linux-kernel - Re: [FOR REVIEW, PATCH 2/2] introduce "struct wait_opts" to simplify do

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Message-Id: <20090507072003.8E0ACFC39E@magilla.sf.frob.com>
Date:	Thu,  7 May 2009 00:20:03 -0700 (PDT)
From:	Roland McGrath <roland@...hat.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [FOR REVIEW, PATCH 2/2] introduce "struct wait_opts" to
	simplify do_wait() pathes

> Yes, I considered this option too. But since (I hope) you do not have
> a strong opinion on this, I'd prefer to keep the code as is. This way
> do_wait() looks more symmetrical wrt to other helpers. And we don't
> copy args twice.

I don't feel strongly.  But I do think that those two repeated assignment
blocks are more to read and harder to read, and more error-prone for drift
in future changes (vs prototype changes getting quick compilation errors).
do_wait() is not "another helper", it's the main function.  On machines
with 6 argument registers (everything but x86-32?), the compiler probably
does fine making the callers' register shuffling be free.  On x86-32, a few
cache-hot stack stores and loads are in the tiny noise vs the whole cost of
this hairy syscall, and IMHO don't compare to source maintainability issues.

Thanks,
Roland
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