Re: [rfc patch v4.4-rt2] sched: fix up preempt lazy forward port

From	Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Newsgroups	linux.kernel
Subject	Re: [rfc patch v4.4-rt2] sched: fix up preempt lazy forward port
Date	2016-02-01 14:10 +0100
Message-ID	<qXmoY-3eN-55@gated-at.bofh.it> (permalink)
References	(1 earlier) <qSorp-5DG-23@gated-at.bofh.it> <qTIxI-3xw-19@gated-at.bofh.it> <qTJtM-497-7@gated-at.bofh.it> <qTQOC-Mq-7@gated-at.bofh.it> <qUSY2-7hD-23@gated-at.bofh.it>
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On 01/25/2016 06:14 PM, Grygorii Strashko wrote:

>> diff --git a/arch/arm/kernel/entry-common.S
>> b/arch/arm/kernel/entry-common.S
>> index 30a7228eaceb..c3bd6cbfce4b 100644
>> --- a/arch/arm/kernel/entry-common.S
>> +++ b/arch/arm/kernel/entry-common.S
>> @@ -36,7 +36,9 @@
>>    UNWIND(.cantunwind    )
>>       disable_irq_notrace            @ disable interrupts
>>       ldr    r1, [tsk, #TI_FLAGS]        @ re-check for syscall tracing
>> -    tst    r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK
>> +    tst    r1, #((_TIF_SYSCALL_WORK | _TIF_WORK_MASK) & ~_TIF_SECCOMP)
>> +    bne    fast_work_pending
>         ^^^^^^^^^^^^^^^^
> 
>> +    tst    r1, #_TIF_SECCOMP
>>       bne    fast_work_pending
>         ^^^^^^^^^^^^^^^^^
> 
> Should it be "fast_work_pending" in both cases?

Yes, I think so and it is, isn't it?
The original is

     tst    r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK
     bne    fast_work_pending

and with the LAZY bits in it, the ASM opcode no longer works because
the constant is too large (or has to many bits set). So I removed the
_TIF_SECCOMP bit out of the mask and made two compare & jumps here.

Sebastian

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Re: [rfc patch v4.4-rt2] sched: fix up preempt lazy forward port Sebastian Andrzej Siewior <bigeasy@linutronix.de> - 2016-02-01 14:10 +0100

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