linux-kernel - Re: [PATCH] jump label: Add MIPS support.

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Message-ID: <4CAA122B.40502@caviumnetworks.com>
Date:	Mon, 04 Oct 2010 10:43:07 -0700
From:	David Daney <ddaney@...iumnetworks.com>
To:	Rabin Vincent <rabin@....in>
CC:	linux-mips@...ux-mips.org, ralf@...ux-mips.org,
	linux-kernel@...r.kernel.org, rostedt@...dmis.org,
	jbaron@...hat.com, David Miller <davem@...emloft.net>
Subject: Re: [PATCH] jump label: Add MIPS support.

On 10/03/2010 11:15 AM, Rabin Vincent wrote:
> On Tue, Sep 28, 2010 at 11:40 PM, David Daney<ddaney@...iumnetworks.com>  wrote:
>> +void arch_jump_label_text_poke_early(jump_label_t addr)
>> +{
>> +       union mips_instruction *insn_p =
>> +               (union mips_instruction *)(unsigned long)addr;
>> +
>> +       insn_p->word = 0; /* nop */
>> +       flush_icache_range((unsigned long)insn_p,
>> +                          (unsigned long)insn_p + sizeof(*insn_p));
>> +}
>
> Can't this function be a no-op on MIPS?  This seems to be
> used on x86 to patch in the optimal nop instruction, but
> on MIPS the optimal/only nop instruction should already
> be in place at build time.  Same thing for the SPARC
> implementation.
>

Yes, I think you are correct.

On MIPS the NOP is already optimal.  I will respin the MIPS patch to 
make arch_jump_label_text_poke_early() be empty.

davem wasn't CCed on the original message, so I added him.  I would 
defer to him on the SPARC version.


Thanks,
David Daney
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