On Sun, Jun 14, 2020 at 12:00 PM Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote: > > Hi Andy, > > On Sun, Jun 14, 2020 at 11:43 AM Andy Shevchenko > <andy.shevchenko@xxxxxxxxx> wrote: > > On Sun, Jun 14, 2020 at 12:34 PM Andy Shevchenko > > <andy.shevchenko@xxxxxxxxx> wrote: > > > > > > On Sun, Jun 14, 2020 at 12:10 PM Wolfram Sang <wsa@xxxxxxxxxx> wrote: > > > > both in the I2C subsystem and also for Renesas drivers I maintain, I am > > > > starting to get boilerplate patches doing some pm_runtime_put_* variant > > > > because a failing pm_runtime_get is supposed to increase the ref > > > > counters? Really? This feels wrong and unintuitive to me. > > > > > > Yeah, that is a well known issue with PM (I even have for a long time > > > a coccinelle script, when I realized myself that there are a lot of > > > cases like this, but someone else discovered this recently, like > > > opening a can of worms). > > > > > > > I expect there > > > > has been a discussion around it but I couldn't find it. > > > > > > Rafael explained (again) recently this. I can't find it quickly, unfortunately. > > > > I _think_ this discussion, but may be it's simple another tentacle of > > the same octopus. > > https://patchwork.ozlabs.org/project/linux-tegra/patch/20200520095148.10995-1-dinghao.liu@xxxxxxxxxx/ > > Thanks, hadn't read that one! (so I was still at -1 from > http://sweng.the-davies.net/Home/rustys-api-design-manifesto ;-) > > So "pm_runtime_put_noidle()" is the (definitive?) one to pair with a > pm_runtime_get_sync() failure? If you bail out immediately on errors, then yes, it is. If you'd rather to something like ret = pm_runtime_get_sync(dev); if (ret < 0) goto fail; ... code depending on PM ... fail: pm_runtime_put_autosuspend(dev); then it will still work correctly. It actually doesn't matter which pm_runtime_put*() variant you call after a pm_runtime_get_sync() failure, but the _noidle() is the simplest one and it is sufficient. > > > > I wonder why we > > > > don't fix the code where the incremented refcount is expected for some > > > > reason. > > > > > > The main idea behind API that a lot of drivers do *not* check error > > > codes from runtime PM, so, we need to keep balance in case of > > > > > > pm_runtime_get(...); > > > ... > > > pm_runtime_put(...); > > I've always[*] considered a pm_runtime_get_sync() failure to be fatal > (or: cannot happen), and that there's nothing that can be done to > recover. Hence I never checked the function's return value. > Was that wrong? No, it wasn't. It is the right thing to do in the majority of cases. > [*] at least on Renesas SoCs with Clock and/or Power Domains. Cheers!
