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 <jhubb...@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.b...@linux.vnet.ibm.com>
Cc: Preeti U Murthy <pre...@linux.vnet.ibm.com>
Cc: Viresh Kumar <viresh.ku...@linaro.org>
Cc: Rafael J. Wysocki <r...@rjwysocki.net>
Cc: linux...@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: John Hubbard <jhubb...@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
