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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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7231ed1a81
Before this commit, the following would happen:
a) acpi_video_get_backlight_type() gets called
b) acpi_video_get_backlight_type() calls acpi_video_init_backlight_type()
c) acpi_video_init_backlight_type() locks its function static init_mutex
d) acpi_video_init_backlight_type() calls backlight_register_notifier()
e) backlight_register_notifier() takes its notifier-chain lock
And when the backlight notifier chain gets called we've:
1) blocking_notifier_call_chain() gets called
2) blocking_notifier_call_chain() takes the notifier-chain lock
3) blocking_notifier_call_chain() calls acpi_video_backlight_notify()
4) acpi_video_backlight_notify() calls acpi_video_get_backlight_type()
5) acpi_video_get_backlight_type() calls acpi_video_init_backlight_type()
6) acpi_video_init_backlight_type() locks its function static init_mutex
So in the first call sequence we have:
a) init_mutex gets locked
b) notifier-chain gets locked
and in the second call sequence we have:
1) notifier-chain gets locked
2) init_mutex gets locked
And we've a circular locking dependency. This specific locking dependency
is fixable without using the big hammer otherwise known as a workqueue,
but further analysis shows a similar problem with the backlight notifier
chain lock vs register_count_mutex from drivers/acpi/acpi_video.c,
and fixing that becomes problematic.
So this commit simply fixes this with the big hammer, performance
wise this is a non issue as we expect the work to get scheduled
exactly zero or one times during normal system use.
Fixes:
|
||
|---|---|---|
| .. | ||
| acpica | ||
| apei | ||
| pmic | ||
| ac.c | ||
| acpi_apd.c | ||
| acpi_cmos_rtc.c | ||
| acpi_extlog.c | ||
| acpi_ipmi.c | ||
| acpi_lpat.c | ||
| acpi_lpss.c | ||
| acpi_memhotplug.c | ||
| acpi_pad.c | ||
| acpi_platform.c | ||
| acpi_pnp.c | ||
| acpi_processor.c | ||
| acpi_video.c | ||
| battery.c | ||
| battery.h | ||
| bgrt.c | ||
| blacklist.c | ||
| bus.c | ||
| button.c | ||
| cm_sbs.c | ||
| container.c | ||
| custom_method.c | ||
| debugfs.c | ||
| device_pm.c | ||
| dock.c | ||
| ec_sys.c | ||
| ec.c | ||
| event.c | ||
| fan.c | ||
| glue.c | ||
| gsi.c | ||
| hed.c | ||
| int340x_thermal.c | ||
| internal.h | ||
| ioapic.c | ||
| Kconfig | ||
| Makefile | ||
| nfit.c | ||
| nfit.h | ||
| numa.c | ||
| nvs.c | ||
| osl.c | ||
| pci_irq.c | ||
| pci_link.c | ||
| pci_root.c | ||
| pci_slot.c | ||
| power.c | ||
| proc.c | ||
| processor_core.c | ||
| processor_driver.c | ||
| processor_idle.c | ||
| processor_pdc.c | ||
| processor_perflib.c | ||
| processor_thermal.c | ||
| processor_throttling.c | ||
| property.c | ||
| reboot.c | ||
| resource.c | ||
| sbs.c | ||
| sbshc.c | ||
| sbshc.h | ||
| scan.c | ||
| sleep.c | ||
| sleep.h | ||
| sysfs.c | ||
| tables.c | ||
| thermal.c | ||
| utils.c | ||
| video_detect.c | ||
| wakeup.c | ||