Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Andreas Schwab <schwab@linux-m68k.org>
To:     Christoph Hellwig <hch@infradead.org>
Cc:     Palmer Dabbelt <palmer@sifive.com>,
        linux-riscv@lists.infradead.org,
        Paul Walmsley <paul.walmsley@sifive.com>, marco@decred.org,
        me@carlosedp.com, joel@sing.id.au, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] RISC-V: Break load reservations during switch_to
References: <20190605231735.26581-1-palmer@sifive.com>
        <20190606090518.GB1369@infradead.org>
Date:   Thu, 06 Jun 2019 21:32:01 +0200
In-Reply-To: <20190606090518.GB1369@infradead.org> (Christoph Hellwig's
        message of "Thu, 6 Jun 2019 02:05:18 -0700")
Message-ID: <87ftom4ij2.fsf@igel.home>
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.2 (gnu/linux)
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Jun 06 2019, Christoph Hellwig <hch@infradead.org> wrote:

> On Wed, Jun 05, 2019 at 04:17:35PM -0700, Palmer Dabbelt wrote:
>>  	REG_S ra,  TASK_THREAD_RA_RA(a3)
>> +	/*
>> +	 * The Linux ABI allows programs to depend on load reservations being
>> +	 * broken on context switches, but the ISA doesn't require that the
>> +	 * hardware ever breaks a load reservation.  The only way to break a
>> +	 * load reservation is with a store conditional, so we emit one here.
>> +	 * Since nothing ever takes a load reservation on TASK_THREAD_RA_RA we
>> +	 * know this will always fail, but just to be on the safe side this
>> +	 * writes the same value that was unconditionally written by the
>> +	 * previous instruction.
>> +	 */
>> +#if (TASK_THREAD_RA_RA != 0)
>
> I don't think this check works as intended.  TASK_THREAD_RA_RA is a
> parameterized macro,

Is it?  Just because it is used before an open paren doesn't mean that
the macro takes a parameter.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
"And now for something completely different."