2.6.30-rc2 hangs in get_measured_perf on tigerton

2.6.30-rc2 hangs in get_measured_perf on tigerton

[Zhang, Yanmin]

My machine hanged with kernel 2.6.30-rc2 when script read
/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor.

opps happens in get_measured_perf:

        cur.aperf.whole = readin.aperf.whole -
                                per_cpu(drv_data, cpu)->saved_aperf;

Because per_cpu(drv_data, cpu)=NULL.

So function get_measured_perf should check if (per_cpu(drv_data, cpu)==NULL)
and return 0 if it's NULL.

Other functions have such checking.

yanmin



--------------sys log------------------

BUG: unable to handle kernel NULL pointer dereference at 0000000000000020
IP: [<ffffffff8021af75>] get_measured_perf+0x4a/0xf9
PGD a7dd88067 PUD a7ccf5067 PMD 0 
Oops: 0000 [#1] SMP 
last sysfs file: /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
CPU 0 
Modules linked in: video output
Pid: 2091, comm: kondemand/0 Not tainted 2.6.30-rc2 #1 MP Server
RIP: 0010:[<ffffffff8021af75>]  [<ffffffff8021af75>] get_measured_perf+0x4a/0xf9
RSP: 0018:ffff880a7d56de20  EFLAGS: 00010246
RAX: 0000000000000000 RBX: 00000046241a42b6 RCX: ffff88004d219000
RDX: 000000000000b660 RSI: 0000000000000020 RDI: 0000000000000001
RBP: ffff880a7f052000 R08: 00000046241a42b6 R09: ffffffff807639f0
R10: 00000000ffffffea R11: ffffffff802207f4 R12: ffff880a7f052000
R13: ffff88004d20e460 R14: 0000000000ddd5a6 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff88004d200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0018 ES: 0018 CR0: 000000008005003b
CR2: 0000000000000020 CR3: 0000000a7f1bf000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process kondemand/0 (pid: 2091, threadinfo ffff880a7d56c000, task ffff880a7d4d18c0)
Stack:
 ffff880a7f052078 ffffffff803efd54 00000046241a42b6 000000462ffa9e95
 0000000000000001 0000000000000001 00000000ffffffea ffffffff8064f41a
 0000000000000012 0000000000000012 ffff880a7f052000 ffffffff80650547
Call Trace:
 [<ffffffff803efd54>] ? kobject_get+0x12/0x17
 [<ffffffff8064f41a>] ? __cpufreq_driver_getavg+0x42/0x57
 [<ffffffff80650547>] ? do_dbs_timer+0x147/0x272
 [<ffffffff80650400>] ? do_dbs_timer+0x0/0x272
 [<ffffffff802474ca>] ? worker_thread+0x15b/0x1f5
 [<ffffffff8024a02c>] ? autoremove_wake_function+0x0/0x2e
 [<ffffffff8024736f>] ? worker_thread+0x0/0x1f5
 [<ffffffff80249f0d>] ? kthread+0x54/0x83
 [<ffffffff8020c87a>] ? child_rip+0xa/0x20
 [<ffffffff80249eb9>] ? kthread+0x0/0x83
 [<ffffffff8020c870>] ? child_rip+0x0/0x20
Code: 99 a6 03 00 31 c9 85 c0 0f 85 c3 00 00 00 89 df 4c 8b 44 24 10 48 c7 c2 60 b6 00 00 48 8b 0c fd e0 30 a5 80 4c 89 c3 48 8b 04 0a <48> 2b 58 20 48 8b 44 24 18 48 89 1c 24 48 8b 34 0a 48 2b 46 28 
RIP  [<ffffffff8021af75>] get_measured_perf+0x4a/0xf9
 RSP <ffff880a7d56de20>
CR2: 0000000000000020
---[ end trace 2b8fac9a49e19ad4 ]---

Re: 2.6.30-rc2 hangs in get_measured_perf on tigerton

[Zhang, Yanmin]

On Wed, 2009-04-15 at 14:01 +0800, Zhang, Yanmin wrote:
> My machine hanged with kernel 2.6.30-rc2 when script read
> /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor.
> 
> opps happens in get_measured_perf:
> 
>         cur.aperf.whole = readin.aperf.whole -
>                                 per_cpu(drv_data, cpu)->saved_aperf;
> 
> Because per_cpu(drv_data, cpu)=NULL.
> 
> So function get_measured_perf should check if (per_cpu(drv_data, cpu)==NULL)
> and return 0 if it's NULL.
> 
> Other functions have such checking.
How about below patch? I tested it on my tigerton machine.

---

--- linux-2.6.30-rc2/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c	2009-04-15 02:24:38.000000000 -0400
+++ linux-2.6.30-rc2_cpufreqbug/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c	2009-04-15 02:31:37.000000000 -0400
@@ -277,6 +277,9 @@ static unsigned int get_measured_perf(st
 	unsigned int perf_percent;
 	unsigned int retval;
 
+	if (unlikely(per_cpu(drv_data, cpu) == NULL))
+		return 0;
+
 	if (smp_call_function_single(cpu, read_measured_perf_ctrs, &readin, 1))
 		return 0;
 

> 
> yanmin
> 
> 
> 
> --------------sys log------------------
> 
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000020
> IP: [<ffffffff8021af75>] get_measured_perf+0x4a/0xf9
> PGD a7dd88067 PUD a7ccf5067 PMD 0 
> Oops: 0000 [#1] SMP 
> last sysfs file: /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
> CPU 0 
> Modules linked in: video output
> Pid: 2091, comm: kondemand/0 Not tainted 2.6.30-rc2 #1 MP Server
> RIP: 0010:[<ffffffff8021af75>]  [<ffffffff8021af75>] get_measured_perf+0x4a/0xf9
> RSP: 0018:ffff880a7d56de20  EFLAGS: 00010246
> RAX: 0000000000000000 RBX: 00000046241a42b6 RCX: ffff88004d219000
> RDX: 000000000000b660 RSI: 0000000000000020 RDI: 0000000000000001
> RBP: ffff880a7f052000 R08: 00000046241a42b6 R09: ffffffff807639f0
> R10: 00000000ffffffea R11: ffffffff802207f4 R12: ffff880a7f052000
> R13: ffff88004d20e460 R14: 0000000000ddd5a6 R15: 0000000000000001
> FS:  0000000000000000(0000) GS:ffff88004d200000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0018 ES: 0018 CR0: 000000008005003b
> CR2: 0000000000000020 CR3: 0000000a7f1bf000 CR4: 00000000000006e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> Process kondemand/0 (pid: 2091, threadinfo ffff880a7d56c000, task ffff880a7d4d18c0)
> Stack:
>  ffff880a7f052078 ffffffff803efd54 00000046241a42b6 000000462ffa9e95
>  0000000000000001 0000000000000001 00000000ffffffea ffffffff8064f41a
>  0000000000000012 0000000000000012 ffff880a7f052000 ffffffff80650547
> Call Trace:
>  [<ffffffff803efd54>] ? kobject_get+0x12/0x17
>  [<ffffffff8064f41a>] ? __cpufreq_driver_getavg+0x42/0x57
>  [<ffffffff80650547>] ? do_dbs_timer+0x147/0x272
>  [<ffffffff80650400>] ? do_dbs_timer+0x0/0x272
>  [<ffffffff802474ca>] ? worker_thread+0x15b/0x1f5
>  [<ffffffff8024a02c>] ? autoremove_wake_function+0x0/0x2e
>  [<ffffffff8024736f>] ? worker_thread+0x0/0x1f5
>  [<ffffffff80249f0d>] ? kthread+0x54/0x83
>  [<ffffffff8020c87a>] ? child_rip+0xa/0x20
>  [<ffffffff80249eb9>] ? kthread+0x0/0x83
>  [<ffffffff8020c870>] ? child_rip+0x0/0x20
> Code: 99 a6 03 00 31 c9 85 c0 0f 85 c3 00 00 00 89 df 4c 8b 44 24 10 48 c7 c2 60 b6 00 00 48 8b 0c fd e0 30 a5 80 4c 89 c3 48 8b 04 0a <48> 2b 58 20 48 8b 44 24 18 48 89 1c 24 48 8b 34 0a 48 2b 46 28 
> RIP  [<ffffffff8021af75>] get_measured_perf+0x4a/0xf9
>  RSP <ffff880a7d56de20>
> CR2: 0000000000000020
> ---[ end trace 2b8fac9a49e19ad4 ]---
> 
> 
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Re: 2.6.30-rc2 hangs in get_measured_perf on tigerton

[Rusty Russell]

On Wed, 15 Apr 2009 03:31:23 pm Zhang, Yanmin wrote:
> My machine hanged with kernel 2.6.30-rc2 when script read
> /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor.
> 
> opps happens in get_measured_perf:
> 
>         cur.aperf.whole = readin.aperf.whole -
>                                 per_cpu(drv_data, cpu)->saved_aperf;
> 
> Because per_cpu(drv_data, cpu)=NULL.
> 
> So function get_measured_perf should check if (per_cpu(drv_data, cpu)==NULL)
> and return 0 if it's NULL.
> 
> Other functions have such checking.

Possibly true, but I can't see that get_measured_perf() ever did.

Unless there's something subtle with preemption no longer being disabled
inside that function...

Cc'd the experts.

Thanks,
Rusty.

> 
> yanmin
> 
> 
> 
> --------------sys log------------------
> 
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000020
> IP: [<ffffffff8021af75>] get_measured_perf+0x4a/0xf9
> PGD a7dd88067 PUD a7ccf5067 PMD 0 
> Oops: 0000 [#1] SMP 
> last sysfs file: /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
> CPU 0 
> Modules linked in: video output
> Pid: 2091, comm: kondemand/0 Not tainted 2.6.30-rc2 #1 MP Server
> RIP: 0010:[<ffffffff8021af75>]  [<ffffffff8021af75>] get_measured_perf+0x4a/0xf9
> RSP: 0018:ffff880a7d56de20  EFLAGS: 00010246
> RAX: 0000000000000000 RBX: 00000046241a42b6 RCX: ffff88004d219000
> RDX: 000000000000b660 RSI: 0000000000000020 RDI: 0000000000000001
> RBP: ffff880a7f052000 R08: 00000046241a42b6 R09: ffffffff807639f0
> R10: 00000000ffffffea R11: ffffffff802207f4 R12: ffff880a7f052000
> R13: ffff88004d20e460 R14: 0000000000ddd5a6 R15: 0000000000000001
> FS:  0000000000000000(0000) GS:ffff88004d200000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0018 ES: 0018 CR0: 000000008005003b
> CR2: 0000000000000020 CR3: 0000000a7f1bf000 CR4: 00000000000006e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> Process kondemand/0 (pid: 2091, threadinfo ffff880a7d56c000, task ffff880a7d4d18c0)
> Stack:
>  ffff880a7f052078 ffffffff803efd54 00000046241a42b6 000000462ffa9e95
>  0000000000000001 0000000000000001 00000000ffffffea ffffffff8064f41a
>  0000000000000012 0000000000000012 ffff880a7f052000 ffffffff80650547
> Call Trace:
>  [<ffffffff803efd54>] ? kobject_get+0x12/0x17
>  [<ffffffff8064f41a>] ? __cpufreq_driver_getavg+0x42/0x57
>  [<ffffffff80650547>] ? do_dbs_timer+0x147/0x272
>  [<ffffffff80650400>] ? do_dbs_timer+0x0/0x272
>  [<ffffffff802474ca>] ? worker_thread+0x15b/0x1f5
>  [<ffffffff8024a02c>] ? autoremove_wake_function+0x0/0x2e
>  [<ffffffff8024736f>] ? worker_thread+0x0/0x1f5
>  [<ffffffff80249f0d>] ? kthread+0x54/0x83
>  [<ffffffff8020c87a>] ? child_rip+0xa/0x20
>  [<ffffffff80249eb9>] ? kthread+0x0/0x83
>  [<ffffffff8020c870>] ? child_rip+0x0/0x20
> Code: 99 a6 03 00 31 c9 85 c0 0f 85 c3 00 00 00 89 df 4c 8b 44 24 10 48 c7 c2 60 b6 00 00 48 8b 0c fd e0 30 a5 80 4c 89 c3 48 8b 04 0a <48> 2b 58 20 48 8b 44 24 18 48 89 1c 24 48 8b 34 0a 48 2b 46 28 
> RIP  [<ffffffff8021af75>] get_measured_perf+0x4a/0xf9
>  RSP <ffff880a7d56de20>
> CR2: 0000000000000020
> ---[ end trace 2b8fac9a49e19ad4 ]---
> 
> 

RE: 2.6.30-rc2 hangs in get_measured_perf on tigerton

[Pallipadi, Venkatesh]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset="utf-8", Size: 4210 bytes --]

 

>-----Original Message-----
>From: cpufreq-owner@vger.kernel.org 
>[mailto:cpufreq-owner@vger.kernel.org] On Behalf Of Rusty Russell
>Sent: Wednesday, April 15, 2009 4:14 AM
>To: Zhang, Yanmin
>Cc: LKML; Pallipadi, Venkatesh; Denis Sadykov; 
>cpufreq@vger.kernel.org; linux-acpi@vger.kernel.org
>Subject: Re: 2.6.30-rc2 hangs in get_measured_perf on tigerton
>
>On Wed, 15 Apr 2009 03:31:23 pm Zhang, Yanmin wrote:
>> My machine hanged with kernel 2.6.30-rc2 when script read
>> /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor.
>> 
>> opps happens in get_measured_perf:
>> 
>>         cur.aperf.whole = readin.aperf.whole -
>>                                 per_cpu(drv_data, cpu)->saved_aperf;
>> 
>> Because per_cpu(drv_data, cpu)=NULL.
>> 
>> So function get_measured_perf should check if 
>(per_cpu(drv_data, cpu)==NULL)
>> and return 0 if it's NULL.
>> 
>> Other functions have such checking.
>
>Possibly true, but I can't see that get_measured_perf() ever did.
>
>Unless there's something subtle with preemption no longer 
>being disabled
>inside that function...
>

Checking the NULL and returning is not an option. We need to
look at average current freq on all CPUs to make correct
next freq decision. Also, per_cpu drv_data should be set
for all CPUs. I will poke a bit at this and get back...

Thanks,
Venki


>> 
>> 
>> --------------sys log------------------
>> 
>> BUG: unable to handle kernel NULL pointer dereference at 
>0000000000000020
>> IP: [<ffffffff8021af75>] get_measured_perf+0x4a/0xf9
>> PGD a7dd88067 PUD a7ccf5067 PMD 0 
>> Oops: 0000 [#1] SMP 
>> last sysfs file: 
>/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
>> CPU 0 
>> Modules linked in: video output
>> Pid: 2091, comm: kondemand/0 Not tainted 2.6.30-rc2 #1 MP Server
>> RIP: 0010:[<ffffffff8021af75>]  [<ffffffff8021af75>] 
>get_measured_perf+0x4a/0xf9
>> RSP: 0018:ffff880a7d56de20  EFLAGS: 00010246
>> RAX: 0000000000000000 RBX: 00000046241a42b6 RCX: ffff88004d219000
>> RDX: 000000000000b660 RSI: 0000000000000020 RDI: 0000000000000001
>> RBP: ffff880a7f052000 R08: 00000046241a42b6 R09: ffffffff807639f0
>> R10: 00000000ffffffea R11: ffffffff802207f4 R12: ffff880a7f052000
>> R13: ffff88004d20e460 R14: 0000000000ddd5a6 R15: 0000000000000001
>> FS:  0000000000000000(0000) GS:ffff88004d200000(0000) 
>knlGS:0000000000000000
>> CS:  0010 DS: 0018 ES: 0018 CR0: 000000008005003b
>> CR2: 0000000000000020 CR3: 0000000a7f1bf000 CR4: 00000000000006e0
>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
>> Process kondemand/0 (pid: 2091, threadinfo ffff880a7d56c000, 
>task ffff880a7d4d18c0)
>> Stack:
>>  ffff880a7f052078 ffffffff803efd54 00000046241a42b6 000000462ffa9e95
>>  0000000000000001 0000000000000001 00000000ffffffea ffffffff8064f41a
>>  0000000000000012 0000000000000012 ffff880a7f052000 ffffffff80650547
>> Call Trace:
>>  [<ffffffff803efd54>] ? kobject_get+0x12/0x17
>>  [<ffffffff8064f41a>] ? __cpufreq_driver_getavg+0x42/0x57
>>  [<ffffffff80650547>] ? do_dbs_timer+0x147/0x272
>>  [<ffffffff80650400>] ? do_dbs_timer+0x0/0x272
>>  [<ffffffff802474ca>] ? worker_thread+0x15b/0x1f5
>>  [<ffffffff8024a02c>] ? autoremove_wake_function+0x0/0x2e
>>  [<ffffffff8024736f>] ? worker_thread+0x0/0x1f5
>>  [<ffffffff80249f0d>] ? kthread+0x54/0x83
>>  [<ffffffff8020c87a>] ? child_rip+0xa/0x20
>>  [<ffffffff80249eb9>] ? kthread+0x0/0x83
>>  [<ffffffff8020c870>] ? child_rip+0x0/0x20
>> Code: 99 a6 03 00 31 c9 85 c0 0f 85 c3 00 00 00 89 df 4c 8b 
>44 24 10 48 c7 c2 60 b6 00 00 48 8b 0c fd e0 30 a5 80 4c 89 c3 
>48 8b 04 0a <48> 2b 58 20 48 8b 44 24 18 48 89 1c 24 48 8b 34 
>0a 48 2b 46 28 
>> RIP  [<ffffffff8021af75>] get_measured_perf+0x4a/0xf9
>>  RSP <ffff880a7d56de20>
>> CR2: 0000000000000020
>> ---[ end trace 2b8fac9a49e19ad4 ]---
>> 
>> 
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[PATCH] x86, acpi_cpufreq: Fix the NULL pointer dereference in get_measured_perf

[Pallipadi, Venkatesh]

Patch below fixes the problem. Yanmin can you please verify.
Len please push this patch along to linus.

Thanks,
Venki


Fix for a regression that was introduced by earlier commit

commit 18b2646fe3babeb40b34a0c1751e0bf5adfdc64c
Author: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Date:   Mon Apr 6 11:26:08 2009 -0700

Regression resulted in the below error happened on systems with
software coordination where per_cpu acpi data will not be initiated for
secondary CPUs in a P-state domain.

On Tue, 2009-04-14 at 23:01 -0700, Zhang, Yanmin wrote:
 My machine hanged with kernel 2.6.30-rc2 when script read
> /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor.
>
> opps happens in get_measured_perf:
>
>         cur.aperf.whole = readin.aperf.whole -
>                                 per_cpu(drv_data, cpu)->saved_aperf;
>
> Because per_cpu(drv_data, cpu)=NULL.
>
> So function get_measured_perf should check if (per_cpu(drv_data,
> cpu)==NULL)
> and return 0 if it's NULL.

--------------sys log------------------

BUG: unable to handle kernel NULL pointer dereference at
0000000000000020
IP: [<ffffffff8021af75>] get_measured_perf+0x4a/0xf9
PGD a7dd88067 PUD a7ccf5067 PMD 0
Oops: 0000 [#1] SMP
last sysfs file: /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
CPU 0
Modules linked in: video output
Pid: 2091, comm: kondemand/0 Not tainted 2.6.30-rc2 #1 MP Server
RIP: 0010:[<ffffffff8021af75>]  [<ffffffff8021af75>]
get_measured_perf+0x4a/0xf9
RSP: 0018:ffff880a7d56de20  EFLAGS: 00010246
RAX: 0000000000000000 RBX: 00000046241a42b6 RCX: ffff88004d219000
RDX: 000000000000b660 RSI: 0000000000000020 RDI: 0000000000000001
RBP: ffff880a7f052000 R08: 00000046241a42b6 R09: ffffffff807639f0
R10: 00000000ffffffea R11: ffffffff802207f4 R12: ffff880a7f052000
R13: ffff88004d20e460 R14: 0000000000ddd5a6 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff88004d200000(0000)
knlGS:0000000000000000
CS:  0010 DS: 0018 ES: 0018 CR0: 000000008005003b
CR2: 0000000000000020 CR3: 0000000a7f1bf000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process kondemand/0 (pid: 2091, threadinfo ffff880a7d56c000, task
ffff880a7d4d18c0)
Stack:
 ffff880a7f052078 ffffffff803efd54 00000046241a42b6 000000462ffa9e95
 0000000000000001 0000000000000001 00000000ffffffea ffffffff8064f41a
 0000000000000012 0000000000000012 ffff880a7f052000 ffffffff80650547
Call Trace:
 [<ffffffff803efd54>] ? kobject_get+0x12/0x17
 [<ffffffff8064f41a>] ? __cpufreq_driver_getavg+0x42/0x57
 [<ffffffff80650547>] ? do_dbs_timer+0x147/0x272
 [<ffffffff80650400>] ? do_dbs_timer+0x0/0x272
 [<ffffffff802474ca>] ? worker_thread+0x15b/0x1f5
 [<ffffffff8024a02c>] ? autoremove_wake_function+0x0/0x2e
 [<ffffffff8024736f>] ? worker_thread+0x0/0x1f5
 [<ffffffff80249f0d>] ? kthread+0x54/0x83
 [<ffffffff8020c87a>] ? child_rip+0xa/0x20
 [<ffffffff80249eb9>] ? kthread+0x0/0x83
 [<ffffffff8020c870>] ? child_rip+0x0/0x20
Code: 99 a6 03 00 31 c9 85 c0 0f 85 c3 00 00 00 89 df 4c 8b 44 24 10 48
c7 c2 60 b6 00 00 48 8b 0c fd e0 30 a5 80 4c 89 c3 48 8b 04 0a <48> 2b
58 20 48 8b 44 24 18 48 89 1c 24 48 8b 34 0a 48 2b 46 28
RIP  [<ffffffff8021af75>] get_measured_perf+0x4a/0xf9
 RSP <ffff880a7d56de20>
CR2: 0000000000000020
---[ end trace 2b8fac9a49e19ad4 ]---

Reported-by: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
---
 arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c |   15 ++++++++++-----
 1 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c b/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
index 837c2c4..d722b8d 100644
--- a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
+++ b/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
@@ -68,11 +68,16 @@ struct acpi_cpufreq_data {
 	unsigned int max_freq;
 	unsigned int resume;
 	unsigned int cpu_feature;
-	u64 saved_aperf, saved_mperf;
 };
 
 static DEFINE_PER_CPU(struct acpi_cpufreq_data *, drv_data);
 
+struct acpi_msr_data {
+	u64 saved_aperf, saved_mperf;
+};
+
+static DEFINE_PER_CPU(struct acpi_msr_data, msr_data);
+
 DEFINE_TRACE(power_mark);
 
 /* acpi_perf_data is a pointer to percpu data. */
@@ -281,11 +286,11 @@ static unsigned int get_measured_perf(struct cpufreq_policy *policy,
 		return 0;
 
 	cur.aperf.whole = readin.aperf.whole -
-				per_cpu(drv_data, cpu)->saved_aperf;
+				per_cpu(msr_data, cpu).saved_aperf;
 	cur.mperf.whole = readin.mperf.whole -
-				per_cpu(drv_data, cpu)->saved_mperf;
-	per_cpu(drv_data, cpu)->saved_aperf = readin.aperf.whole;
-	per_cpu(drv_data, cpu)->saved_mperf = readin.mperf.whole;
+				per_cpu(msr_data, cpu).saved_mperf;
+	per_cpu(msr_data, cpu).saved_aperf = readin.aperf.whole;
+	per_cpu(msr_data, cpu).saved_mperf = readin.mperf.whole;
 
 #ifdef __i386__
 	/*
-- 
1.6.0.6

Re: [PATCH] x86, acpi_cpufreq: Fix the NULL pointer dereference in get_measured_perf

[Zhang, Yanmin]

On Wed, 2009-04-15 at 10:37 -0700, Pallipadi, Venkatesh wrote:
> Patch below fixes the problem. 


> Yanmin can you please verify.
It does work.


> Len please push this patch along to linus.
> 
> Thanks,
> Venki
> 
> 
> Fix for a regression that was introduced by earlier commit
> 
> commit 18b2646fe3babeb40b34a0c1751e0bf5adfdc64c
> Author: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
> Date:   Mon Apr 6 11:26:08 2009 -0700
> 
> Regression resulted in the below error happened on systems with
> software coordination where per_cpu acpi data will not be initiated for
> secondary CPUs in a P-state domain.
> 
> On Tue, 2009-04-14 at 23:01 -0700, Zhang, Yanmin wrote:
>  My machine hanged with kernel 2.6.30-rc2 when script read
> > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor.
> >
> > opps happens in get_measured_perf:
> >
> >         cur.aperf.whole = readin.aperf.whole -
> >                                 per_cpu(drv_data, cpu)->saved_aperf;
> >
> > Because per_cpu(drv_data, cpu)=NULL.
> >
> > So function get_measured_perf should check if (per_cpu(drv_data,
> > cpu)==NULL)
> > and return 0 if it's NULL.
> 
> --------------sys log------------------
> 
> BUG: unable to handle kernel NULL pointer dereference at
> 0000000000000020
> IP: [<ffffffff8021af75>] get_measured_perf+0x4a/0xf9
> PGD a7dd88067 PUD a7ccf5067 PMD 0
> Oops: 0000 [#1] SMP
> last sysfs file: /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
> CPU 0
> Modules linked in: video output
> Pid: 2091, comm: kondemand/0 Not tainted 2.6.30-rc2 #1 MP Server
> RIP: 0010:[<ffffffff8021af75>]  [<ffffffff8021af75>]
> get_measured_perf+0x4a/0xf9
> RSP: 0018:ffff880a7d56de20  EFLAGS: 00010246
> RAX: 0000000000000000 RBX: 00000046241a42b6 RCX: ffff88004d219000
> RDX: 000000000000b660 RSI: 0000000000000020 RDI: 0000000000000001
> RBP: ffff880a7f052000 R08: 00000046241a42b6 R09: ffffffff807639f0
> R10: 00000000ffffffea R11: ffffffff802207f4 R12: ffff880a7f052000
> R13: ffff88004d20e460 R14: 0000000000ddd5a6 R15: 0000000000000001
> FS:  0000000000000000(0000) GS:ffff88004d200000(0000)
> knlGS:0000000000000000
> CS:  0010 DS: 0018 ES: 0018 CR0: 000000008005003b
> CR2: 0000000000000020 CR3: 0000000a7f1bf000 CR4: 00000000000006e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> Process kondemand/0 (pid: 2091, threadinfo ffff880a7d56c000, task
> ffff880a7d4d18c0)
> Stack:
>  ffff880a7f052078 ffffffff803efd54 00000046241a42b6 000000462ffa9e95
>  0000000000000001 0000000000000001 00000000ffffffea ffffffff8064f41a
>  0000000000000012 0000000000000012 ffff880a7f052000 ffffffff80650547
> Call Trace:
>  [<ffffffff803efd54>] ? kobject_get+0x12/0x17
>  [<ffffffff8064f41a>] ? __cpufreq_driver_getavg+0x42/0x57
>  [<ffffffff80650547>] ? do_dbs_timer+0x147/0x272
>  [<ffffffff80650400>] ? do_dbs_timer+0x0/0x272
>  [<ffffffff802474ca>] ? worker_thread+0x15b/0x1f5
>  [<ffffffff8024a02c>] ? autoremove_wake_function+0x0/0x2e
>  [<ffffffff8024736f>] ? worker_thread+0x0/0x1f5
>  [<ffffffff80249f0d>] ? kthread+0x54/0x83
>  [<ffffffff8020c87a>] ? child_rip+0xa/0x20
>  [<ffffffff80249eb9>] ? kthread+0x0/0x83
>  [<ffffffff8020c870>] ? child_rip+0x0/0x20
> Code: 99 a6 03 00 31 c9 85 c0 0f 85 c3 00 00 00 89 df 4c 8b 44 24 10 48
> c7 c2 60 b6 00 00 48 8b 0c fd e0 30 a5 80 4c 89 c3 48 8b 04 0a <48> 2b
> 58 20 48 8b 44 24 18 48 89 1c 24 48 8b 34 0a 48 2b 46 28
> RIP  [<ffffffff8021af75>] get_measured_perf+0x4a/0xf9
>  RSP <ffff880a7d56de20>
> CR2: 0000000000000020
> ---[ end trace 2b8fac9a49e19ad4 ]---
> 
> Reported-by: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com>
> Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
> ---
>  arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c |   15 ++++++++++-----
>  1 files changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c b/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
> index 837c2c4..d722b8d 100644
> --- a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
> +++ b/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
> @@ -68,11 +68,16 @@ struct acpi_cpufreq_data {
>  	unsigned int max_freq;
>  	unsigned int resume;
>  	unsigned int cpu_feature;
> -	u64 saved_aperf, saved_mperf;
>  };
>  
>  static DEFINE_PER_CPU(struct acpi_cpufreq_data *, drv_data);
>  
> +struct acpi_msr_data {
> +	u64 saved_aperf, saved_mperf;
> +};
> +
> +static DEFINE_PER_CPU(struct acpi_msr_data, msr_data);
> +
>  DEFINE_TRACE(power_mark);
>  
>  /* acpi_perf_data is a pointer to percpu data. */
> @@ -281,11 +286,11 @@ static unsigned int get_measured_perf(struct cpufreq_policy *policy,
>  		return 0;
>  
>  	cur.aperf.whole = readin.aperf.whole -
> -				per_cpu(drv_data, cpu)->saved_aperf;
> +				per_cpu(msr_data, cpu).saved_aperf;
>  	cur.mperf.whole = readin.mperf.whole -
> -				per_cpu(drv_data, cpu)->saved_mperf;
> -	per_cpu(drv_data, cpu)->saved_aperf = readin.aperf.whole;
> -	per_cpu(drv_data, cpu)->saved_mperf = readin.mperf.whole;
> +				per_cpu(msr_data, cpu).saved_mperf;
> +	per_cpu(msr_data, cpu).saved_aperf = readin.aperf.whole;
> +	per_cpu(msr_data, cpu).saved_mperf = readin.mperf.whole;
>  
>  #ifdef __i386__
>  	/*

Re: [PATCH] x86, acpi_cpufreq: Fix the NULL pointer dereference in get_measured_perf

[Len Brown]

applied.

thanks,
Len Brown, Intel Open Source Technology Center