Commit f893959b authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Ingo Molnar

x86/fpu: Don't abuse drop_init_fpu() in flush_thread()

flush_thread() -> drop_init_fpu() is suboptimal and confusing. It does
drop_fpu() or restore_init_xstate() depending on !use_eager_fpu(). But
flush_thread() too checks eagerfpu right after that, and if it is true
then restore_init_xstate() just burns CPU for no reason. We are going to
load init_xstate_buf again after we set used_math()/user_has_fpu(), until
then the FPU state can't survive after switch_to().

Remove it, and change the "if (!use_eager_fpu())" to call drop_fpu().
While at it, clean up the tsk/current usage.
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
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>
Link: http://lkml.kernel.org/r/20150313173030.GA31217@redhat.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 9cb6ce82
...@@ -132,17 +132,14 @@ void flush_thread(void) ...@@ -132,17 +132,14 @@ void flush_thread(void)
flush_ptrace_hw_breakpoint(tsk); flush_ptrace_hw_breakpoint(tsk);
memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array)); memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));
drop_init_fpu(tsk); if (!use_eager_fpu()) {
/* /* FPU state will be reallocated lazily at the first use. */
* Free the FPU state for non xsave platforms. They get reallocated drop_fpu(tsk);
* lazily at the first use.
*/
if (!use_eager_fpu())
free_thread_xstate(tsk); free_thread_xstate(tsk);
else if (!used_math()) { } else if (!used_math()) {
/* kthread execs. TODO: cleanup this horror. */ /* kthread execs. TODO: cleanup this horror. */
if (WARN_ON(init_fpu(current))) if (WARN_ON(init_fpu(tsk)))
force_sig(SIGKILL, current); force_sig(SIGKILL, tsk);
user_fpu_begin(); user_fpu_begin();
restore_init_xstate(); restore_init_xstate();
} }
......
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