diff options
| author | Heiko Carstens | 2019-11-18 09:38:37 +0100 |
|---|---|---|
| committer | Vasily Gorbik | 2019-11-30 10:52:44 +0100 |
| commit | 5a5525b0488ce31e19065f8527dbf50266b5b712 (patch) | |
| tree | 962f0b570a299c36ea29f9dd2cb14943b488ca68 /arch/s390/include | |
| parent | a2308c11ecbc3471ebb7435ee8075815b1502ef0 (diff) | |
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>
Diffstat (limited to 'arch/s390/include')
| -rw-r--r-- | arch/s390/include/asm/vdso.h | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/arch/s390/include/asm/vdso.h b/arch/s390/include/asm/vdso.h index 169d7604eb80..3bcfdeb01395 100644 --- a/arch/s390/include/asm/vdso.h +++ b/arch/s390/include/asm/vdso.h @@ -41,8 +41,17 @@ struct vdso_data { struct vdso_per_cpu_data { __u64 ectg_timer_base; __u64 ectg_user_time; - __u32 cpu_nr; - __u32 node_id; + /* + * Note: node_id and cpu_nr must be at adjacent memory locations. + * VDSO userspace must read both values with a single instruction. + */ + union { + __u64 getcpu_val; + struct { + __u32 node_id; + __u32 cpu_nr; + }; + }; }; extern struct vdso_data *vdso_data; |