linux-kernel - [PATCH 1/8] x86, fpu: unlazy_fpu: don't reset thread.fpu

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Message-Id: <1423252925-14451-2-git-send-email-riel@redhat.com>
Date:	Fri,  6 Feb 2015 15:01:58 -0500
From:	riel@...hat.com
To:	oleg@...hat.com
Cc:	dave.hansen@...ux.intel.com, sbsiddha@...il.com,
	luto@...capital.net, tglx@...utronix.de, mingo@...nel.org,
	hpa@...or.com, fenghua.yu@...el.com, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/8] x86, fpu: unlazy_fpu: don't reset thread.fpu_counter

From: Oleg Nesterov <oleg@...hat.com>

It is not clear why the "else" branch clears ->fpu_counter, this makes
no sense.

If use_eager_fpu() then this has no effect. Otherwise, if we actually
wanted to prevent fpu preload after the context switch we would need to
reset it unconditionally, even if __thread_has_fpu().

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Signed-off-by: Rik van Riel <riel@...hat.com>
---
 arch/x86/kernel/i387.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index 47348653503a..c3b92c0975cd 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -122,8 +122,7 @@ void unlazy_fpu(struct task_struct *tsk)
 	if (__thread_has_fpu(tsk)) {
 		__save_init_fpu(tsk);
 		__thread_fpu_end(tsk);
-	} else
-		tsk->thread.fpu_counter = 0;
+	}
 	preempt_enable();
 }
 EXPORT_SYMBOL(unlazy_fpu);
-- 
1.9.3

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