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From: Suresh Siddha <suresh.b.siddha@intel.com>
To: torvalds@linux-foundation.org, hpa@zytor.com, mingo@elte.hu,
	oleg@redhat.com
Cc: suresh@aristanetworks.com, linux-kernel@vger.kernel.org,
	Suresh Siddha <suresh.b.siddha@intel.com>
Subject: [PATCH 2/2] x86, xsave: remove thread_has_fpu() bug check in __sanitize_i387_state()
Date: Mon,  7 May 2012 12:07:21 -0700	[thread overview]
Message-ID: <1336417641-29771-2-git-send-email-suresh.b.siddha@intel.com> (raw)
In-Reply-To: <1336417641-29771-1-git-send-email-suresh.b.siddha@intel.com>

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@intel.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


  reply	other threads:[~2012-05-07 19:05 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-05-07 19:07 [PATCH 1/2] coredump: flush the fpu exit state for proper multi-threaded core dump Suresh Siddha
2012-05-07 19:07 ` Suresh Siddha [this message]
2012-05-07 19:15 ` Linus Torvalds
2012-05-07 20:09   ` Suresh Siddha
2012-05-08 23:18     ` Suresh Siddha
2012-05-08 23:18       ` [PATCH 1/3] " Suresh Siddha
2012-05-09 21:05         ` Oleg Nesterov
2012-05-09 21:32           ` Suresh Siddha
2012-05-10 16:55             ` Oleg Nesterov
2012-05-10 17:04               ` Linus Torvalds
2012-05-10 23:33                 ` [PATCH v2 1/4] fork: move the real prepare_to_copy() users to arch_dup_task_struct() Suresh Siddha
2012-05-10 23:33                   ` [PATCH v2 2/4] coredump: ensure the fpu state is flushed for proper multi-threaded core dump Suresh Siddha
2012-05-11 16:51                     ` Oleg Nesterov
2012-05-11 19:05                       ` Suresh Siddha
2012-05-13 16:11                         ` Oleg Nesterov
2012-05-15 18:03                           ` Suresh Siddha
2012-05-15 18:55                             ` Oleg Nesterov
2012-05-17  0:17                     ` [tip:x86/fpu] " tip-bot for Suresh Siddha
2012-05-10 23:33                   ` [PATCH v2 3/4] x86, xsave: remove thread_has_fpu() bug check in __sanitize_i387_state() Suresh Siddha
2012-05-17  0:18                     ` [tip:x86/fpu] " tip-bot for Suresh Siddha
2012-05-10 23:33                   ` [PATCH v2 4/4] x86, fpu: drop the fpu state during thread exit Suresh Siddha
2012-05-17  0:19                     ` [tip:x86/fpu] " tip-bot for Suresh Siddha
2012-05-11  0:17                   ` [PATCH v2 1/4] fork: move the real prepare_to_copy() users to arch_dup_task_struct() Benjamin Herrenschmidt
2012-05-17  0:16                   ` [tip:x86/fpu] " tip-bot for Suresh Siddha
2012-05-10 23:48                 ` [PATCH 1/3] coredump: flush the fpu exit state for proper multi-threaded core dump Suresh Siddha
2012-05-08 23:18       ` [PATCH 2/3] x86, xsave: remove thread_has_fpu() bug check in __sanitize_i387_state() Suresh Siddha
2012-05-09 20:30         ` Oleg Nesterov
2012-05-09 21:18           ` Suresh Siddha
2012-05-10 16:36             ` Oleg Nesterov
2012-05-08 23:18       ` [PATCH 3/3] x86, fpu: clear the fpu state during thread exit Suresh Siddha

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