From: Rik van Riel <riel@redhat.com>
To: Oleg Nesterov <oleg@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Suresh Siddha <sbsiddha@gmail.com>
Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, hpa@zytor.com,
matt.fleming@intel.com, bp@suse.de, pbonzini@redhat.com,
tglx@linutronix.de, luto@amacapital.net
Subject: Re: [PATCH 1/3] x86, fpu: __kernel_fpu_begin() should clear fpu_owner_task even if use_eager_fpu()
Date: Tue, 20 Jan 2015 09:15:42 -0500 [thread overview]
Message-ID: <54BE630E.4000901@redhat.com> (raw)
In-Reply-To: <20150119185132.GB16427@redhat.com>
On 01/19/2015 01:51 PM, Oleg Nesterov wrote:
> __kernel_fpu_begin() does nothing if !__thread_has_fpu() && use_eager_fpu(),
> perhaps it assumes that this case is simply impossible. This is certainly
> not possible if in_interrupt() == T; interrupted_user_mode() should have
> FPU, and interrupted_kernel_fpu_idle() should fail if !__thread_has_fpu().
>
> However, even if use_eager_fpu() == T a task can do drop_fpu(), then switch
> to another thread which becomes fpu_owner_task, then resume and call some
> function which does kernel_fpu_begin(). Say, an exiting task does a lot of
> things after exit_thread(), it is not safe to assume that it can't use FPU
> in these paths.
>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
next prev parent reply other threads:[~2015-01-20 14:16 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-11 21:46 [RFC PATCH 0/11 BROKEN] move FPU context loading to userspace switch riel
2015-01-11 21:46 ` [RFC PATCH 01/11] x86,fpu: document the data structures a little riel
2015-01-12 21:18 ` Borislav Petkov
2015-01-12 21:38 ` Rik van Riel
2015-01-12 21:52 ` Dave Hansen
2015-01-13 15:59 ` Rik van Riel
2015-01-11 21:46 ` [RFC PATCH 02/11] x86,fpu: replace fpu_switch_t with a thread flag riel
2015-01-13 15:24 ` Oleg Nesterov
2015-01-13 16:35 ` Rik van Riel
2015-01-13 16:55 ` Oleg Nesterov
2015-01-11 21:46 ` [RFC PATCH 03/11] x86,fpu: move __thread_fpu_begin to when the task has the fpu riel
2015-01-13 15:24 ` Oleg Nesterov
2015-01-13 16:37 ` Rik van Riel
2015-01-11 21:46 ` [RFC PATCH 04/11] x86,fpu: defer FPU restore until return to userspace riel
2015-01-13 15:53 ` Oleg Nesterov
2015-01-13 17:07 ` Andy Lutomirski
2015-01-13 17:11 ` Oleg Nesterov
2015-01-13 17:18 ` Andy Lutomirski
2015-01-13 17:44 ` Rik van Riel
2015-01-13 17:57 ` Andy Lutomirski
2015-01-13 18:13 ` Rik van Riel
2015-01-13 18:26 ` Andy Lutomirski
2015-01-13 17:54 ` Rik van Riel
2015-01-13 18:22 ` Oleg Nesterov
2015-01-13 18:30 ` Oleg Nesterov
2015-01-13 20:06 ` Rik van Riel
2015-01-14 17:56 ` Oleg Nesterov
2015-01-13 17:58 ` Oleg Nesterov
2015-01-13 19:32 ` Rik van Riel
2015-01-11 21:46 ` [RFC PATCH 05/11] x86,fpu: ensure FPU state is reloaded from memory if task is traced riel
2015-01-13 16:19 ` Oleg Nesterov
2015-01-13 16:33 ` Rik van Riel
2015-01-13 16:50 ` Oleg Nesterov
2015-01-13 16:57 ` Rik van Riel
2015-01-11 21:46 ` [RFC PATCH 06/11] x86,fpu: lazily skip fpu restore with eager fpu mode, too riel
2015-01-13 17:11 ` Andy Lutomirski
2015-01-13 20:43 ` Rik van Riel
2015-01-14 18:36 ` Oleg Nesterov
2015-01-15 2:49 ` Rik van Riel
2015-01-15 19:34 ` Oleg Nesterov
2015-01-11 21:46 ` [RFC PATCH 07/11] x86,fpu: store current fpu pointer, instead of fpu_owner_task riel
2015-01-11 21:46 ` [RFC PATCH 08/11] x86,fpu: restore user FPU state lazily after __kernel_fpu_end riel
2015-01-14 18:43 ` Oleg Nesterov
2015-01-14 19:08 ` Oleg Nesterov
2015-01-11 21:46 ` [RFC PATCH 09/11] x86,fpu,kvm: keep vcpu FPU active as long as it is resident riel
2015-01-11 21:46 ` [RFC PATCH 10/11] x86,fpu: fix fpu_copy to deal with not-loaded fpu riel
2015-01-11 21:46 ` [RFC PATCH 11/11] (BROKEN) x86,fpu: broken signal handler stack setup riel
2015-01-15 19:19 ` [PATCH 0/3] x86, fpu: kernel_fpu_begin/end initial cleanups/fix Oleg Nesterov
2015-01-15 19:19 ` [PATCH 1/3] x86, fpu: introduce per-cpu "bool in_kernel_fpu" Oleg Nesterov
2015-01-16 2:22 ` Rik van Riel
2015-01-20 12:54 ` [tip:x86/fpu] x86, fpu: Introduce per-cpu in_kernel_fpu state tip-bot for Oleg Nesterov
2015-01-15 19:20 ` [PATCH 2/3] x86, fpu: don't abuse ->has_fpu in __kernel_fpu_{begin,end}() Oleg Nesterov
2015-01-16 2:27 ` Rik van Riel
2015-01-16 15:54 ` Oleg Nesterov
2015-01-16 16:07 ` Rik van Riel
2015-01-20 12:55 ` [tip:x86/fpu] x86, fpu: Don't abuse has_fpu in __kernel_fpu_begin /end() tip-bot for Oleg Nesterov
2015-01-15 19:20 ` [PATCH 3/3] x86, fpu: fix math_state_restore() race with kernel_fpu_begin() Oleg Nesterov
2015-01-16 2:30 ` Rik van Riel
2015-01-16 16:03 ` Oleg Nesterov
2015-01-20 12:55 ` [tip:x86/fpu] x86, fpu: Fix " tip-bot for Oleg Nesterov
2015-01-19 18:51 ` [PATCH 0/3] x86, fpu: more eagerfpu cleanups Oleg Nesterov
2015-01-19 18:51 ` [PATCH 1/3] x86, fpu: __kernel_fpu_begin() should clear fpu_owner_task even if use_eager_fpu() Oleg Nesterov
2015-01-20 14:15 ` Rik van Riel [this message]
2015-02-20 18:13 ` Borislav Petkov
2015-03-03 11:27 ` [tip:x86/fpu] x86/fpu: " tip-bot for Oleg Nesterov
2015-01-19 18:51 ` [PATCH 2/3] x86, fpu: always allow FPU in interrupt " Oleg Nesterov
2015-01-20 14:46 ` Rik van Riel
2015-01-20 22:46 ` Andy Lutomirski
2015-02-20 21:48 ` Borislav Petkov
2015-03-03 11:28 ` [tip:x86/fpu] x86/fpu: Always " tip-bot for Oleg Nesterov
2015-01-19 18:52 ` [PATCH 3/3] x86, fpu: don't abuse FPU in kernel threads " Oleg Nesterov
2015-01-20 14:53 ` Rik van Riel
2015-02-23 15:31 ` Borislav Petkov
2015-03-03 11:28 ` [tip:x86/fpu] x86/fpu: Don' t " tip-bot for Oleg Nesterov
2015-02-20 12:10 ` [PATCH 0/3] x86, fpu: more eagerfpu cleanups Borislav Petkov
2015-02-20 13:30 ` Oleg Nesterov
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