linux-kernel - Re: [PATCH V3 2/3] efi: Introduce efi_queue_work() to queue any efi_runtime_service() on efi_rts

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Message-ID: <20180522073618.GN12198@hirez.programming.kicks-ass.net>
Date:   Tue, 22 May 2018 09:36:18 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Sai Praneeth Prakhya <sai.praneeth.prakhya@...el.com>
Cc:     linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Lee Chun-Yi <jlee@...e.com>, Borislav Petkov <bp@...en8.de>,
        Tony Luck <tony.luck@...el.com>,
        Will Deacon <will.deacon@....com>,
        Dave Hansen <dave.hansen@...el.com>,
        Mark Rutland <mark.rutland@....com>,
        Bhupesh Sharma <bhsharma@...hat.com>,
        Naresh Bhat <naresh.bhat@...aro.org>,
        Ricardo Neri <ricardo.neri@...el.com>,
        Ravi Shankar <ravi.v.shankar@...el.com>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Dan Williams <dan.j.williams@...el.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
Subject: Re: [PATCH V3 2/3] efi: Introduce efi_queue_work() to queue any
 efi_runtime_service() on efi_rts_wq

On Mon, May 21, 2018 at 08:13:03PM -0700, Sai Praneeth Prakhya wrote:
> +	/*								\
> +	 * queue_work() returns 0 if work was already on queue,         \
> +	 * _ideally_ this should never happen.                          \
> +	 */								\
> +	if (queue_work(efi_rts_wq, &efi_rts_work.work))			\
> +		flush_work(&efi_rts_work.work);				\

Since you're _always_ going to wait for it, it is _much_ cheaper to put
a completion in your actual work and wait for that.