Messages in this thread | | | From | Michael Ellerman <> | Subject | Re: [PATCH tip/core/rcu 2/3] srcu: Force full grace-period ordering | Date | Mon, 23 Jan 2017 19:12:03 +1100 |
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"Paul E. McKenney" <paulmck@linux.vnet.ibm.com> writes:
> On Sat, Jan 14, 2017 at 11:54:17AM -0800, Paul E. McKenney wrote: >> On Sat, Jan 14, 2017 at 10:35:50AM +0100, Ingo Molnar wrote: >> > * Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote: > > [ . . . ] > >> > > + */ >> > > +#ifdef CONFIG_PPC >> > > +#define smp_mb__after_unlock_lock() smp_mb() /* Full ordering for lock. */ >> > > +#else /* #ifdef CONFIG_PPC */ >> > > +#define smp_mb__after_unlock_lock() do { } while (0) >> > > +#endif /* #else #ifdef CONFIG_PPC */ >> > >> > Yeah, so I realize that this was pre-existing code, but putting CONFIG_$ARCH >> > #ifdefs into generic headers is generally frowned upon. >> > >> > The canonical approach would be either to define a helper Kconfig variable that >> > can be set by PPC (but other architectures don't need to set it), or to expose a >> > suitable macro (function) for architectures to define in their barrier.h arch >> > header file. >> >> Very well, I will add a separate commit for this. 4.11 OK? > > Does the patch below seem reasonable? > > Thanx, Paul > > ------------------------------------------------------------------------ > > commit 271c0601237c41a279f975563e13837bace0df03 > Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > Date: Sat Jan 14 13:32:50 2017 -0800 > > rcu: Make arch select smp_mb__after_unlock_lock() strength > > The definition of smp_mb__after_unlock_lock() is currently smp_mb() > for CONFIG_PPC and a no-op otherwise. It would be better to instead > provide an architecture-selectable Kconfig option, and select the > strength of smp_mb__after_unlock_lock() based on that option. This > commit therefore creates CONFIG_ARCH_WEAK_RELACQ, has PPC select it, > and bases the definition of smp_mb__after_unlock_lock() on this new > CONFIG_ARCH_WEAK_RELACQ Kconfig option. > > Reported-by: Ingo Molnar <mingo@kernel.org> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Will Deacon <will.deacon@arm.com> > Cc: Boqun Feng <boqun.feng@linux.vnet.ibm.com> > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> > Cc: Paul Mackerras <paulus@samba.org> > Cc: Michael Ellerman <mpe@ellerman.id.au> > Cc: <linuxppc-dev@lists.ozlabs.org>
Personally I'd call it ARCH_WEAK_RELEASE_ACQUIRE, which is longer but clearer I think. But it's not a big deal, so which ever you prefer.
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
cheers
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