From c88d47480d300eaad80c213d50c9bf6077fc49bc Mon Sep 17 00:00:00 2001 From: Bobby Powers Date: Mon, 27 Apr 2015 08:10:41 -0700 Subject: [PATCH] x86/fpu: Always restore_xinit_state() when use_eager_cpu() The following commit: f893959b0898 ("x86/fpu: Don't abuse drop_init_fpu() in flush_thread()") removed drop_init_fpu() usage from flush_thread(). This seems to break things for me - the Go 1.4 test suite fails all over the place with floating point comparision errors (offending commit found through bisection). The functional change was that flush_thread() after this commit only calls restore_init_xstate() when both use_eager_fpu() and !used_math() are true. drop_init_fpu() (now fpu_reset_state()) calls restore_init_xstate() regardless of whether current used_math() - apply the same logic here. Switch used_math() -> tsk_used_math(tsk) to consistently use the grabbed tsk instead of current, like in the rest of flush_thread(). Tested-by: Dave Hansen Signed-off-by: Bobby Powers Signed-off-by: Borislav Petkov Acked-by: Oleg Nesterov Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Fenghua Yu Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Pekka Riikonen Cc: Quentin Casasnovas Cc: Rik van Riel Cc: Suresh Siddha Cc: Thomas Gleixner Fixes: f893959b ("x86/fpu: Don't abuse drop_init_fpu() in flush_thread()") Link: http://lkml.kernel.org/r/1430147441-9820-1-git-send-email-bobbypowers@gmail.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/process.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index bfc99b3b6522..6e338e3b1dc0 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -156,11 +156,13 @@ void flush_thread(void) /* FPU state will be reallocated lazily at the first use. */ drop_fpu(tsk); free_thread_xstate(tsk); - } else if (!used_math()) { - /* kthread execs. TODO: cleanup this horror. */ - if (WARN_ON(init_fpu(tsk))) - force_sig(SIGKILL, tsk); - user_fpu_begin(); + } else { + if (!tsk_used_math(tsk)) { + /* kthread execs. TODO: cleanup this horror. */ + if (WARN_ON(init_fpu(tsk))) + force_sig(SIGKILL, tsk); + user_fpu_begin(); + } restore_init_xstate(); } }