linux-kernel - [PATCH 040/208] x86/fpu: Add kernel_fpu

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Date:	Tue,  5 May 2015 18:24:20 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	linux-kernel@...r.kernel.org
Cc:	Andy Lutomirski <luto@...capital.net>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Fenghua Yu <fenghua.yu@...el.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 040/208] x86/fpu: Add kernel_fpu_disabled()

Instead of open-coded in_kernel_fpu access, Use kernel_fpu_disabled() in
interrupted_kernel_fpu_idle(), matching the other kernel_fpu_*() methods.

Also add some documentation for in_kernel_fpu.

Reviewed-by: Borislav Petkov <bp@...en8.de>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Fenghua Yu <fenghua.yu@...el.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/fpu/core.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index bcf705751d02..87f10b49da47 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -7,6 +7,17 @@
  */
 #include <asm/fpu-internal.h>
 
+/*
+ * Track whether the kernel is using the FPU state
+ * currently.
+ *
+ * This flag is used:
+ *
+ *   - by IRQ context code to potentially use the FPU
+ *     if it's unused.
+ *
+ *   - to debug kernel_fpu_begin()/end() correctness
+ */
 static DEFINE_PER_CPU(bool, in_kernel_fpu);
 
 static void kernel_fpu_disable(void)
@@ -21,6 +32,11 @@ static void kernel_fpu_enable(void)
 	this_cpu_write(in_kernel_fpu, false);
 }
 
+static bool kernel_fpu_disabled(void)
+{
+	return this_cpu_read(in_kernel_fpu);
+}
+
 /*
  * Were we in an interrupt that interrupted kernel mode?
  *
@@ -35,7 +51,7 @@ static void kernel_fpu_enable(void)
  */
 static bool interrupted_kernel_fpu_idle(void)
 {
-	if (this_cpu_read(in_kernel_fpu))
+	if (kernel_fpu_disabled())
 		return false;
 
 	if (use_eager_fpu())
-- 
2.1.0

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