Re: [linus:master] [atomic] 80047d84ee: WARNING:at_include/linux/instrumented.h:#__split_huge_pmd_locked

[Finn Thain]

On Tue, 3 Nov 2026, kernel test robot wrote:

> 
> kernel test robot noticed "WARNING:at_include/linux/instrumented.h:#__split_huge_pmd_locked" on:
> 
> commit: 80047d84eed25e9c92cfb9169980a0dfec110246 ("atomic: add alignment check to instrumented atomic operations") https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
> 

It appears that a misaligned lock was accessed in 
__split_huge_pmd_locked() back in 6.19.0-rc on i386.

And it appears that bisection landed on commit 80047d84eed2 ("atomic: add 
alignment check to instrumented atomic operations") because that's when 
the check got added to detect such accesses.

If the misaligned atomic operation is somehow normal in this situation (?) 
then I guess it's a false positive from DEBUG_ATOMIC=y.

But if it was unintentional, the next step would probably be to check 
whether the current mainline kernel has the same issue.

I have to confess to a state of ignorance about the mm subsystem so I 
don't know what to conclude here.