* [PATCH] cpufreq: powernv: fix stack bloat and NR_CPUS limitation
@ 2019-10-18 0:04 John Hubbard
2019-10-18 4:27 ` Viresh Kumar
0 siblings, 1 reply; 6+ messages in thread
From: John Hubbard @ 2019-10-18 0:04 UTC (permalink / raw)
To: Shilpasri G Bhat
Cc: LKML, John Hubbard, Preeti U Murthy, Viresh Kumar,
Rafael J . Wysocki, linux-pm, 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>
---
Hi,
I have only compile-tested this, so I would appreciate if anyone
could do a basic runtime test on it. But (famous last words) it
seems simple enough that I'm confident it's correct. oh boy. :)
thanks,
John Hubbard
NVIDIA
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..78e04402125f 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(int), GFP_KERNEL);
+ if (!chips)
+ 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] cpufreq: powernv: fix stack bloat and NR_CPUS limitation
2019-10-18 0:04 [PATCH] cpufreq: powernv: fix stack bloat and NR_CPUS limitation John Hubbard
@ 2019-10-18 4:27 ` Viresh Kumar
2019-10-18 4:34 ` John Hubbard
0 siblings, 1 reply; 6+ messages in thread
From: Viresh Kumar @ 2019-10-18 4:27 UTC (permalink / raw)
To: John Hubbard
Cc: Shilpasri G Bhat, LKML, Preeti U Murthy, Rafael J . Wysocki,
linux-pm, linuxppc-dev
On 17-10-19, 17:04, 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=]
How come we are catching this warning after 4 years ?
>
> 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>
> ---
>
> Hi,
>
> I have only compile-tested this, so I would appreciate if anyone
> could do a basic runtime test on it. But (famous last words) it
> seems simple enough that I'm confident it's correct. oh boy. :)
>
> thanks,
> John Hubbard
> NVIDIA
>
> 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..78e04402125f 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(int), GFP_KERNEL);
sizeof(*chip)
> + if (!chips)
(!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
--
viresh
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] cpufreq: powernv: fix stack bloat and NR_CPUS limitation
2019-10-18 4:27 ` Viresh Kumar
@ 2019-10-18 4:34 ` John Hubbard
2019-10-18 4:38 ` Viresh Kumar
0 siblings, 1 reply; 6+ messages in thread
From: John Hubbard @ 2019-10-18 4:34 UTC (permalink / raw)
To: Viresh Kumar
Cc: Shilpasri G Bhat, LKML, Preeti U Murthy, Rafael J . Wysocki,
linux-pm, linuxppc-dev
On 10/17/19 9:27 PM, Viresh Kumar wrote:
> On 17-10-19, 17:04, 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=]
>
> How come we are catching this warning after 4 years ?
>
Newer compilers. And btw, I don't spend a lot of time in powerpc
code, so I just recently ran this, and I guess everyone has been on less
new compilers so far, it seems.
I used a gcc 8.1 cross compiler in this case:
$ $ /blue_exp/kernel/cross-compilers/powerpc64/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-gcc -v
Using built-in specs.
COLLECT_GCC=/blue_exp/kernel/cross-compilers/powerpc64/gcc-8.1.0-nolibc/powerpc64-linux/bin/powerpc64-linux-gcc
COLLECT_LTO_WRAPPER=/home/jhubbard/blue_exp/kernel/cross-compilers/powerpc64/gcc-8.1.0-nolibc/powerpc64-linux/bin/../libexec/gcc/powerpc64-linux/8.1.0/lto-wrapper
Target: powerpc64-linux
Configured with: /home/arnd/git/gcc/configure --target=powerpc64-linux --enable-targets=all --prefix=/home/arnd/cross/x86_64/gcc-8.1.0-nolibc/powerpc64-linux --enable-languages=c --without-headers --disable-bootstrap --disable-nls --disable-threads --disable-shared --disable-libmudflap --disable-libssp --disable-libgomp --disable-decimal-float --disable-libquadmath --disable-libatomic --disable-libcc1 --disable-libmpx --enable-checking=release
Thread model: single
gcc version 8.1.0 (GCC)
thanks,
John Hubbard
NVIDIA
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] cpufreq: powernv: fix stack bloat and NR_CPUS limitation
2019-10-18 4:34 ` John Hubbard
@ 2019-10-18 4:38 ` Viresh Kumar
2019-10-18 4:41 ` John Hubbard
0 siblings, 1 reply; 6+ messages in thread
From: Viresh Kumar @ 2019-10-18 4:38 UTC (permalink / raw)
To: John Hubbard
Cc: Shilpasri G Bhat, LKML, Rafael J . Wysocki, linux-pm, linuxppc-dev
On 17-10-19, 21:34, John Hubbard wrote:
> On 10/17/19 9:27 PM, Viresh Kumar wrote:
> > On 17-10-19, 17:04, 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=]
> >
> > How come we are catching this warning after 4 years ?
> >
>
> Newer compilers. And btw, I don't spend a lot of time in powerpc
> code, so I just recently ran this, and I guess everyone has been on less
> new compilers so far, it seems.
>
> I used a gcc 8.1 cross compiler in this case:
Hmm, okay.
I hope you haven't missed my actual review comments on your patch,
just wanted to make sure we don't end up waiting for each other
indefinitely here :)
--
viresh
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] cpufreq: powernv: fix stack bloat and NR_CPUS limitation
2019-10-18 4:38 ` Viresh Kumar
@ 2019-10-18 4:41 ` John Hubbard
2019-10-18 4:50 ` Viresh Kumar
0 siblings, 1 reply; 6+ messages in thread
From: John Hubbard @ 2019-10-18 4:41 UTC (permalink / raw)
To: Viresh Kumar
Cc: Shilpasri G Bhat, LKML, Rafael J . Wysocki, linux-pm, linuxppc-dev
On 10/17/19 9:38 PM, Viresh Kumar wrote:
> On 17-10-19, 21:34, John Hubbard wrote:
>> On 10/17/19 9:27 PM, Viresh Kumar wrote:
>>> On 17-10-19, 17:04, 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=]
>>>
>>> How come we are catching this warning after 4 years ?
>>>
>>
>> Newer compilers. And btw, I don't spend a lot of time in powerpc
>> code, so I just recently ran this, and I guess everyone has been on less
>> new compilers so far, it seems.
>>
>> I used a gcc 8.1 cross compiler in this case:
>
> Hmm, okay.
>
> I hope you haven't missed my actual review comments on your patch,
> just wanted to make sure we don't end up waiting for each other
> indefinitely here :)
>
Ha, I did overlook those. It's late around here, I guess. :)
I'll send a v2 with those changes.
thanks,
John Hubbard
NVIDIA
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] cpufreq: powernv: fix stack bloat and NR_CPUS limitation
2019-10-18 4:41 ` John Hubbard
@ 2019-10-18 4:50 ` Viresh Kumar
0 siblings, 0 replies; 6+ messages in thread
From: Viresh Kumar @ 2019-10-18 4:50 UTC (permalink / raw)
To: John Hubbard
Cc: Shilpasri G Bhat, LKML, Rafael J . Wysocki, linux-pm, linuxppc-dev
On 17-10-19, 21:41, John Hubbard wrote:
> On 10/17/19 9:38 PM, Viresh Kumar wrote:
> > On 17-10-19, 21:34, John Hubbard wrote:
> >> On 10/17/19 9:27 PM, Viresh Kumar wrote:
> >>> On 17-10-19, 17:04, 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=]
> >>>
> >>> How come we are catching this warning after 4 years ?
> >>>
> >>
> >> Newer compilers. And btw, I don't spend a lot of time in powerpc
> >> code, so I just recently ran this, and I guess everyone has been on less
> >> new compilers so far, it seems.
> >>
> >> I used a gcc 8.1 cross compiler in this case:
> >
> > Hmm, okay.
> >
> > I hope you haven't missed my actual review comments on your patch,
> > just wanted to make sure we don't end up waiting for each other
> > indefinitely here :)
> >
>
> Ha, I did overlook those. It's late around here, I guess. :)
Good that I reminded you then :)
--
viresh
^ permalink raw reply [flat|nested] 6+ messages in thread
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2019-10-18 0:04 [PATCH] cpufreq: powernv: fix stack bloat and NR_CPUS limitation John Hubbard
2019-10-18 4:27 ` Viresh Kumar
2019-10-18 4:34 ` John Hubbard
2019-10-18 4:38 ` Viresh Kumar
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2019-10-18 4:50 ` Viresh Kumar
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