Commit 089f9fba authored by Oleg Nesterov's avatar Oleg Nesterov Committed by H. Peter Anvin

i387: ptrace breaks the lazy-fpu-restore logic

Starting from 7e16838d "i387: support lazy restore of FPU state"
we assume that fpu_owner_task doesn't need restore_fpu_checking()
on the context switch, its FPU state should match what we already
have in the FPU on this CPU.

However, debugger can change the tracee's FPU state, in this case
we should reset fpu.last_cpu to ensure fpu_lazy_restore() can't
return true.

Change init_fpu() to do this, it is called by user_regset->set()
methods.
Reported-by: default avatarJan Kratochvil <jan.kratochvil@redhat.com>
Suggested-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Link: http://lkml.kernel.org/r/20120416204815.GB24884@redhat.com
Cc: <stable@vger.kernel.org> v3.3
Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent 68894632
......@@ -235,6 +235,7 @@ int init_fpu(struct task_struct *tsk)
if (tsk_used_math(tsk)) {
if (HAVE_HWFP && tsk == current)
unlazy_fpu(tsk);
tsk->thread.fpu.last_cpu = ~0;
return 0;
}
......
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