From: Oleg Nesterov <oleg@redhat.com>
To: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: torvalds@linux-foundation.org, hpa@zytor.com, mingo@elte.hu,
linux-kernel@vger.kernel.org, suresh@aristanetworks.com
Subject: Re: [PATCH 2/3] x86, xsave: remove thread_has_fpu() bug check in __sanitize_i387_state()
Date: Wed, 9 May 2012 22:30:47 +0200 [thread overview]
Message-ID: <20120509203047.GA334@redhat.com> (raw)
In-Reply-To: <1336519085-27450-3-git-send-email-suresh.b.siddha@intel.com>
Hi Suresh,
I can't really comment this series, my understanding of this code
is too limited.
But could you explain this patch? I am just curious.
On 05/08, Suresh Siddha wrote:
>
> 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.
And? Do you see any particular scenario when this BUG_ON() is wrong?
Afaics, __sanitize_i387_state() should not be called if the task can
be scheduled in with ->fpu_counter != 0.
> Similarly during core dump, thread dumping the core can schedule out
> and in for page-allocations etc in non-preempt case.
Again, can't understand. The core-dumping thread does init_fpu()
before it calls sanitize_i387_state().
Oleg.
next prev parent reply other threads:[~2012-05-09 20:31 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 ` [PATCH 2/2] x86, xsave: remove thread_has_fpu() bug check in __sanitize_i387_state() Suresh Siddha
2012-05-07 19:15 ` [PATCH 1/2] coredump: flush the fpu exit state for proper multi-threaded core dump 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 [this message]
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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