[PATCH 4.19 072/140] cpufreq: powernv: fix stack bloat and hard limit on number of CPUs

Greg Kroah-Hartman
2019-12-16T18:04:18Z

From: John Hubbard <jhubbard@nvidia.com>

commit db0d32d84031188443e25edbd50a71a6e7ac5d1d upstream.

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 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/

The warning is due to putting 1024 bytes on the stack:

unsigned int chip[256];

...and it's also undesirable to have a hard limit on the number of
CPUs here.

Fix both problems by dynamically allocating based on num_possible_cpus,
as recommended by Michael Ellerman.

Fixes: 053819e0bf840 ("cpufreq: powernv: Handle throttling due to Pmax capping at chip level")
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Cc: 4.10+ <stable@vger.kernel.org> # 4.10+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/cpufreq/powernv-cpufreq.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)

--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c
@@ -1042,9 +1042,14 @@ static struct cpufreq_driver powernv_cpu

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(num_possible_cpus(), sizeof(*chip), GFP_KERNEL);
+ if (!chip)
+ return -ENOMEM;

for_each_possible_cpu(cpu) {
unsigned int id = cpu_to_chip_id(cpu);
@@ -1056,8 +1061,10 @@ 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];
@@ -1067,7 +1074,9 @@ 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)