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| author | Oleg Nesterov <oleg@redhat.com> | 2015-03-13 18:30:30 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-03-23 10:13:58 +0100 |
| commit | f893959b0898bd876673adbeb6798bdf25c034d7 (patch) | |
| tree | c0b9d2b3d247912f35e0f1304767e65975205842 /arch/x86/kernel/process.c | |
| parent | 9cb6ce823bbd1adbe15e30bd1435c84c2e271767 (diff) | |
| download | linux-stable-f893959b0898bd876673adbeb6798bdf25c034d7.tar.gz linux-stable-f893959b0898bd876673adbeb6798bdf25c034d7.tar.bz2 linux-stable-f893959b0898bd876673adbeb6798bdf25c034d7.zip | |
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: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Borislav 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.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/kernel/process.c')
| -rw-r--r-- | arch/x86/kernel/process.c | 15 |
1 files changed, 6 insertions, 9 deletions
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 6b058296a456..1d2ebadba7ac 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -132,17 +132,14 @@ void flush_thread(void) flush_ptrace_hw_breakpoint(tsk); memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array)); - drop_init_fpu(tsk); - /* - * Free the FPU state for non xsave platforms. They get reallocated - * lazily at the first use. - */ - if (!use_eager_fpu()) + if (!use_eager_fpu()) { + /* FPU state will be reallocated lazily at the first use. */ + drop_fpu(tsk); free_thread_xstate(tsk); - else if (!used_math()) { + } else if (!used_math()) { /* kthread execs. TODO: cleanup this horror. */ - if (WARN_ON(init_fpu(current))) - force_sig(SIGKILL, current); + if (WARN_ON(init_fpu(tsk))) + force_sig(SIGKILL, tsk); user_fpu_begin(); restore_init_xstate(); } |