Date: Tue, 16 Jul 2019 17:07:57 -0700 From: "Paul E. McKenney" <paulmck@...ux.ibm.com> To: Joel Fernandes <joel@...lfernandes.org> Cc: linux-kernel@...r.kernel.org, Alexey Kuznetsov <kuznet@....inr.ac.ru>, Bjorn Helgaas <bhelgaas@...gle.com>, Borislav Petkov <bp@...en8.de>, c0d1n61at3@...il.com, "David S. Miller" <davem@...emloft.net>, edumazet@...gle.com, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>, "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>, Jonathan Corbet <corbet@....net>, Josh Triplett <josh@...htriplett.org>, keescook@...omium.org, kernel-hardening@...ts.openwall.com, kernel-team@...roid.com, Lai Jiangshan <jiangshanlai@...il.com>, Len Brown <lenb@...nel.org>, linux-acpi@...r.kernel.org, linux-doc@...r.kernel.org, linux-pci@...r.kernel.org, linux-pm@...r.kernel.org, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, neilb@...e.com, netdev@...r.kernel.org, Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>, peterz@...radead.org, "Rafael J. Wysocki" <rjw@...ysocki.net>, Rasmus Villemoes <rasmus.villemoes@...vas.dk>, rcu@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>, Tejun Heo <tj@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, will@...nel.org, "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org> Subject: Re: [PATCH 2/9] rcu: Add support for consolidated-RCU reader checking (v3) On Tue, Jul 16, 2019 at 06:02:05PM -0400, Joel Fernandes wrote: > On Tue, Jul 16, 2019 at 11:53:03AM -0700, Paul E. McKenney wrote: > [snip] > > > > A few more things below. > > > > > --- > > > > > include/linux/rculist.h | 28 ++++++++++++++++++++----- > > > > > include/linux/rcupdate.h | 7 +++++++ > > > > > kernel/rcu/Kconfig.debug | 11 ++++++++++ > > > > > kernel/rcu/update.c | 44 ++++++++++++++++++++++++---------------- > > > > > 4 files changed, 67 insertions(+), 23 deletions(-) > > > > > > > > > > diff --git a/include/linux/rculist.h b/include/linux/rculist.h > > > > > index e91ec9ddcd30..1048160625bb 100644 > > > > > --- a/include/linux/rculist.h > > > > > +++ b/include/linux/rculist.h > > > > > @@ -40,6 +40,20 @@ static inline void INIT_LIST_HEAD_RCU(struct list_head *list) > > > > > */ > > > > > #define list_next_rcu(list) (*((struct list_head __rcu **)(&(list)->next))) > > > > > > > > > > +/* > > > > > + * Check during list traversal that we are within an RCU reader > > > > > + */ > > > > > + > > > > > +#ifdef CONFIG_PROVE_RCU_LIST > > > > > > > > This new Kconfig option is OK temporarily, but unless there is reason to > > > > fear malfunction that a few weeks of rcutorture, 0day, and -next won't > > > > find, it would be better to just use CONFIG_PROVE_RCU. The overall goal > > > > is to reduce the number of RCU knobs rather than grow them, must though > > > > history might lead one to believe otherwise. :-/ > > > > > > If you want, we can try to drop this option and just use PROVE_RCU however I > > > must say there may be several warnings that need to be fixed in a short > > > period of time (even a few weeks may be too short) considering the 1000+ > > > uses of RCU lists. > > Do many people other than me build with CONFIG_PROVE_RCU? If so, then > > that would be a good reason for a temporary CONFIG_PROVE_RCU_LIST, > > as in going away in a release or two once the warnings get fixed. > > PROVE_RCU is enabled by default with PROVE_LOCKING, so it is used quite > heavilty. > > > > But I don't mind dropping it and it may just accelerate the fixing up of all > > > callers. > > > > I will let you decide based on the above question. But if you have > > CONFIG_PROVE_RCU_LIST, as noted below, it needs to depend on RCU_EXPERT. > > Ok, will make it depend. But yes for temporary purpose, I will leave it as a > config and remove it later. Very good, thank you! Plus you got another ack. ;-) Thanx, Paul
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