remove sched notifier for cross-cpu migrations
authorMarcelo Tosatti <mtosatti@redhat.com>
Thu, 11 Jul 2013 01:21:57 +0000 (22:21 -0300)
committerPaolo Bonzini <pbonzini@redhat.com>
Thu, 18 Jul 2013 10:29:30 +0000 (12:29 +0200)
commite04c5d76b0cfb66cadd900cf147526f2271884b8
treea303b66c1fc1ae7786148d2f50e8b0b86290162b
parentb3897a49e22fc173efa77527a447c714f753f681
remove sched notifier for cross-cpu migrations

Linux as a guest on KVM hypervisor, the only user of the pvclock
vsyscall interface, does not require notification on task migration
because:

1. cpu ID number maps 1:1 to per-CPU pvclock time info.
2. per-CPU pvclock time info is updated if the
   underlying CPU changes.
3. that version is increased whenever underlying CPU
   changes.

Which is sufficient to guarantee nanoseconds counter
is calculated properly.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
arch/x86/include/asm/pvclock.h
arch/x86/kernel/pvclock.c
arch/x86/vdso/vclock_gettime.c
include/linux/sched.h
kernel/sched/core.c