linux-kernel - [PATCH 2/6] x86, fpu: remove unnecessary user_fpu_end() in save_xstate

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Message-Id: <1345842782-24175-3-git-send-email-suresh.b.siddha@intel.com>
Date:	Fri, 24 Aug 2012 14:12:58 -0700
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	hpa@...or.com, mingo@...nel.org, torvalds@...ux-foundation.org,
	andreas.herrmann3@....com, bp@...64.org, robert.richter@....com
Cc:	linux-kernel@...r.kernel.org,
	Suresh Siddha <suresh.b.siddha@...el.com>
Subject: [PATCH 2/6] x86, fpu: remove unnecessary user_fpu_end() in save_xstate_sig()

Few lines below we do drop_fpu() which is more safer. Remove the
unnecessary user_fpu_end() in save_xstate_sig(), which allows
the drop_fpu() to ignore any pending exceptions from the user-space
and drop the current fpu.

Signed-off-by: Suresh Siddha <suresh.b.siddha@...el.com>
---
 arch/x86/include/asm/fpu-internal.h |   17 +++--------------
 arch/x86/kernel/xsave.c             |    1 -
 2 files changed, 3 insertions(+), 15 deletions(-)

diff --git a/arch/x86/include/asm/fpu-internal.h b/arch/x86/include/asm/fpu-internal.h
index fe95ad0..fac39e9 100644
--- a/arch/x86/include/asm/fpu-internal.h
+++ b/arch/x86/include/asm/fpu-internal.h
@@ -412,22 +412,11 @@ static inline void __drop_fpu(struct task_struct *tsk)
 }
 
 /*
- * The actual user_fpu_begin/end() functions
- * need to be preemption-safe.
+ * Need to be preemption-safe.
  *
- * NOTE! user_fpu_end() must be used only after you
- * have saved the FP state, and user_fpu_begin() must
- * be used only immediately before restoring it.
- * These functions do not do any save/restore on
- * their own.
+ * NOTE! user_fpu_begin() must be used only immediately before restoring
+ * it. This function does not do any save/restore on their own.
  */
-static inline void user_fpu_end(void)
-{
-	preempt_disable();
-	__thread_fpu_end(current);
-	preempt_enable();
-}
-
 static inline void user_fpu_begin(void)
 {
 	preempt_disable();
diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index 6cfc7d9..f0bb844 100644
--- a/arch/x86/kernel/xsave.c
+++ b/arch/x86/kernel/xsave.c
@@ -254,7 +254,6 @@ int save_xstate_sig(void __user *buf, void __user *buf_fx, int size)
 		/* Update the thread's fxstate to save the fsave header. */
 		if (ia32_fxstate)
 			fpu_fxsave(&tsk->thread.fpu);
-		user_fpu_end();
 	} else {
 		sanitize_i387_state(tsk);
 		if (__copy_to_user(buf_fx, xsave, xstate_size))
-- 
1.7.6.5

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