[PATCH 3/4] x86/fpu: use restore_init_xstate() instead of math_state_restore() on kthread exec

Oleg Nesterov
2015-03-11T17:37:00Z

Change flush_thread() to do user_fpu_begin() + restore_init_xstate()
and avoid math_state_restore().

Note: "TODO: cleanup this horror" is still valid. We do not need
init_fpu() at all, we only need fpu_alloc() + memset(0). But this needs
other changes, in particular user_fpu_begin() should set used_math().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
arch/x86/kernel/process.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index dd9a069..c396de2 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -142,7 +142,8 @@ void flush_thread(void)
/* kthread execs. TODO: cleanup this horror. */
if (WARN_ON(init_fpu(current)))
force_sig(SIGKILL, current);
- math_state_restore();
+ user_fpu_begin();
+ restore_init_xstate();
}
}

--
1.5.5.1