linux-kernel - Re: [PATCH 000/208] big x86 FPU code rewrite

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Date:	Fri, 29 May 2015 20:53:59 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Dave Hansen <dave.hansen@...ux.intel.com>
Cc:	linux-kernel@...r.kernel.org,
	Andy Lutomirski <luto@...capital.net>,
	Borislav Petkov <bp@...en8.de>,
	Fenghua Yu <fenghua.yu@...el.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 000/208] big x86 FPU code rewrite


* Dave Hansen <dave.hansen@...ux.intel.com> wrote:

> Hey Ingo,
> 
> This throws a warning if I try to run one of my MPX programs:
> 
> > [   22.907739] ------------[ cut here ]------------
> > [   22.907776] WARNING: CPU: 0 PID: 500 at /home/davehans/linux.git/arch/x86/kernel/fpu/core.c:324 fpu__activate_stopped+0x87/0x90()
> > [   22.907836] Modules linked in:
> > [   22.907859] CPU: 0 PID: 500 Comm: mpx-mini-test-v Not tainted 4.1.0-rc2-00208-ga9a0b36 #1181
> > [   22.907901] Hardware name: Intel Corporation 
> > [   22.907958]  ffffffff81c5e4d0 ffff880166bff988 ffffffff817fb4de 0000000000000000
> > [   22.908005]  0000000000000000 ffff880166bff9c8 ffffffff810a7dca ffff880166bff9d8
> > [   22.908049]  ffff8800728d40c0 0000000000000200 0000000000000000 ffff88007b3fec00
> > [   22.908093] Call Trace:
> > [   22.908109]  [<ffffffff817fb4de>] dump_stack+0x4c/0x65
> > [   22.908139]  [<ffffffff810a7dca>] warn_slowpath_common+0x8a/0xc0
> > [   22.908169]  [<ffffffff810a7eba>] warn_slowpath_null+0x1a/0x20
> > [   22.908201]  [<ffffffff81061eb7>] fpu__activate_stopped+0x87/0x90
> > [   22.908230]  [<ffffffff810623c5>] xfpregs_get+0x35/0xa0
> > [   22.908257]  [<ffffffff8123535c>] elf_core_dump+0x56c/0x1600
> > [   22.908289]  [<ffffffff817f95ed>] ? __slab_free+0x10a/0x212
> > [   22.908318]  [<ffffffff8123e3eb>] do_coredump+0x78b/0xe90
> > [   22.908346]  [<ffffffff810b2747>] ? __sigqueue_free.part.16+0x37/0x40
> > [   22.908379]  [<ffffffff810b5c33>] get_signal+0x1d3/0x640
> > [   22.908407]  [<ffffffff810b409e>] ? send_signal+0x3e/0x80
> > [   22.908434]  [<ffffffff81056478>] do_signal+0x28/0x6c0
> > [   22.908464]  [<ffffffff810d6ca9>] ? pick_next_entity+0xa9/0x190
> > [   22.908488]  [<ffffffff810b4c45>] ? do_send_specific+0x85/0xa0
> > [   22.908521]  [<ffffffff81056b88>] do_notify_resume+0x78/0x80
> > [   22.908549]  [<ffffffff81803282>] int_signal+0x12/0x17
> > [   22.908575] ---[ end trace 80f689a9062056c5 ]---
> 
> This is booted with or without xsaves support.

Could you check latest -tip, whether this warning still occurs?

It should be fixed by:

  47f01e8cc23f ("x86/fpu: Fix FPU register read access to the current task")

Thanks,

	Ingo
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