** Changed in: linux (Ubuntu Yakkety)
Status: In Progress => Fix Committed
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https://bugs.launchpad.net/bugs/1669023
Title:
Kernel: Fix Transactional memory config typo
Status in linux package in Ubuntu:
Fix Released
Status in linux source package in Yakkety:
Fix Committed
Status in linux source package in Zesty:
Fix Released
Bug description:
Canonical,
Please include the following fix on 16.10. This typo is causing some issue
on TM.
The patches that causes this problem is
ec2a04841b785373a6379af66032201a2b90922b on yakkety-ubuntu repo.
commit 39715bf972ed4fee18fe5409609a971fb16b1771
Author: Valentin Rothberg <[email protected]>
Date: Wed Oct 5 07:57:26 2016 +0200
powerpc/process: Fix CONFIG_ALIVEC typo in restore_tm_state()
It should be ALTIVEC, not ALIVEC.
Cyril explains: If a thread performs a transaction with altivec and then
gets preempted for whatever reason, this bug may cause the kernel to not
re-enable altivec when that thread runs again. This will result in an
altivec unavailable fault, when that fault happens inside a user
transaction the kernel has no choice but to enable altivec and doom the
transaction.
The result is that transactions using altivec may get aborted more often
than they should.
The difficulty in catching this with a selftest is my deliberate use of
the word may above. Optimisations to avoid FPU/altivec/VSX faults mean
that the kernel will always leave them on for 255 switches. This code
prevents the kernel turning it off if it got to the 256th switch (and
userspace was transactional).
Fixes: dc16b553c949 ("powerpc: Always restore FPU/VEC/VSX if hardware
transactional memory in use")
Reviewed-by: Cyril Bur <[email protected]>
Signed-off-by: Valentin Rothberg <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
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