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Re: kern/55512: sdmmc locking broken

The following reply was made to PR kern/55512; it has been noted by GNATS.

From: (Michael van Elst)
Subject: Re: kern/55512: sdmmc locking broken
Date: Wed, 22 Jul 2020 15:19:18 -0000 (UTC) (Martin Husemann) writes:
 > That would be fine, but still the locking seems to be broken. I'm
 > pretty sure I saw concurrent cmds issued by different CPUs while trying
 > to debug my eMMC issue (the strange timings you noticed in my debug
 > lock on tech-kern) on Odroid C2.
 Actually I noticed that the driver returned a timeout while almost
 no time had passed, definitely not qualifying for a timeout.
 kprintf uses getnanouptime(), I'm not sure if readouts on
 different CPUs are guaranteed to be monotonic.
                                 Michael van Elst
                                 "A potential Snark may lurk in every tree."

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