Messages in this thread Patch in this message | | | From | Bobby Powers <> | Subject | [PATCH v2] x86/fpu: always restore_xinit_state() when use_eager_cpu() | Date | Mon, 27 Apr 2015 08:10:41 -0700 |
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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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