Messages in this thread | | | Date | Fri, 6 Jan 2023 17:08:27 +0800 | From | Tzung-Bi Shih <> | Subject | Re: [PATCH] platform/chromeos: cros_ec: Use per-device lockdep key |
| |
On Fri, Jan 06, 2023 at 12:55:37PM +0800, Chen-Yu Tsai wrote: > Lockdep reports a bogus possible deadlock on MT8192 Chromebooks due to > the following lock sequences: > > 1. lock(i2c_register_adapter) [1]; lock(&ec_dev->lock) > 2. lock(&ec_dev->lock); lock(prepare_lock); > > The actual dependency chains are much longer. The shortened version > looks somewhat like: > > 1. cros-ec-rpmsg on mtk-scp > ec_dev->lock -> prepare_lock > 2. In rt5682_i2c_probe() on native I2C bus: > prepare_lock -> regmap->lock -> (possibly) i2c_adapter->bus_lock > 3. In rt5682_i2c_probe() on native I2C bus: > regmap->lock -> i2c_adapter->bus_lock > 4. In sbs_probe() on cros-ec-i2c (passthrough) I2C bus on cros-ec > i2c_adapter->bus_lock -> ec_dev->lock > > While lockdep is correct that the shared lockdep classes have a circular > dependency, it is bogus because > > a) 2+3 happen on a native I2C bus > b) 4 happens on the actual EC on ChromeOS devices > c) 1 happens on the SCP coprocessor on MediaTek Chromebooks that just > happen to expose a cros-ec interface, but do not have a passthrough > I2C bus > > In short, the "dependencies" are actually on different devices.
Path of 4 looks weird to me.
Could you point out where sbs_probe() gets to acquire ec_dev->lock?
I may misunderstand: I thought there is no such I2C bus for passthrough from kernel's point of view (as the bus and devices behind the EC). See also [2].
[2]: https://elixir.bootlin.com/linux/v6.2-rc2/source/drivers/platform/chrome/cros_ec.c#L241
On a related note, for the commit title: s/chromeos/chrome/ if it gets chance to have next version.
| |