| Message ID | 1843211.tdWV9SEqCh@kreacher (mailing list archive) |
|---|---|
| Headers | show |
| Series | ACPI: Get rid of the list of children in struct acpi_device | expand |
On Thu, Jun 09, 2022 at 03:44:27PM +0200, Rafael J. Wysocki wrote: > Hi All, > > Confusingly enough, the ACPI subsystem stores the information on the given ACPI > device's children in two places: as the list of children in struct acpi_device > and (as a result of device registration) in the list of children in the embedded > struct device. > > These two lists agree with each other most of the time, but not always (like in > error paths in some cases), and the list of children in struct acpi_device is > not generally safe to use without locking. In principle, it should always be > walked under acpi_device_lock, but in practice holding acpi_scan_lock is > sufficient for that too. However, its users may not know whether or not > they operate under acpi_scan_lock and at least in some cases it is not accessed > in a safe way (note that ACPI devices may go away as a result of hot-remove, > unlike OF nodes). Hmm... Does it true for DT overlays? Not an expert in DT overlays, though, adding Rob and Frank. > For this reason, it is better to consolidate the code that needs to walk the > children of an ACPI device which is the purpose of this patch series. > > Overall, it switches over all of the users of the list of children in struct > acpi_device to using helpers based on the driver core's mechanics and finally > drops that list, but some extra cleanups are done on the way. > > Please refer to the patch changelogs for details. I'm going to look the individual patches.
On Thu, Jun 09, 2022 at 03:44:27PM +0200, Rafael J. Wysocki wrote: > Hi All, > > Confusingly enough, the ACPI subsystem stores the information on the given ACPI > device's children in two places: as the list of children in struct acpi_device > and (as a result of device registration) in the list of children in the embedded > struct device. > > These two lists agree with each other most of the time, but not always (like in > error paths in some cases), and the list of children in struct acpi_device is > not generally safe to use without locking. In principle, it should always be > walked under acpi_device_lock, but in practice holding acpi_scan_lock is > sufficient for that too. However, its users may not know whether or not > they operate under acpi_scan_lock and at least in some cases it is not accessed > in a safe way (note that ACPI devices may go away as a result of hot-remove, > unlike OF nodes). > > For this reason, it is better to consolidate the code that needs to walk the > children of an ACPI device which is the purpose of this patch series. > > Overall, it switches over all of the users of the list of children in struct > acpi_device to using helpers based on the driver core's mechanics and finally > drops that list, but some extra cleanups are done on the way. > > Please refer to the patch changelogs for details. Cool series, thanks for doing that! You may add my Revieweed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> to all non-commented, by me, patches (excluding soundwire) and to ones where comment just about one line/two lines split (address them if you are okay, otherwise ignore those comments).
On Thu, Jun 9, 2022 at 5:57 PM Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote: > > On Thu, Jun 09, 2022 at 03:44:27PM +0200, Rafael J. Wysocki wrote: > > Hi All, > > > > Confusingly enough, the ACPI subsystem stores the information on the given ACPI > > device's children in two places: as the list of children in struct acpi_device > > and (as a result of device registration) in the list of children in the embedded > > struct device. > > > > These two lists agree with each other most of the time, but not always (like in > > error paths in some cases), and the list of children in struct acpi_device is > > not generally safe to use without locking. In principle, it should always be > > walked under acpi_device_lock, but in practice holding acpi_scan_lock is > > sufficient for that too. However, its users may not know whether or not > > they operate under acpi_scan_lock and at least in some cases it is not accessed > > in a safe way (note that ACPI devices may go away as a result of hot-remove, > > unlike OF nodes). > > > > For this reason, it is better to consolidate the code that needs to walk the > > children of an ACPI device which is the purpose of this patch series. > > > > Overall, it switches over all of the users of the list of children in struct > > acpi_device to using helpers based on the driver core's mechanics and finally > > drops that list, but some extra cleanups are done on the way. > > > > Please refer to the patch changelogs for details. > > Cool series, thanks for doing that! > > You may add my > Revieweed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> > to all non-commented, by me, patches (excluding soundwire) and to ones > where comment just about one line/two lines split (address them if you > are okay, otherwise ignore those comments). Thank you!
On 6/9/22 11:12, Andy Shevchenko wrote: > On Thu, Jun 09, 2022 at 03:44:27PM +0200, Rafael J. Wysocki wrote: >> Hi All, >> >> Confusingly enough, the ACPI subsystem stores the information on the given ACPI >> device's children in two places: as the list of children in struct acpi_device >> and (as a result of device registration) in the list of children in the embedded >> struct device. >> >> These two lists agree with each other most of the time, but not always (like in >> error paths in some cases), and the list of children in struct acpi_device is >> not generally safe to use without locking. In principle, it should always be >> walked under acpi_device_lock, but in practice holding acpi_scan_lock is >> sufficient for that too. However, its users may not know whether or not >> they operate under acpi_scan_lock and at least in some cases it is not accessed >> in a safe way (note that ACPI devices may go away as a result of hot-remove, > >> unlike OF nodes). > > Hmm... Does it true for DT overlays? Not an expert in DT overlays, though, > adding Rob and Frank. DT nodes can be removed. The devicetree code uses devtree_lock and of_mutex as needed for protection. -Frank > >> For this reason, it is better to consolidate the code that needs to walk the >> children of an ACPI device which is the purpose of this patch series. >> >> Overall, it switches over all of the users of the list of children in struct >> acpi_device to using helpers based on the driver core's mechanics and finally >> drops that list, but some extra cleanups are done on the way. >> >> Please refer to the patch changelogs for details. > > I'm going to look the individual patches. >