diff options
author | Oleg Nesterov <oleg@redhat.com> | 2015-02-06 15:01:59 -0500 |
---|---|---|
committer | Borislav Petkov <bp@suse.de> | 2015-02-19 11:12:46 +0100 |
commit | 1a2a7f4ec8e3a7ac582dac4d01fcc7e8acd3bb30 (patch) | |
tree | e02cb93cfeca07de18639d4a1ee71cd7a207d294 /arch/x86/kernel | |
parent | a9241ea5fd709fc935dade130f4e3b2612bbe9e3 (diff) |
x86/fpu: Don't do __thread_fpu_end() if use_eager_fpu()
unlazy_fpu()->__thread_fpu_end() doesn't look right if use_eager_fpu().
Unconditional __thread_fpu_end() is only correct if we know that this
thread can't return to user-mode and use FPU.
Fortunately it has only 2 callers. fpu_copy() checks use_eager_fpu(),
and init_fpu(current) can be only called by the coredumping thread via
regset->get(). But it is exported to modules, and imo this should be
fixed anyway.
And if we check use_eager_fpu() we can use __save_fpu() like fpu_copy()
and save_init_fpu() do.
- It seems that even !use_eager_fpu() case doesn't need the unconditional
__thread_fpu_end(), we only need it if __save_init_fpu() returns 0.
- It is still not clear to me if __save_init_fpu() can safely nest with
another save + restore from __kernel_fpu_begin(). If not, we can use
kernel_fpu_disable() to fix the race.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1423252925-14451-3-git-send-email-riel@redhat.com
Signed-off-by: Borislav Petkov <bp@suse.de>
Diffstat (limited to 'arch/x86/kernel')
-rw-r--r-- | arch/x86/kernel/i387.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c index 4d0db9ed58e0..f3ced6f4b2b6 100644 --- a/arch/x86/kernel/i387.c +++ b/arch/x86/kernel/i387.c @@ -106,8 +106,12 @@ void unlazy_fpu(struct task_struct *tsk) { preempt_disable(); if (__thread_has_fpu(tsk)) { - __save_init_fpu(tsk); - __thread_fpu_end(tsk); + if (use_eager_fpu()) { + __save_fpu(tsk); + } else { + __save_init_fpu(tsk); + __thread_fpu_end(tsk); + } } preempt_enable(); } |