Messages in this thread |  | | From | Linus Torvalds <> | Date | Fri, 27 Nov 2020 14:56:35 -0800 | Subject | Re: [GIT PULL] ARM: SoC fixes for v5.10, part 3 |
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On Fri, Nov 27, 2020 at 12:51 PM Arnd Bergmann <arnd@kernel.org> wrote: > > - Some DT patches for the Rockchip RK3399 platform, > in particular fixing the MMC device ordering that > recently became nondeterministic with async probe.
Uhhuh.
I didn't realize this MMC breakage happened.
That's just an MMC bug. Other subsystems have been able to do async probing without making device ordering be random.
So this really smells wrong, and I just never realized.
Added Douglas Anderson to the cc - the whole PROBE_PREFER_ASYNCHRONOUS behavior appears broken.
You basically should do the device numbering synchronously (or better yet - asynchronously, but single-threaded for the subsystem), and then asynchronously probe the actual device details after you've numbered them reliably.
This is not something new - we do this for pretty much all the other block devices, and MMC is just doing things wrong.
See SCSI probing for the traditional horrible cases (where just spinning up a disk could take tens of seconds). "Slow probing" is not an excuse of "random ordering".
Behaving randomly is simply not acceptable.
Linus
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