Deloget
n:Deloget;Emmanuel
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email;internet:emmanuel.deloget@efixo.com
title:Team Leader
tel;work:04 88 15 50 77
url:www.sfr.fr
version:2.1
end:vcard
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: /proc/$PID/sched does not take PID namespace into account
2013-09-09 11:01 ` Peter Zijlstra
2013-09-09 13:58 ` Emmanuel Deloget
@ 2013-09-10 9:18 ` Peter Zijlstra
2013-09-12 18:05 ` [tip:sched/core] sched/debug: Take " tip-bot for Peter Zijlstra
2 siblings, 0 replies; 5+ messages in thread
From: Peter Zijlstra @ 2013-09-10 9:18 UTC (permalink / raw)
To: Emmanuel Deloget; +Cc: [ML] linux-kernel, Ingo Molnar
On Mon, Sep 09, 2013 at 01:01:41PM +0200, Peter Zijlstra wrote:
> On Tue, Sep 03, 2013 at 04:22:33PM +0200, Emmanuel Deloget wrote:
> > The issue (if this is really an issue) lies in kernel/sched/debug.c,
> > function proc_sched_show_task(). The code says [1]:
> >
> > SEQ_printf(m, "%s (%d, #threads: %d)\n", p->comm, p->pid,
> > get_nr_threads(p));
> >
>
> > I see a few options:
> >
> > * either it's a bug and it should be corrected (I'm not sure how to
> > do it; the printed PID should reflect the current PID namespace
> > and I don't how how to get this information).
>
> I suppose something like the below ought to work? -- completely
> untested, please confirm.
>
> ---
> Subject: sched, debug: Use PID namespaces
>
> Emmanuel reported that /proc/sched_debug didn't report the right PIDs
> when using namespaces, cure this.
>
> Reported-by: Emmanuel Deloget <emmanuel.deloget@efixo.com>
> Signed-off-by: Peter Zijlstra <peterz@infradead.org>
> ---
> kernel/sched/debug.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
> index e076bdd..e30bf44 100644
> --- a/kernel/sched/debug.c
> +++ b/kernel/sched/debug.c
> @@ -124,7 +124,7 @@ print_task(struct seq_file *m, struct rq *rq, struct task_struct *p)
> SEQ_printf(m, " ");
>
> SEQ_printf(m, "%15s %5d %9Ld.%06ld %9Ld %5d ",
> - p->comm, p->pid,
> + p->comm, task_pid(p),,
> SPLIT_NS(p->se.vruntime),
> (long long)(p->nvcsw + p->nivcsw),
> p->prio);
> @@ -289,7 +289,7 @@ do { \
> P(nr_load_updates);
> P(nr_uninterruptible);
> PN(next_balance);
> - P(curr->pid);
> + P(task_pid(curr));
> PN(clock);
> P(cpu_load[0]);
> P(cpu_load[1]);
> @@ -492,7 +492,7 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m)
> {
> unsigned long nr_switches;
>
> - SEQ_printf(m, "%s (%d, #threads: %d)\n", p->comm, p->pid,
> + SEQ_printf(m, "%s (%d, #threads: %d)\n", p->comm, task_pid(p),
> get_nr_threads(p));
> SEQ_printf(m,
> "---------------------------------------------------------"
Please do s/task_pid/task_pid_nr/g on this before trying.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [tip:sched/core] sched/debug: Take PID namespace into account
2013-09-09 11:01 ` Peter Zijlstra
2013-09-09 13:58 ` Emmanuel Deloget
2013-09-10 9:18 ` Peter Zijlstra
@ 2013-09-12 18:05 ` tip-bot for Peter Zijlstra
2 siblings, 0 replies; 5+ messages in thread
From: tip-bot for Peter Zijlstra @ 2013-09-12 18:05 UTC (permalink / raw)
To: linux-tip-commits
Cc: linux-kernel, hpa, mingo, peterz, tglx, emmanuel.deloget
Commit-ID: fc840914e9b07ab4685c195e1e54e58de4f84c03
Gitweb: http://git.kernel.org/tip/fc840914e9b07ab4685c195e1e54e58de4f84c03
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Mon, 9 Sep 2013 13:01:41 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 12 Sep 2013 19:14:16 +0200
sched/debug: Take PID namespace into account
Emmanuel reported that /proc/sched_debug didn't report the right PIDs
when using namespaces, cure this.
Reported-by: Emmanuel Deloget <emmanuel.deloget@efixo.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20130909110141.GM31370@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/sched/debug.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index e076bdd..1965599 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -124,7 +124,7 @@ print_task(struct seq_file *m, struct rq *rq, struct task_struct *p)
SEQ_printf(m, " ");
SEQ_printf(m, "%15s %5d %9Ld.%06ld %9Ld %5d ",
- p->comm, p->pid,
+ p->comm, task_pid_nr(p),
SPLIT_NS(p->se.vruntime),
(long long)(p->nvcsw + p->nivcsw),
p->prio);
@@ -289,7 +289,7 @@ do { \
P(nr_load_updates);
P(nr_uninterruptible);
PN(next_balance);
- P(curr->pid);
+ SEQ_printf(m, " .%-30s: %ld\n", "curr->pid", (long)(task_pid_nr(rq->curr)));
PN(clock);
P(cpu_load[0]);
P(cpu_load[1]);
@@ -492,7 +492,7 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m)
{
unsigned long nr_switches;
- SEQ_printf(m, "%s (%d, #threads: %d)\n", p->comm, p->pid,
+ SEQ_printf(m, "%s (%d, #threads: %d)\n", p->comm, task_pid_nr(p),
get_nr_threads(p));
SEQ_printf(m,
"---------------------------------------------------------"
^ permalink raw reply related [flat|nested] 5+ messages in thread
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Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
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2013-09-03 14:22 /proc/$PID/sched does not take PID namespace into account Emmanuel Deloget
2013-09-09 11:01 ` Peter Zijlstra
2013-09-09 13:58 ` Emmanuel Deloget
2013-09-10 9:18 ` Peter Zijlstra
2013-09-12 18:05 ` [tip:sched/core] sched/debug: Take " tip-bot for Peter Zijlstra
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