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 <[email protected]>
Acked-by: Oleg Nesterov <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Fenghua Yu <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Pekka Riikonen <[email protected]>
Cc: Quentin Casasnovas <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Suresh Siddha <[email protected]>
---
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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