linux-kernel - Re: [RESEND] [RFC][PATCH X86_32 1/2]: Call do_notify

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Date:	Wed, 26 Oct 2011 14:38:39 +0200
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Christoph Hellwig <hch@...radead.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	Roland McGrath <roland@...k.frob.com>,
	Shuah Khan <shuah.khan@...com>, Ingo Molnar <mingo@...e.hu>,
	Alexander van Heukelum <heukelum@...tmail.fm>,
	Russell King <rmk@....linux.org.uk>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RESEND] [RFC][PATCH X86_32 1/2]: Call do_notify_resume() with
 interrupts enabled

Ingo, Thomas, I think this is your call, but it seems valid,

                 Linus

On Tue, Oct 25, 2011 at 6:14 PM, Oleg Nesterov <oleg@...hat.com> wrote:
> On 10/25, Srikar Dronamraju wrote:
>>
>> do_notify_resume() gets called with interrupts disabled on x86_32. This
>> is different from the x86_64 behavior, where interrupts are enabled at
>> the time.
>
> And note that do_notify_resume() paths assume that irqs are enabled.
> key_replace_session_keyring/get_signal_to_deliver start with _lock_irq.
>
> IOW, I vote for this change even if I can't ack it (although it looks
> "obviously correct" to me). In fact refrigerator() looks buggy without
> this change. Yes, it enables irqs but only "by accident", via unlock_irq().
> And we are going to remove this recalc_sigpending() from freezer.
>
>
>> Queries on lkml on this issue hasn't yielded any clear answer. Lets make
>> x86_32 behave the same as x86_64, unless there is a real reason to
>> maintain status quo.
>>
>> Please refer https://lkml.org/lkml/2011/9/27/130 for more details
>>
>> A similar change was suggested in arm
>>       https://lkml.org/lkml/2011/8/25/231
>>
>> My 32-bit machine works fine (tm) with the patch below
>>
>> Signed-off-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
>> ---
>>  arch/x86/kernel/entry_32.S |    4 ++++
>>  1 files changed, 4 insertions(+)
>>
>> diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
>> index f3f6f53..22d0e21 100644
>> --- a/arch/x86/kernel/entry_32.S
>> +++ b/arch/x86/kernel/entry_32.S
>> @@ -625,6 +625,8 @@ work_notifysig:                           # deal with pending signals and
>>       movl %esp, %eax
>>       jne work_notifysig_v86          # returning to kernel-space or
>>                                       # vm86-space
>> +     TRACE_IRQS_ON
>> +     ENABLE_INTERRUPTS(CLBR_NONE)
>>       xorl %edx, %edx
>>       call do_notify_resume
>>       jmp resume_userspace_sig
>> @@ -638,6 +640,8 @@ work_notifysig:                           # deal with pending signals and
>>  #else
>>       movl %esp, %eax
>>  #endif
>> +     TRACE_IRQS_ON
>> +     ENABLE_INTERRUPTS(CLBR_NONE)
>>       xorl %edx, %edx
>>       call do_notify_resume
>>       jmp resume_userspace_sig
>>
>
>
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