* [PATCH v2] cpufreq: powernv: fix stack bloat and NR_CPUS limitation
@ 2019-10-18 4:55 John Hubbard
2019-10-18 5:07 ` Viresh Kumar
2019-10-31 2:39 ` Michael Ellerman
0 siblings, 2 replies; 6+ messages in thread
From: John Hubbard @ 2019-10-18 4:55 UTC (permalink / raw)
To: Viresh Kumar, Shilpasri G Bhat
Cc: linux-pm, John Hubbard, Rafael J . Wysocki, LKML,
Preeti U Murthy, linuxppc-dev
The following build warning occurred on powerpc 64-bit builds:
drivers/cpufreq/powernv-cpufreq.c: In function 'init_chip_info':
drivers/cpufreq/powernv-cpufreq.c:1070:1: warning: the frame size of 1040 bytes is larger than 1024 bytes [-Wframe-larger-than=]
This is due to putting 1024 bytes on the stack:
unsigned int chip[256];
...and while looking at this, it also has a bug: it fails with a stack
overrun, if CONFIG_NR_CPUS > 256.
Fix both problems by dynamically allocating based on CONFIG_NR_CPUS.
Fixes: 053819e0bf840 ("cpufreq: powernv: Handle throttling due to Pmax capping at chip level")
Cc: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: linux-pm@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
Changes since v1: includes Viresh's review commit fixes.
drivers/cpufreq/powernv-cpufreq.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
index 6061850e59c9..5b2e968cb5ea 100644
--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c
@@ -1041,9 +1041,14 @@ static struct cpufreq_driver powernv_cpufreq_driver = {
static int init_chip_info(void)
{
- unsigned int chip[256];
+ unsigned int *chip;
unsigned int cpu, i;
unsigned int prev_chip_id = UINT_MAX;
+ int ret = 0;
+
+ chip = kcalloc(CONFIG_NR_CPUS, sizeof(*chip), GFP_KERNEL);
+ if (!chip)
+ return -ENOMEM;
for_each_possible_cpu(cpu) {
unsigned int id = cpu_to_chip_id(cpu);
@@ -1055,8 +1060,10 @@ static int init_chip_info(void)
}
chips = kcalloc(nr_chips, sizeof(struct chip), GFP_KERNEL);
- if (!chips)
- return -ENOMEM;
+ if (!chips) {
+ ret = -ENOMEM;
+ goto free_and_return;
+ }
for (i = 0; i < nr_chips; i++) {
chips[i].id = chip[i];
@@ -1066,7 +1073,9 @@ static int init_chip_info(void)
per_cpu(chip_info, cpu) = &chips[i];
}
- return 0;
+free_and_return:
+ kfree(chip);
+ return ret;
}
static inline void clean_chip_info(void)
--
2.23.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v2] cpufreq: powernv: fix stack bloat and NR_CPUS limitation
2019-10-18 4:55 [PATCH v2] cpufreq: powernv: fix stack bloat and NR_CPUS limitation John Hubbard
@ 2019-10-18 5:07 ` Viresh Kumar
2019-10-28 15:26 ` Rafael J. Wysocki
2019-10-31 2:39 ` Michael Ellerman
1 sibling, 1 reply; 6+ messages in thread
From: Viresh Kumar @ 2019-10-18 5:07 UTC (permalink / raw)
To: John Hubbard
Cc: linux-pm, Rafael J . Wysocki, LKML, Shilpasri G Bhat,
Preeti U Murthy, linuxppc-dev
On 17-10-19, 21:55, John Hubbard wrote:
> The following build warning occurred on powerpc 64-bit builds:
>
> drivers/cpufreq/powernv-cpufreq.c: In function 'init_chip_info':
> drivers/cpufreq/powernv-cpufreq.c:1070:1: warning: the frame size of 1040 bytes is larger than 1024 bytes [-Wframe-larger-than=]
>
> This is due to putting 1024 bytes on the stack:
>
> unsigned int chip[256];
>
> ...and while looking at this, it also has a bug: it fails with a stack
> overrun, if CONFIG_NR_CPUS > 256.
>
> Fix both problems by dynamically allocating based on CONFIG_NR_CPUS.
>
> Fixes: 053819e0bf840 ("cpufreq: powernv: Handle throttling due to Pmax capping at chip level")
> Cc: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
> Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
> Cc: Viresh Kumar <viresh.kumar@linaro.org>
> Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
> Cc: linux-pm@vger.kernel.org
> Cc: linuxppc-dev@lists.ozlabs.org
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
> ---
>
> Changes since v1: includes Viresh's review commit fixes.
>
> drivers/cpufreq/powernv-cpufreq.c | 17 +++++++++++++----
> 1 file changed, 13 insertions(+), 4 deletions(-)
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
--
viresh
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2] cpufreq: powernv: fix stack bloat and NR_CPUS limitation
2019-10-18 5:07 ` Viresh Kumar
@ 2019-10-28 15:26 ` Rafael J. Wysocki
0 siblings, 0 replies; 6+ messages in thread
From: Rafael J. Wysocki @ 2019-10-28 15:26 UTC (permalink / raw)
To: Viresh Kumar
Cc: linux-pm, John Hubbard, LKML, Shilpasri G Bhat, Preeti U Murthy,
linuxppc-dev
On Friday, October 18, 2019 7:07:12 AM CET Viresh Kumar wrote:
> On 17-10-19, 21:55, John Hubbard wrote:
> > The following build warning occurred on powerpc 64-bit builds:
> >
> > drivers/cpufreq/powernv-cpufreq.c: In function 'init_chip_info':
> > drivers/cpufreq/powernv-cpufreq.c:1070:1: warning: the frame size of 1040 bytes is larger than 1024 bytes [-Wframe-larger-than=]
> >
> > This is due to putting 1024 bytes on the stack:
> >
> > unsigned int chip[256];
> >
> > ...and while looking at this, it also has a bug: it fails with a stack
> > overrun, if CONFIG_NR_CPUS > 256.
> >
> > Fix both problems by dynamically allocating based on CONFIG_NR_CPUS.
> >
> > Fixes: 053819e0bf840 ("cpufreq: powernv: Handle throttling due to Pmax capping at chip level")
> > Cc: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
> > Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
> > Cc: Viresh Kumar <viresh.kumar@linaro.org>
> > Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
> > Cc: linux-pm@vger.kernel.org
> > Cc: linuxppc-dev@lists.ozlabs.org
> > Signed-off-by: John Hubbard <jhubbard@nvidia.com>
> > ---
> >
> > Changes since v1: includes Viresh's review commit fixes.
> >
> > drivers/cpufreq/powernv-cpufreq.c | 17 +++++++++++++----
> > 1 file changed, 13 insertions(+), 4 deletions(-)
>
> Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
>
>
Applying as 5.5 material, thanks!
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2] cpufreq: powernv: fix stack bloat and NR_CPUS limitation
2019-10-18 4:55 [PATCH v2] cpufreq: powernv: fix stack bloat and NR_CPUS limitation John Hubbard
2019-10-18 5:07 ` Viresh Kumar
@ 2019-10-31 2:39 ` Michael Ellerman
2019-10-31 5:17 ` John Hubbard
1 sibling, 1 reply; 6+ messages in thread
From: Michael Ellerman @ 2019-10-31 2:39 UTC (permalink / raw)
To: John Hubbard, Viresh Kumar, Shilpasri G Bhat
Cc: linux-pm, John Hubbard, Rafael J . Wysocki, LKML,
Preeti U Murthy, linuxppc-dev
Hi John,
Sorry I didn't reply to this sooner, too many patches :/
John Hubbard <jhubbard@nvidia.com> writes:
> The following build warning occurred on powerpc 64-bit builds:
>
> drivers/cpufreq/powernv-cpufreq.c: In function 'init_chip_info':
> drivers/cpufreq/powernv-cpufreq.c:1070:1: warning: the frame size of 1040 bytes is larger than 1024 bytes [-Wframe-larger-than=]
Oddly I don't see that warning in my builds, eg with GCC9:
https://travis-ci.org/linuxppc/linux/jobs/604870722
> This is due to putting 1024 bytes on the stack:
>
> unsigned int chip[256];
>
> ...and while looking at this, it also has a bug: it fails with a stack
> overrun, if CONFIG_NR_CPUS > 256.
It _probably_ doesn't, because it only increments the index when the
chip_id of the CPU changes, ie. it doesn't create a chip for every CPU.
But I agree it's flaky the way it's written.
> Fix both problems by dynamically allocating based on CONFIG_NR_CPUS.
Shouldn't it use num_possible_cpus() ?
Given the for loop is over possible CPUs that seems like the upper
bound. In practice it should be lower because some CPUs will share a
chip.
cheers
> Fixes: 053819e0bf840 ("cpufreq: powernv: Handle throttling due to Pmax capping at chip level")
> Cc: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
> Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
> Cc: Viresh Kumar <viresh.kumar@linaro.org>
> Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
> Cc: linux-pm@vger.kernel.org
> Cc: linuxppc-dev@lists.ozlabs.org
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
> ---
>
> Changes since v1: includes Viresh's review commit fixes.
>
> drivers/cpufreq/powernv-cpufreq.c | 17 +++++++++++++----
> 1 file changed, 13 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
> index 6061850e59c9..5b2e968cb5ea 100644
> --- a/drivers/cpufreq/powernv-cpufreq.c
> +++ b/drivers/cpufreq/powernv-cpufreq.c
> @@ -1041,9 +1041,14 @@ static struct cpufreq_driver powernv_cpufreq_driver = {
>
> static int init_chip_info(void)
> {
> - unsigned int chip[256];
> + unsigned int *chip;
> unsigned int cpu, i;
> unsigned int prev_chip_id = UINT_MAX;
> + int ret = 0;
> +
> + chip = kcalloc(CONFIG_NR_CPUS, sizeof(*chip), GFP_KERNEL);
> + if (!chip)
> + return -ENOMEM;
>
> for_each_possible_cpu(cpu) {
> unsigned int id = cpu_to_chip_id(cpu);
> @@ -1055,8 +1060,10 @@ static int init_chip_info(void)
> }
>
> chips = kcalloc(nr_chips, sizeof(struct chip), GFP_KERNEL);
> - if (!chips)
> - return -ENOMEM;
> + if (!chips) {
> + ret = -ENOMEM;
> + goto free_and_return;
> + }
>
> for (i = 0; i < nr_chips; i++) {
> chips[i].id = chip[i];
> @@ -1066,7 +1073,9 @@ static int init_chip_info(void)
> per_cpu(chip_info, cpu) = &chips[i];
> }
>
> - return 0;
> +free_and_return:
> + kfree(chip);
> + return ret;
> }
>
> static inline void clean_chip_info(void)
> --
> 2.23.0
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2] cpufreq: powernv: fix stack bloat and NR_CPUS limitation
2019-10-31 2:39 ` Michael Ellerman
@ 2019-10-31 5:17 ` John Hubbard
2019-11-06 3:35 ` Michael Ellerman
0 siblings, 1 reply; 6+ messages in thread
From: John Hubbard @ 2019-10-31 5:17 UTC (permalink / raw)
To: Michael Ellerman, Viresh Kumar, Shilpasri G Bhat
Cc: Preeti U Murthy, linuxppc-dev, Rafael J . Wysocki, LKML, linux-pm
On 10/30/19 7:39 PM, Michael Ellerman wrote:
> Hi John,
>
> Sorry I didn't reply to this sooner, too many patches :/
>
> John Hubbard <jhubbard@nvidia.com> writes:
>> The following build warning occurred on powerpc 64-bit builds:
>>
>> drivers/cpufreq/powernv-cpufreq.c: In function 'init_chip_info':
>> drivers/cpufreq/powernv-cpufreq.c:1070:1: warning: the frame size of 1040 bytes is larger than 1024 bytes [-Wframe-larger-than=]
>
> Oddly I don't see that warning in my builds, eg with GCC9:
>
> https://travis-ci.org/linuxppc/linux/jobs/604870722
This is with a cross-compiler based on gcc 8.1.0, which I got from:
https://mirrors.edge.kernel.org/pub/tools/crosstool/files/bin/x86_64/8.1.0/
I'll put that in the v3 commit description.
>
>> This is due to putting 1024 bytes on the stack:
>>
>> unsigned int chip[256];
>>
>> ...and while looking at this, it also has a bug: it fails with a stack
>> overrun, if CONFIG_NR_CPUS > 256.
>
> It _probably_ doesn't, because it only increments the index when the
> chip_id of the CPU changes, ie. it doesn't create a chip for every CPU.
> But I agree it's flaky the way it's written.
I'll soften up the wording accordingly.
>
>> Fix both problems by dynamically allocating based on CONFIG_NR_CPUS.
>
> Shouldn't it use num_possible_cpus() ?
>
> Given the for loop is over possible CPUs that seems like the upper
> bound. In practice it should be lower because some CPUs will share a
> chip.
>
OK, I see, that's more consistent with the code, I'll change to that.
thanks,
--
John Hubbard
NVIDIA
>
>
>> Fixes: 053819e0bf840 ("cpufreq: powernv: Handle throttling due to Pmax capping at chip level")
>> Cc: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
>> Cc: Preeti U Murthy <preeti@linux.vnet.ibm.com>
>> Cc: Viresh Kumar <viresh.kumar@linaro.org>
>> Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
>> Cc: linux-pm@vger.kernel.org
>> Cc: linuxppc-dev@lists.ozlabs.org
>> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
>> ---
>>
>> Changes since v1: includes Viresh's review commit fixes.
>>
>> drivers/cpufreq/powernv-cpufreq.c | 17 +++++++++++++----
>> 1 file changed, 13 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
>> index 6061850e59c9..5b2e968cb5ea 100644
>> --- a/drivers/cpufreq/powernv-cpufreq.c
>> +++ b/drivers/cpufreq/powernv-cpufreq.c
>> @@ -1041,9 +1041,14 @@ static struct cpufreq_driver powernv_cpufreq_driver = {
>>
>> static int init_chip_info(void)
>> {
>> - unsigned int chip[256];
>> + unsigned int *chip;
>> unsigned int cpu, i;
>> unsigned int prev_chip_id = UINT_MAX;
>> + int ret = 0;
>> +
>> + chip = kcalloc(CONFIG_NR_CPUS, sizeof(*chip), GFP_KERNEL);
>> + if (!chip)
>> + return -ENOMEM;
>>
>> for_each_possible_cpu(cpu) {
>> unsigned int id = cpu_to_chip_id(cpu);
>> @@ -1055,8 +1060,10 @@ static int init_chip_info(void)
>> }
>>
>> chips = kcalloc(nr_chips, sizeof(struct chip), GFP_KERNEL);
>> - if (!chips)
>> - return -ENOMEM;
>> + if (!chips) {
>> + ret = -ENOMEM;
>> + goto free_and_return;
>> + }
>>
>> for (i = 0; i < nr_chips; i++) {
>> chips[i].id = chip[i];
>> @@ -1066,7 +1073,9 @@ static int init_chip_info(void)
>> per_cpu(chip_info, cpu) = &chips[i];
>> }
>>
>> - return 0;
>> +free_and_return:
>> + kfree(chip);
>> + return ret;
>> }
>>
>> static inline void clean_chip_info(void)
>> --
>> 2.23.0
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2] cpufreq: powernv: fix stack bloat and NR_CPUS limitation
2019-10-31 5:17 ` John Hubbard
@ 2019-11-06 3:35 ` Michael Ellerman
0 siblings, 0 replies; 6+ messages in thread
From: Michael Ellerman @ 2019-11-06 3:35 UTC (permalink / raw)
To: John Hubbard, Viresh Kumar, Shilpasri G Bhat
Cc: Preeti U Murthy, linuxppc-dev, Rafael J . Wysocki, LKML, linux-pm
John Hubbard <jhubbard@nvidia.com> writes:
> On 10/30/19 7:39 PM, Michael Ellerman wrote:
>> Hi John,
>>
>> Sorry I didn't reply to this sooner, too many patches :/
>>
>> John Hubbard <jhubbard@nvidia.com> writes:
>>> The following build warning occurred on powerpc 64-bit builds:
>>>
>>> drivers/cpufreq/powernv-cpufreq.c: In function 'init_chip_info':
>>> drivers/cpufreq/powernv-cpufreq.c:1070:1: warning: the frame size of 1040 bytes is larger than 1024 bytes [-Wframe-larger-than=]
>>
>> Oddly I don't see that warning in my builds, eg with GCC9:
>>
>> https://travis-ci.org/linuxppc/linux/jobs/604870722
>
> This is with a cross-compiler based on gcc 8.1.0, which I got from:
> https://mirrors.edge.kernel.org/pub/tools/crosstool/files/bin/x86_64/8.1.0/
>
> I'll put that in the v3 commit description.
>
>>
>>> This is due to putting 1024 bytes on the stack:
>>>
>>> unsigned int chip[256];
>>>
>>> ...and while looking at this, it also has a bug: it fails with a stack
>>> overrun, if CONFIG_NR_CPUS > 256.
>>
>> It _probably_ doesn't, because it only increments the index when the
>> chip_id of the CPU changes, ie. it doesn't create a chip for every CPU.
>> But I agree it's flaky the way it's written.
>
> I'll soften up the wording accordingly.
>
>>
>>> Fix both problems by dynamically allocating based on CONFIG_NR_CPUS.
>>
>> Shouldn't it use num_possible_cpus() ?
>>
>> Given the for loop is over possible CPUs that seems like the upper
>> bound. In practice it should be lower because some CPUs will share a
>> chip.
>>
>
> OK, I see, that's more consistent with the code, I'll change to that.
Thanks.
cheers
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2019-11-06 3:37 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2019-10-18 4:55 [PATCH v2] cpufreq: powernv: fix stack bloat and NR_CPUS limitation John Hubbard
2019-10-18 5:07 ` Viresh Kumar
2019-10-28 15:26 ` Rafael J. Wysocki
2019-10-31 2:39 ` Michael Ellerman
2019-10-31 5:17 ` John Hubbard
2019-11-06 3:35 ` Michael Ellerman
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