diff options
| author | Brian Gerst <brgerst@gmail.com> | 2010-09-03 21:17:12 -0400 |
|---|---|---|
| committer | H. Peter Anvin <hpa@linux.intel.com> | 2010-09-09 14:16:45 -0700 |
| commit | a4d4fbc7735bba6654b20f859135f9d3f8fe7f76 (patch) | |
| tree | 4b501fbfbce08e3222f137a284b354425162f873 /arch/x86 | |
| parent | bfd946cb891800d408decaae268a3480775178a3 (diff) | |
x86-64, fpu: Disable preemption when using TS_USEDFPU
Consolidates code and fixes the below race for 64-bit.
commit 9fa2f37bfeb798728241cc4a19578ce6e4258f25
Author: torvalds <torvalds>
Date: Tue Sep 2 07:37:25 2003 +0000
Be a lot more careful about TS_USEDFPU and preemption
We had some races where we testecd (or set) TS_USEDFPU together
with sequences that depended on the setting (like clearing or
setting the TS flag in %cr0) and we could be preempted in between,
which screws up the FPU state, since preemption will itself change
USEDFPU and the TS flag.
This makes it a lot more explicit: the "internal" low-level FPU
functions ("__xxxx_fpu()") all require preemption to be disabled,
and the exported "real" functions will make sure that is the case.
One case - in __switch_to() - was switched to the non-preempt-safe
internal version, since the scheduler itself has already disabled
preemption.
BKrev: 3f5448b5WRiQuyzAlbajs3qoQjSobw
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Acked-by: Pekka Enberg <penberg@kernel.org>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
LKML-Reference: <1283563039-3466-6-git-send-email-brgerst@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/include/asm/i387.h | 15 | ||||
| -rw-r--r-- | arch/x86/kernel/process_64.c | 2 |
2 files changed, 1 insertions, 16 deletions
diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h index 88065e3a03c0..8b40a8379cc2 100644 --- a/arch/x86/include/asm/i387.h +++ b/arch/x86/include/asm/i387.h @@ -387,19 +387,6 @@ static inline void irq_ts_restore(int TS_state) stts(); } -#ifdef CONFIG_X86_64 - -static inline void save_init_fpu(struct task_struct *tsk) -{ - __save_init_fpu(tsk); - stts(); -} - -#define unlazy_fpu __unlazy_fpu -#define clear_fpu __clear_fpu - -#else /* CONFIG_X86_32 */ - /* * These disable preemption on their own and are safe */ @@ -425,8 +412,6 @@ static inline void clear_fpu(struct task_struct *tsk) preempt_enable(); } -#endif /* CONFIG_X86_64 */ - /* * i387 state interaction */ diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 3d9ea531ddd1..b3d7a3a04f38 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -424,7 +424,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) load_TLS(next, cpu); /* Must be after DS reload */ - unlazy_fpu(prev_p); + __unlazy_fpu(prev_p); /* Make sure cpu is ready for new context */ if (preload_fpu) |