On Tue, 23 Mar 2021 19:25:53 +0100, Andrey Grodzovsky wrote: > > >> This will cover IOCTLs and any > >> mmapped accesses i guess. Interrupts we discussed above. What above any > >> possible background kernel work going on in dedicated threads or work > >> items ? Any pointers there what should be blocked and waited for ? > > > > An alternative idea would be the analogy of the system suspend / > > resume. That is, we forcibly suspend the devices at first somehow, > > and also restricts the further accesses by some way. Then do remap, > > But that the point I guess, how you block further accesses without those > big locks, during S3 i believe user mode gets suspended before the > driver and so you don't need to worry about concurrent IOCTLs when going > through suspend sequence ALSA core still has some legacy card-level power management code, which was introduced many years ago at the time we still managed the power state via an extra ioctl (hence working individually from the base PM code), and a few pieces are still effective for this kind of purposes. Through a quick glance, a couple of places need band-aids, but the rest should work. A bit more difficult problem is the floating control API calls. The get/put calls might be still in flight when we perform the PCI rescan. This has to be filtered out additionally. Below are a patch series I cooked quickly. Totally untested, just checked the compilation. The first patch is a fix I'll merge in anyway, while the rest are RFC. thanks, Takashi
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0001-ALSA-hda-Re-add-dropped-snd_poewr_change_state-calls.patch
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0002-ALSA-control-Add-power-state-check-commonly-for-ioct.patch
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0003-ALSA-control-Drop-superfluous-snd_power_wait-calls.patch
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0004-ALSA-control-Minor-optimization-for-SNDRV_CTL_IOCTL_.patch
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0005-ALSA-pcm-Block-the-release-until-the-system-resume-f.patch
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0006-ALSA-hda-Add-frozen-flag-for-prohibiting-hardware-ac.patch
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0007-ALSA-hda-Add-support-for-BARs-move-on-PCI-rescan.patch
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