diff options
| author | Oleg Nesterov <oleg@redhat.com> | 2015-01-19 19:51:32 +0100 |
|---|---|---|
| committer | Borislav Petkov <bp@suse.de> | 2015-02-23 15:50:28 +0100 |
| commit | 7aeccb83e76316b365e4b44a1dd982ee22a7d8b2 (patch) | |
| tree | 9d17e8a0f9c68f33d36154da30e014c489a9f478 /arch/x86/kernel/i387.c | |
| parent | f353e612304ba752d6b613dc02eae8116cd3e27b (diff) | |
x86/fpu: __kernel_fpu_begin() should clear fpu_owner_task even if use_eager_fpu()
__kernel_fpu_begin() does nothing if !__thread_has_fpu() && use_eager_fpu(),
perhaps it assumes that this case is simply impossible. This is certainly
not possible if in_interrupt() == T; interrupted_user_mode() should have
FPU, and interrupted_kernel_fpu_idle() should fail if !__thread_has_fpu().
However, even if use_eager_fpu() == T a task can do drop_fpu(), then switch
to another thread which becomes fpu_owner_task, then resume and call some
function which does kernel_fpu_begin(). Say, an exiting task does a lot of
things after exit_thread(), it is not safe to assume that it can't use FPU
in these paths.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Suresh Siddha <sbsiddha@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Pekka Riikonen <priikone@iki.fi>
Link: http://lkml.kernel.org/r/20150119185132.GB16427@redhat.com
Signed-off-by: Borislav Petkov <bp@suse.de>
Diffstat (limited to 'arch/x86/kernel/i387.c')
| -rw-r--r-- | arch/x86/kernel/i387.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c index f59d80622e60..ad3a2a23f248 100644 --- a/arch/x86/kernel/i387.c +++ b/arch/x86/kernel/i387.c @@ -93,9 +93,10 @@ void __kernel_fpu_begin(void) if (__thread_has_fpu(me)) { __save_init_fpu(me); - } else if (!use_eager_fpu()) { + } else { this_cpu_write(fpu_owner_task, NULL); - clts(); + if (!use_eager_fpu()) + clts(); } } EXPORT_SYMBOL(__kernel_fpu_begin); |