[PATCH] sched/cpuacct: Check for NULL when using task_pt_regs()

[PATCH] sched/cpuacct: Check for NULL when using task_pt_regs()

[Anton Blanchard]

task_pt_regs() can return NULL for kernel threads, so add a check.
This fixes an oops at boot on ppc64.

Fixes: d740037fac70 ("sched/cpuacct: Split usage accounting into user_usage and sys_usage")
Signed-off-by: Anton Blanchard <anton@samba.org>
Reported-and-Tested-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
---

diff --git a/kernel/sched/cpuacct.c b/kernel/sched/cpuacct.c
index df947e0..41f85c4 100644
--- a/kernel/sched/cpuacct.c
+++ b/kernel/sched/cpuacct.c
@@ -316,12 +316,11 @@ static struct cftype files[] = {
 void cpuacct_charge(struct task_struct *tsk, u64 cputime)
 {
 	struct cpuacct *ca;
-	int index;
+	int index = CPUACCT_USAGE_SYSTEM;
+	struct pt_regs *regs = task_pt_regs(tsk);
 
-	if (user_mode(task_pt_regs(tsk)))
+	if (regs && user_mode(regs))
 		index = CPUACCT_USAGE_USER;
-	else
-		index = CPUACCT_USAGE_SYSTEM;
 
 	rcu_read_lock();
 

Re: [PATCH] sched/cpuacct: Check for NULL when using task_pt_regs()

[Ingo Molnar]

* Michael Ellerman <mpe@ellerman.id.au> wrote:

> On Wed, 2016-04-13 at 09:43 +0200, Ingo Molnar wrote:
> > * Srikar Dronamraju <srikar@linux.vnet.ibm.com> wrote:
> > 
> > > * Anton Blanchard <anton@samba.org> [2016-04-06 21:59:50]:
> > > 
> > > > Looks good, and the patch below does fix the oops for me.
> > > > 
> > > > Anton
> > > > --
> > > > 
> > > > task_pt_regs() can return NULL for kernel threads, so add a check.
> > > > This fixes an oops at boot on ppc64.
> > > > 
> > > > Signed-off-by: Anton Blanchard <anton@samba.org>
> > > 
> > > Works for me too.
> > > 
> > > Reported-and-Tested-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
> > 
> > Could someone please re-send the fix, because it has not reached me nor lkml.
> 
> It did hit LKML:
> 
> http://lkml.kernel.org/r/20160406215950.04bc3f0b@kryten
> 
> But that did have some verbiage at the top.
> 
> Anton's also resent it directly To you.

So it was in my Spam folder, due to the following SPF softfail:

  Received-SPF: softfail (google.com: domain of transitioning anton@samba.org does not designate 198.145.29.136 as permitted sender) client-ip=198.145.29.136;

have the patch now.

Thanks,

	Ingo

Re: [PATCH] sched/cpuacct: Check for NULL when using task_pt_regs()

[Michael Ellerman]

On Wed, 2016-04-13 at 09:43 +0200, Ingo Molnar wrote:
> * Srikar Dronamraju <srikar@linux.vnet.ibm.com> wrote:
> 
> > * Anton Blanchard <anton@samba.org> [2016-04-06 21:59:50]:
> > 
> > > Looks good, and the patch below does fix the oops for me.
> > > 
> > > Anton
> > > --
> > > 
> > > task_pt_regs() can return NULL for kernel threads, so add a check.
> > > This fixes an oops at boot on ppc64.
> > > 
> > > Signed-off-by: Anton Blanchard <anton@samba.org>
> > 
> > Works for me too.
> > 
> > Reported-and-Tested-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
> 
> Could someone please re-send the fix, because it has not reached me nor lkml.

It did hit LKML:

http://lkml.kernel.org/r/20160406215950.04bc3f0b@kryten

But that did have some verbiage at the top.

Anton's also resent it directly To you.

cheers

Re: [PATCH] sched/cpuacct: Check for NULL when using task_pt_regs()

[Ingo Molnar]

* Srikar Dronamraju <srikar@linux.vnet.ibm.com> wrote:

> * Anton Blanchard <anton@samba.org> [2016-04-06 21:59:50]:
> 
> > Looks good, and the patch below does fix the oops for me.
> > 
> > Anton
> > --
> > 
> > task_pt_regs() can return NULL for kernel threads, so add a check.
> > This fixes an oops at boot on ppc64.
> > 
> > Signed-off-by: Anton Blanchard <anton@samba.org>
> 
> Works for me too.
> 
> Reported-and-Tested-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

Could someone please re-send the fix, because it has not reached me nor lkml.

Thanks,

	Ingo

RE: [PATCH] sched/cpuacct: Check for NULL when using task_pt_regs()

[Zhao Lei]

> -----Original Message-----
> From: Srikar Dronamraju [mailto:srikar@linux.vnet.ibm.com]
> Sent: Wednesday, April 06, 2016 9:27 PM
> To: Anton Blanchard <anton@samba.org>
> Cc: Peter Zijlstra <peterz@infradead.org>; Ingo Molnar <mingo@kernel.org>;
> tglx@linutronix.de; efault@gmx.de; htejun@gmail.com;
> linux-kernel@vger.kernel.org; tj@kernel.org; torvalds@linux-foundation.org;
> zhaolei@cn.fujitsu.com; yangds.fnst@cn.fujitsu.com; hpa@zytor.com; Stephen
> Rothwell <sfr@canb.auug.org.au>; Michael Ellerman <mpe@ellerman.id.au>;
> linuxppc-dev@lists.ozlabs.org
> Subject: Re: [PATCH] sched/cpuacct: Check for NULL when using task_pt_regs()
> 
> * Anton Blanchard <anton@samba.org> [2016-04-06 21:59:50]:
> 
> > Looks good, and the patch below does fix the oops for me.
> >
> > Anton
> > --
> >
> > task_pt_regs() can return NULL for kernel threads, so add a check.
> > This fixes an oops at boot on ppc64.
> >
> > Signed-off-by: Anton Blanchard <anton@samba.org>
> 
> Works for me too.
> 
> Reported-and-Tested-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
> 
Thanks, all

I tested it in the vm(can not boot before fix):

[single cpu]
# for f in cpuacct.*; do echo "$f: "; cat $f; done
cpuacct.stat:
user 260
system 451
cpuacct.usage:
6923456654
cpuacct.usage_percpu:
6963446178
cpuacct.usage_percpu_sys:
2610934362
cpuacct.usage_percpu_user:
4451667140
cpuacct.usage_sys:
2612684054
cpuacct.usage_user:
4540275322
#

[2 cpu wih 8 maxcpus]
# for f in cpuacct.*; do echo "$f: "; cat $f; done
cpuacct.stat:
user 205
system 536
cpuacct.usage:
7293688020
cpuacct.usage_percpu:
3785674990 3551323200 0 0 0 0 0 0
cpuacct.usage_percpu_sys:
2227281124 1635060584 0 0 0 0 0 0
cpuacct.usage_percpu_user:
1567487176 1992278818 0 0 0 0 0 0
cpuacct.usage_sys:
3863445982
cpuacct.usage_user:
3643874038
#

# cat /proc/cpuinfo
processor       : 0
cpu             : POWER7 (raw), altivec supported
clock           : 1000.000000MHz
revision        : 2.3 (pvr 003f 0203)

processor       : 1
cpu             : POWER7 (raw), altivec supported
clock           : 1000.000000MHz
revision        : 2.3 (pvr 003f 0203)

timebase        : 512000000
platform        : pSeries
model           : IBM pSeries (emulated by qemu)
machine         : CHRP IBM pSeries (emulated by qemu)
#

Thanks
Zhaolei

> --
> Thanks and Regards
> Srikar Dronamraju
> 

Re: [PATCH] sched/cpuacct: Check for NULL when using task_pt_regs()

[Srikar Dronamraju]

* Anton Blanchard <anton@samba.org> [2016-04-06 21:59:50]:

> Looks good, and the patch below does fix the oops for me.
> 
> Anton
> --
> 
> task_pt_regs() can return NULL for kernel threads, so add a check.
> This fixes an oops at boot on ppc64.
> 
> Signed-off-by: Anton Blanchard <anton@samba.org>

Works for me too.

Reported-and-Tested-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

-- 
Thanks and Regards
Srikar Dronamraju

[PATCH] sched/cpuacct: Check for NULL when using task_pt_regs()

[Anton Blanchard]

Hi Peter,

> Ah, so sometihng like:
> 
> 	struct pt_regs *regs = task_pt_regs();
> 	int index = CPUACCT_USAGE_SYSTEM;
> 
> 	if (regs && user_mode(regs))
> 		index = CPUACCT_USAGE_USER;
> 
> should work, right?

Looks good, and the patch below does fix the oops for me.

Anton
--

task_pt_regs() can return NULL for kernel threads, so add a check.
This fixes an oops at boot on ppc64.

Signed-off-by: Anton Blanchard <anton@samba.org>
---

diff --git a/kernel/sched/cpuacct.c b/kernel/sched/cpuacct.c
index df947e0..41f85c4 100644
--- a/kernel/sched/cpuacct.c
+++ b/kernel/sched/cpuacct.c
@@ -316,12 +316,11 @@ static struct cftype files[] = {
 void cpuacct_charge(struct task_struct *tsk, u64 cputime)
 {
 	struct cpuacct *ca;
-	int index;
+	int index = CPUACCT_USAGE_SYSTEM;
+	struct pt_regs *regs = task_pt_regs(tsk);
 
-	if (user_mode(task_pt_regs(tsk)))
+	if (regs && user_mode(regs))
 		index = CPUACCT_USAGE_USER;
-	else
-		index = CPUACCT_USAGE_SYSTEM;
 
 	rcu_read_lock();