From: Bobby Powers <bobbypowers@gmail.com>
To: Oleg Nesterov <oleg@redhat.com>, Ingo Molnar <mingo@kernel.org>
Cc: Kernel development list <linux-kernel@vger.kernel.org>,
x86@kernel.org, Andi Kleen <ak@linux.intel.com>,
Borislav Petkov <bp@suse.de>,
Andy Lutomirski <luto@amacapital.net>,
Dave Hansen <dave.hansen@intel.com>,
Fenghua Yu <fenghua.yu@intel.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Pekka Riikonen <priikone@iki.fi>,
Quentin Casasnovas <quentin.casasnovas@oracle.com>,
Rik van Riel <riel@redhat.com>,
Suresh Siddha <sbsiddha@gmail.com>
Subject: Re: [PATCH v2] x86/fpu: always restore_xinit_state() when use_eager_cpu()
Date: Sat, 2 May 2015 16:42:59 -0400 [thread overview]
Message-ID: <CAArOQ2U7fZyEGEbmXW5Ge1E1_fVCruOA-YLSLpY04jPxYUehKQ@mail.gmail.com> (raw)
In-Reply-To: <20150427151946.GA28094@redhat.com>
Hello,
Oleg Nesterov <oleg@redhat.com> wrote:
> Thanks!
Dave gave this his:
Tested-By: Dave Hansen <dave.hansen@intel.com>
over under v1 of this patch:
https://lkml.kernel.org/g/5543C277.9070208@intel.com
Anything else anyone sees, or anyone in particular I have to poke at
to get this in? Ingo?
yours,
Bobby
On Mon, Apr 27, 2015 at 11:19 AM, Oleg Nesterov <oleg@redhat.com> wrote:
> Thanks!
>
> On 04/27, Bobby Powers wrote:
>>
>> v2: switch used_math() -> tsk_used_math(tsk) to consistently use the
>> grabbed tsk instead of current, like in the rest of flush_thread().
>>
>> Oleg's commit f893959b ("x86/fpu: Don't abuse drop_init_fpu() in
>> flush_thread()") removed drop_init_fpu() usage from flush_thread.
>> This seems to break things for me - the Go 1.4 test suite fails all
>> over the place with floating point comparision errors (offending
>> commit found through bisection).
>>
>> The functional change was that flush_thread after f893959b only calls
>> restore_init_xstate when both use_eager_fpu() and !used_math() are
>> true. drop_init_fpu (now fpu_reset_state) calls restore_init_xstate()
>> regardless of whether current used_math() - apply the same logic here.
>>
>> Fixes: f893959b ("x86/fpu: Don't abuse drop_init_fpu() in flush_thread()")
>> Signed-off-by: Bobby Powers <bobbypowers@gmail.com>
>> Acked-by: Oleg Nesterov <oleg@redhat.com>
>> Cc: Andi Kleen <ak@linux.intel.com>
>> Cc: Borislav Petkov <bp@suse.de>
>> Cc: Ingo Molnar <mingo@kernel.org>
>> Cc: Andy Lutomirski <luto@amacapital.net>
>> Cc: Dave Hansen <dave.hansen@intel.com>
>> Cc: Fenghua Yu <fenghua.yu@intel.com>
>> Cc: Linus Torvalds <torvalds@linux-foundation.org>
>> Cc: Pekka Riikonen <priikone@iki.fi>
>> Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
>> Cc: Rik van Riel <riel@redhat.com>
>> Cc: Suresh Siddha <sbsiddha@gmail.com>
>> ---
>> arch/x86/kernel/process.c | 12 +++++++-----
>> 1 file changed, 7 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
>> index 8213da6..1a6fcf8 100644
>> --- a/arch/x86/kernel/process.c
>> +++ b/arch/x86/kernel/process.c
>> @@ -156,11 +156,13 @@ void flush_thread(void)
>> /* FPU state will be reallocated lazily at the first use. */
>> drop_fpu(tsk);
>> free_thread_xstate(tsk);
>> - } else if (!used_math()) {
>> - /* kthread execs. TODO: cleanup this horror. */
>> - if (WARN_ON(init_fpu(tsk)))
>> - force_sig(SIGKILL, tsk);
>> - user_fpu_begin();
>> + } else {
>> + if (!tsk_used_math(tsk)) {
>> + /* kthread execs. TODO: cleanup this horror. */
>> + if (WARN_ON(init_fpu(tsk)))
>> + force_sig(SIGKILL, tsk);
>> + user_fpu_begin();
>> + }
>> restore_init_xstate();
>> }
>> }
>> --
>> 2.3.6
>>
>
next prev parent reply other threads:[~2015-05-02 20:43 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-26 22:04 [PATCH] x86/fpu: always restore_xinit_state() when !use_eager_cpu() Bobby Powers
2015-04-27 14:46 ` Dave Hansen
2015-04-27 15:00 ` Oleg Nesterov
2015-05-01 18:14 ` Dave Hansen
2015-04-27 14:49 ` Oleg Nesterov
2015-04-27 14:58 ` Bobby Powers
2015-04-27 15:10 ` [PATCH v2] x86/fpu: always restore_xinit_state() when use_eager_cpu() Bobby Powers
2015-04-27 15:19 ` Oleg Nesterov
2015-05-02 20:42 ` Bobby Powers [this message]
2015-05-03 17:39 ` Oleg Nesterov
2015-05-04 8:11 ` Borislav Petkov
2015-05-06 10:14 ` [tip:x86/urgent] x86/fpu: Always " tip-bot for Bobby Powers
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