lkml.org 
[lkml]   [2010]   [Sep]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[tip:x86/fpu] x86-64, fpu: Disable preemption when using TS_USEDFPU
Commit-ID:  a4d4fbc7735bba6654b20f859135f9d3f8fe7f76
Gitweb: http://git.kernel.org/tip/a4d4fbc7735bba6654b20f859135f9d3f8fe7f76
Author: Brian Gerst <brgerst@gmail.com>
AuthorDate: Fri, 3 Sep 2010 21:17:12 -0400
Committer: H. Peter Anvin <hpa@linux.intel.com>
CommitDate: Thu, 9 Sep 2010 14:16:45 -0700

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>
---
arch/x86/include/asm/i387.h | 15 ---------------
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 88065e3..8b40a83 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 3d9ea53..b3d7a3a 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)

\
 
 \ /
  Last update: 2010-09-10 03:57    [W:0.213 / U:0.112 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site