linux-kernel - [PATCH 4/5] x86, fpu: shift init_fpu() from eager_fpu_init() to eager_fpu_init

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Message-ID: <20140824194743.GA27451@redhat.com>
Date:	Sun, 24 Aug 2014 21:47:43 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Al Viro <viro@...IV.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Fenghua Yu <fenghua.yu@...el.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Suresh Siddha <suresh.b.siddha@...el.com>
Cc:	Bean Anderson <bean@...lsystems.com>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 4/5] x86, fpu: shift init_fpu() from eager_fpu_init() to
	eager_fpu_init_bp()

This is not strictly needed, eager_fpu_init() is called before
the very first schedule() on this CPU, but let's remove the last
unconditional clear_used_math().

eager_fpu_init() does init_fpu() every time, but this is only needed
on boot CPU, otherwise this idle thread already has a valid fpu state
copied by arch_dup_task_struct().

And this allows to remove clear_used_math(). swapper/0 doesn't have
this flag when start_kernel() calls us, other idle threads correctly
have this flag set.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 arch/x86/kernel/xsave.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index 51be404..33f4ebe 100644
--- a/arch/x86/kernel/xsave.c
+++ b/arch/x86/kernel/xsave.c
@@ -601,19 +601,20 @@ void xsave_init(void)
 	this_func();
 }
 
-static inline void __init eager_fpu_init_bp(void)
+static void __init eager_fpu_init_bp(void)
 {
 	current->thread.fpu.state =
 	    alloc_bootmem_align(xstate_size, __alignof__(struct xsave_struct));
 	if (!init_xstate_buf)
 		setup_init_fpu_buf();
+
+	init_fpu(current);
 }
 
 void eager_fpu_init(void)
 {
 	static __refdata void (*boot_func)(void) = eager_fpu_init_bp;
 
-	clear_used_math();
 	current_thread_info()->status = 0;
 
 	if (eagerfpu == ENABLE)
@@ -633,7 +634,6 @@ void eager_fpu_init(void)
 	 * This is same as math_state_restore(). But use_xsave() is
 	 * not yet patched to use math_state_restore().
 	 */
-	init_fpu(current);
 	__thread_fpu_begin(current);
 	if (cpu_has_xsave)
 		xrstor_state(init_xstate_buf, -1);
-- 
1.5.5.1

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