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[193.116.74.175]) by smtp.gmail.com with ESMTPSA id l64sm3007386pfj.179.2019.03.02.17.47.27 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Sat, 02 Mar 2019 17:47:28 -0800 (PST) Date: Sun, 03 Mar 2019 11:47:22 +1000 From: Nicholas Piggin Subject: Re: [PATCH 03/20] mmiowb: Hook up mmiowb helpers to spinlocks and generic I/O accessors To: linux-arch@vger.kernel.org, Will Deacon Cc: Andrea Parri , Arnd Bergmann , Benjamin Herrenschmidt , Rich Felker , David Howells , Daniel Lustig , linux-kernel@vger.kernel.org, "Maciej W. Rozycki" , Ingo Molnar , Michael Ellerman , Palmer Dabbelt , Paul Burton , "Paul E. McKenney" , Peter Zijlstra , Alan Stern , Tony Luck , Linus Torvalds , Yoshinori Sato References: <20190301140348.25175-1-will.deacon@arm.com> <20190301140348.25175-4-will.deacon@arm.com> In-Reply-To: <20190301140348.25175-4-will.deacon@arm.com> MIME-Version: 1.0 User-Agent: astroid/0.14.0 (https://github.com/astroidmail/astroid) Message-Id: <1551577391.707a6tsmt3.astroid@bobo.none> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Will Deacon's on March 2, 2019 12:03 am: > @@ -177,6 +178,7 @@ do { \ > static inline void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(loc= k) > { > __acquire(lock); > + mmiowb_spin_lock(); > arch_spin_lock(&lock->raw_lock); > } > =20 > @@ -188,16 +190,23 @@ static inline void > do_raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long *flags) __acq= uires(lock) > { > __acquire(lock); > + mmiowb_spin_lock(); > arch_spin_lock_flags(&lock->raw_lock, *flags); > } You'd be better to put these inside the spin lock, to match your=20 trylock. Also it means the mmiowb state can be used inside a lock/unlock pair without a compiler barrer forcing it to be reloaded, should be better code generation for very small critical sections on archs which inline lock and unlock. > =20 > static inline int do_raw_spin_trylock(raw_spinlock_t *lock) > { > - return arch_spin_trylock(&(lock)->raw_lock); > + int ret =3D arch_spin_trylock(&(lock)->raw_lock); > + > + if (ret) > + mmiowb_spin_lock(); > + > + return ret; > } > =20 > static inline void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(l= ock) > { > + mmiowb_spin_unlock(); > arch_spin_unlock(&lock->raw_lock); > __release(lock); > } Thanks, Nick =