linux-kernel - [PATCH 2/2] x86, xsave: remove thread_has_fpu() bug check in __sanitize_i387

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Date:	Mon,  7 May 2012 12:07:21 -0700
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	torvalds@...ux-foundation.org, hpa@...or.com, mingo@...e.hu,
	oleg@...hat.com
Cc:	suresh@...stanetworks.com, linux-kernel@...r.kernel.org,
	Suresh Siddha <suresh.b.siddha@...el.com>
Subject: [PATCH 2/2] x86, xsave: remove thread_has_fpu() bug check in __sanitize_i387_state()

Code paths like fork(), exit() and signal handling flush the fpu
state explicitly to the structures in memory.

BUG_ON() in __sanitize_i387_state() is checking that the fpu state
is not live any more. But for preempt kernels, task can be scheduled
out and in at any place and the preload_fpu logic during context switch
can make the fpu registers live again.

Similarly during core dump, thread dumping the core can schedule out
and in for page-allocations etc in non-preempt case.

So remove the paranoid check, even though it caught a bug in the
multi-threaded core dump case (fixed in the previous patch).

Signed-off-by: Suresh Siddha <suresh.b.siddha@...el.com>
---
 arch/x86/kernel/xsave.c |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index e62728e..bd18149 100644
--- a/arch/x86/kernel/xsave.c
+++ b/arch/x86/kernel/xsave.c
@@ -48,8 +48,6 @@ void __sanitize_i387_state(struct task_struct *tsk)
 	if (!fx)
 		return;

-	BUG_ON(__thread_has_fpu(tsk));
-
 	xstate_bv = tsk->thread.fpu.state->xsave.xsave_hdr.xstate_bv;

 	/*
-- 
1.7.6.5

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