Commit-ID: e6e9cac8c3417b43498b243c1f8f11780e157168
Gitweb: http://git.kernel.org/tip/e6e9cac8c3417b43498b243c1f8f11780e157168
Author: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
AuthorDate: Fri, 24 Apr 2009 00:40:59 -0700
Committer: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
CommitDate: Wed, 17 Jun 2009 13:21:25 -0700
x86: split out core __math_state_restore
Split the core fpu state restoration out into __math_state_restore, which
assumes that cr0.TS is clear and that the fpu context has been initialized.
This will be used during context switch. There are two reasons this is
desireable:
- There's a small clarification. When __switch_to() calls math_state_restore,
it relies on the fact that tsk_used_math() returns true, and so will
never do a blocking init_fpu(). __math_state_restore() does not have
(or need) that logic, so the question never arises.
- It allows the clts() to be moved earler in __switch_to() so it can be performed
while cpu context updates are batched (will be done in a later patch).
[ Impact: refactor code to make reuse cleaner; no functional change ]
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
Cc: Alok Kataria <akataria@xxxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
---
arch/x86/include/asm/i387.h | 1 +
arch/x86/kernel/traps.c | 33 +++++++++++++++++++++++----------
2 files changed, 24 insertions(+), 10 deletions(-)
diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h
index 175adf5..2e75292 100644
--- a/arch/x86/include/asm/i387.h
+++ b/arch/x86/include/asm/i387.h
@@ -26,6 +26,7 @@ extern void fpu_init(void);
extern void mxcsr_feature_mask_init(void);
extern int init_fpu(struct task_struct *child);
extern asmlinkage void math_state_restore(void);
+extern void __math_state_restore(void);
extern void init_thread_xstate(void);
extern int dump_fpu(struct pt_regs *, struct user_i387_struct *);
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 5f935f0..71b9166 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -814,6 +814,28 @@ asmlinkage void __attribute__((weak)) smp_threshold_interrupt(void)
}
/*
+ * __math_state_restore assumes that cr0.TS is already clear and the
+ * fpu state is all ready for use. Used during context switch.
+ */
+void __math_state_restore(void)
+{
+ struct thread_info *thread = current_thread_info();
+ struct task_struct *tsk = thread->task;
+
+ /*
+ * Paranoid restore. send a SIGSEGV if we fail to restore the state.
+ */
+ if (unlikely(restore_fpu_checking(tsk))) {
+ stts();
+ force_sig(SIGSEGV, tsk);
+ return;
+ }
+
+ thread->status |= TS_USEDFPU; /* So we fnsave on switch_to() */
+ tsk->fpu_counter++;
+}
+
+/*
* 'math_state_restore()' saves the current math information in the
* old math state array, and gets the new ones from the current task
*
@@ -844,17 +866,8 @@ asmlinkage void math_state_restore(void)
}
clts(); /* Allow maths ops (or we recurse) */
- /*
- * Paranoid restore. send a SIGSEGV if we fail to restore the state.
- */
- if (unlikely(restore_fpu_checking(tsk))) {
- stts();
- force_sig(SIGSEGV, tsk);
- return;
- }
- thread->status |= TS_USEDFPU; /* So we fnsave on switch_to() */
- tsk->fpu_counter++;
+ __math_state_restore();
}
EXPORT_SYMBOL_GPL(math_state_restore);
--
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