The 'sensors -s' command in docker-platform-monitor rewrite incorrect set statements by default config.

[wadelnn]

Description

The "sensors -s" will load platform specific config (/etc/sensors.d/sensors.conf) first. And then load the default config (/etc/sensors3.conf). But some set statements will rewrite by default config. When use coammand sensors and it will show incorrect value or label.

Steps to reproduce the issue:

1. modify /usr/share/sonic/device/x86_64-ingrasys_s9100-r0/sensors.conf and search chip "w83795adg-*"
2. Add test code under chip "w83795adg-*" as follows:

set in12_min 3.3 * 0.95
set in12_max 3.3 * 1.05

3. Save the file and reboot
4. Login and execute command sensors

Describe the results you received:
The 3.3V min and max value still between 3.3 * 0.90 and 3.3 * 1.10

Describe the results you expected:
The 3.3V min value is 3.3 * 0.95 and max value is 3.3 * 1.05

Additional information you deem important (e.g. issue happens only occasionally):

I think this issue is related by this code:
https://github.com/Azure/sonic-buildimage/blob/f49cac086f8421bf5d76a4798c4906700a322a50/dockers/docker-platform-monitor/lm-sensors.sh#L6

We fixed this issue by replace lm-sensors.sh line 6 as follows:

if [ -e /etc/sensors.d/sensors.conf ]; then
    /usr/bin/sensors -s -c /etc/sensors.d/sensors.conf > /dev/null 2>&1
else
    /usr/bin/sensors -s > /dev/null 2>&1
fi

And this code will avoid rewrite default config.

[jleveque]

I was able to confirm this on a different platform. This appears to be a bug in lm-sensors. Thanks for catching this.

Looking at sensors -s with strace, the config files appear to get loaded in the proper order, yet the default values do not appear to get overridden by the platform-specific ones.

open("/etc/sensors3.conf", O_RDONLY)    = 3
ioctl(3, SNDCTL_TMR_TIMEBASE or SNDRV_TIMER_IOCTL_NEXT_DEVICE or TCGETS, 0x7ffd70c2ef80) = -1 ENOTTY (Inappropriate ioctl for device)
fstat(3, {st_mode=S_IFREG|0644, st_size=10344, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fd940d57000
read(3, "# libsensors configuration file\n"..., 8192) = 8192
read(3, " label in4 \"+12V\"\n    label in5 "..., 8192) = 2152
read(3, "", 4096)                       = 0
read(3, "", 8192)                       = 0
ioctl(3, SNDCTL_TMR_TIMEBASE or SNDRV_TIMER_IOCTL_NEXT_DEVICE or TCGETS, 0x7ffd70c2d910) = -1 ENOTTY (Inappropriate ioctl for device)
close(3)                                = 0
munmap(0x7fd940d57000, 4096)            = 0
openat(AT_FDCWD, "/etc/sensors.d", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 3
getdents(3, /* 4 entries */, 32768)     = 112
getdents(3, /* 0 entries */, 32768)     = 0
close(3)                                = 0
stat("/etc/sensors.d/sensors.conf", {st_mode=S_IFREG|0644, st_size=1449, ...}) = 0
open("/etc/sensors.d/sensors.conf", O_RDONLY) = 3
ioctl(3, SNDCTL_TMR_TIMEBASE or SNDRV_TIMER_IOCTL_NEXT_DEVICE or TCGETS, 0x7ffd70c2de70) = -1 ENOTTY (Inappropriate ioctl for device)
fstat(3, {st_mode=S_IFREG|0644, st_size=1449, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fd940d57000
read(3, "# libsensors configuration file\n"..., 8192) = 1449
read(3, "", 4096)                       = 0
read(3, "", 8192)                       = 0
ioctl(3, SNDCTL_TMR_TIMEBASE or SNDRV_TIMER_IOCTL_NEXT_DEVICE or TCGETS, 0x7ffd70c2c800) = -1 ENOTTY (Inappropriate ioctl for device)
close(3)                                = 0
munmap(0x7fd940d57000, 4096)            = 0

I am creating a pull request using your workaround for the time being.