Messages in this thread | | | Date | Mon, 27 Apr 2015 17:19:46 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH v2] x86/fpu: always restore_xinit_state() when use_eager_cpu() |
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Thanks!
On 04/27, Bobby Powers wrote: > > v2: switch used_math() -> tsk_used_math(tsk) to consistently use the > grabbed tsk instead of current, like in the rest of flush_thread(). > > Oleg's commit f893959b ("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 f893959b 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. > > Fixes: f893959b ("x86/fpu: Don't abuse drop_init_fpu() in flush_thread()") > Signed-off-by: Bobby Powers <bobbypowers@gmail.com> > Acked-by: Oleg Nesterov <oleg@redhat.com> > Cc: Andi Kleen <ak@linux.intel.com> > Cc: Borislav Petkov <bp@suse.de> > Cc: Ingo Molnar <mingo@kernel.org> > Cc: Andy Lutomirski <luto@amacapital.net> > Cc: Dave Hansen <dave.hansen@intel.com> > Cc: Fenghua Yu <fenghua.yu@intel.com> > Cc: Linus Torvalds <torvalds@linux-foundation.org> > Cc: Pekka Riikonen <priikone@iki.fi> > Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com> > Cc: Rik van Riel <riel@redhat.com> > Cc: Suresh Siddha <sbsiddha@gmail.com> > --- > 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 8213da6..1a6fcf8 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(); > } > } > -- > 2.3.6 >
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