linux-kernel - [PATCH 4/4] x86/fpu: don't abuse drop_init_fpu() in flush

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Message-ID: <20150311173507.GF5032@redhat.com>
Date:	Wed, 11 Mar 2015 18:35:07 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Dave Hansen <dave.hansen@...el.com>, Borislav Petkov <bp@...e.de>,
	Ingo Molnar <mingo@...nel.org>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Pekka Riikonen <priikone@....fi>,
	Rik van Riel <riel@...hat.com>,
	Suresh Siddha <sbsiddha@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"Yu, Fenghua" <fenghua.yu@...el.com>,
	Quentin Casasnovas <quentin.casasnovas@...cle.com>
Subject: [PATCH 4/4] x86/fpu: don't abuse drop_init_fpu() in flush_thread()

drop_init_fpu() makes no sense. We need drop_fpu() and only if
!use_eager_fpu().

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 arch/x86/kernel/process.c |   11 ++++-------
 1 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index c396de2..2e71120 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -131,14 +131,11 @@ void flush_thread(void)
 	flush_ptrace_hw_breakpoint(tsk);
 	memset(tsk->thread.tls_array, 0, sizeof(tsk->thread.tls_array));
 
-	drop_init_fpu(tsk);
-	/*
-	 * Free the FPU state for non xsave platforms. They get reallocated
-	 * lazily at the first use.
-	 */
-	if (!use_eager_fpu())
+	if (!use_eager_fpu()) {
+		/* FPU state will be reallocated lazily at the first use. */
+		drop_fpu(tsk);
 		free_thread_xstate(tsk);
-	else if (!used_math()) {
+	} else if (!used_math()) {
 		/* kthread execs. TODO: cleanup this horror. */
 		if (WARN_ON(init_fpu(current)))
 			force_sig(SIGKILL, current);
-- 
1.5.5.1


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