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[109.80.100.86]) by smtp.gmail.com with ESMTPSA id m10sm9287874wmf.40.2019.05.23.01.30.20 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 23 May 2019 01:30:21 -0700 (PDT) Date: Thu, 23 May 2019 10:30:13 +0200 From: Andrea Parri To: Mark Rutland Cc: linux-kernel@vger.kernel.org, peterz@infradead.org, will.deacon@arm.com, aou@eecs.berkeley.edu, arnd@arndb.de, bp@alien8.de, catalin.marinas@arm.com, davem@davemloft.net, fenghua.yu@intel.com, heiko.carstens@de.ibm.com, herbert@gondor.apana.org.au, ink@jurassic.park.msu.ru, jhogan@kernel.org, linux@armlinux.org.uk, mattst88@gmail.com, mingo@kernel.org, mpe@ellerman.id.au, palmer@sifive.com, paul.burton@mips.com, paulus@samba.org, ralf@linux-mips.org, rth@twiddle.net, stable@vger.kernel.org, tglx@linutronix.de, tony.luck@intel.com, vgupta@synopsys.com Subject: Re: [PATCH 00/18] locking/atomic: atomic64 type cleanup Message-ID: <20190523083013.GA4616@andrea> References: <20190522132250.26499-1-mark.rutland@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190522132250.26499-1-mark.rutland@arm.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org Hi Mark, On Wed, May 22, 2019 at 02:22:32PM +0100, Mark Rutland wrote: > Currently architectures return inconsistent types for atomic64 ops. Some return > long (e..g. powerpc), some return long long (e.g. arc), and some return s64 > (e.g. x86). (only partially related, but probably worth asking:) While reading the series, I realized that the following expression: atomic64_t v; ... typeof(v.counter) my_val = atomic64_set(&v, VAL); is a valid expression on some architectures (in part., on architectures which #define atomic64_set() to WRITE_ONCE()) but is invalid on others. (This is due to the fact that WRITE_ONCE() can be used as an rvalue in the above assignment; TBH, I ignore the reasons for having such rvalue?) IIUC, similar considerations hold for atomic_set(). The question is whether this is a known/"expected" inconsistency in the implementation of atomic64_set() or if this would also need to be fixed /addressed (say in a different patchset)? Thanks, Andrea