s390/vdso: fix getcpu

getcpu reads the required values for cpu and node with two
instructions. This might lead to an inconsistent result if user space
gets preempted and migrated to a different CPU between the two
instructions.

Fix this by using just a single instruction to read both values at
once.

This is currently rather a theoretical bug, since there is no real
NUMA support available (except for NUMA emulation).

Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Heiko Carstens 2019-11-18 09:38:37 +01:00 • committed by Vasily Gorbik
commit 5a5525b048
4 changed files with 14 additions and 10 deletions