3.4.106: futex: Wrong back port of 9e9aab5dbf?
Hello,
from a private -stable review we think that the commit 9e9aab5dbf ("futex: Ensure get_futex_key_refs() always implies a barrier" [1]) is not correctly back ported to 3.4.x:
The issue is that the memory barrier is introduced into drop_futex_key_refs() function instead of get_futex_key_refs() function.
Additionally, we are unsure if the futex commits this commit is fixing are really in < 3.4.106. I.e. we are unsure if this fix is needed at all. Or at least if some additional futex commits are needed.
Do you like to check?
Best regards
Dirk
Hi Dirk,
Quoted 10 lines · Dirk Behme
Hello,
from a private -stable review we think that the commit
9e9aab5dbf("futex: Ensureget_futex_key_refs()always implies a barrier" [1]) is not correctly back ported to 3.4.x:The issue is that the memory barrier is introduced into
drop_futex_key_refs()function instead ofget_futex_key_refs()function.Additionally, we are unsure if the futex commits this commit is fixing are really in < 3.4.106. I.e. we are unsure if this fix is needed at all. Or at least if some additional futex commits are needed.
Do you like to check?
I've confired this commit isn't needed for 3.4.y. It was backported quite long ago, and at that time I hadn't improved my scripts to check the Fixes tag. Fortunately seems this mistake won't cause serious issue.
I'll revert it in the coming 3.4.109. Thanks for the review!