On 01-02-19, 12:07, Ranjani Sridharan wrote: > On Fri, 2019-02-01 at 23:42 +0530, Vinod Koul wrote: > > On 01-02-19, 11:22, Pierre-Louis Bossart wrote: > > > The ASoC core has for the longest time increased the module > > > reference > > > counts, even before the transition to the component model. This is > > > probably fine on most platforms, but it introduces a deadlock case > > > on > > > Intel devices with the Skylake and SOF drivers which cannot be > > > removed > > > due to their reference counts being modified by the core. > > > > > > In these 2 cases, the PCI or ACPI driver .probe creates a platform > > > device to let the machine driver .probe register the audio > > > card. Conversely the PCI or ACPI driver .remove will unregister the > > > platform device which results in the card being removed by the > > > machine > > > driver .remove. > > > > > > With ascii art, this can be represented as > > > > > > modprobe > > > snd_soc_skl/ > > > soc-pci-dev/sof-acpci-dev ----------> pci/acpi probe > > > ^ | > > > | ---------------| > > > | | | > > > | V V > > > increase register register machine > > > refcount component platform_device > > > ^ | > > > | | > > > | V > > > component <---- register card <---- probe > > > probe > > > > > > The issue is that by playing with the component's module reference > > > counts during the card registration, it's no longer possible to > > > remove > > > the module which controls the component. This can be shown, e.g. > > > with > > > the following error: > > > > > > root@plb-XPS-13-9350:~# lsmod | grep snd_soc_skl > > > snd_soc_skl 110592 1 > > > > > > root@plb-XPS-13-9350:~# rmmod snd_soc_skl > > > rmmod: ERROR: Module snd_soc_skl is in use > > > > Yup, that would be correct, the inuse is due to the fact the sound > > card > > is up and someone needs to unload the sound card to remove the > > reference. > > > > That can be done by doing the rmmod of machine driver first and IIRC > > that would remove the sound card and drop the reference and then > > snd_soc_skl can be unloaded. > > This doesnt seem to be the case though. The machine driver module > cannot be removed either because its refcnt is also > 0. At least this used to be the case when I used to try removal of modules on skl, doing the reverse of load order seemed to work for me back then. -- ~Vinod _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
