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From: Steven Rostedt <rostedt@goodmis.org>
To: Joel Fernandes <joel@joelfernandes.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	linux-kernel@vger.kernel.org,
	Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Borislav Petkov <bp@alien8.de>,
	"David S. Miller" <davem@davemloft.net>,
	edumazet@google.com,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
	"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
	Josh Triplett <josh@joshtriplett.org>,
	keescook@chromium.org, kernel-hardening@lists.openwall.com,
	Lai Jiangshan <jiangshanlai@gmail.com>,
	Len Brown <lenb@kernel.org>,
	linux-acpi@vger.kernel.org, linux-pci@vger.kernel.org,
	linux-pm@vger.kernel.org,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	neilb@suse.com, netdev@vger.kernel.org, oleg@redhat.com,
	"Paul E. McKenney" <paulmck@linux.ibm.com>,
	Pavel Machek <pavel@ucw.cz>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	rcu@vger.kernel.org, Tejun Heo <tj@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
	<x86@kernel.org>
Subject: Re: [RFC 1/6] rcu: Add support for consolidated-RCU reader checking
Date: Tue, 4 Jun 2019 06:53:58 -0400
Message-ID: <20190604065358.73347ced@oasis.local.home> (raw)
In-Reply-To: <20190603141847.GA94186@google.com>

On Mon, 3 Jun 2019 10:18:47 -0400
Joel Fernandes <joel@joelfernandes.org> wrote:

> On Mon, Jun 03, 2019 at 10:01:28AM +0200, Peter Zijlstra wrote:
> > On Sat, Jun 01, 2019 at 06:27:33PM -0400, Joel Fernandes (Google) wrote:  
> > > +#define list_for_each_entry_rcu(pos, head, member, cond...)		\
> > > +	if (COUNT_VARGS(cond) != 0) {					\
> > > +		__list_check_rcu_cond(0, ## cond);			\
> > > +	} else {							\
> > > +		__list_check_rcu();					\
> > > +	}								\
> > > +	for (pos = list_entry_rcu((head)->next, typeof(*pos), member);	\
> > > +		&pos->member != (head);					\
> > >  		pos = list_entry_rcu(pos->member.next, typeof(*pos), member))
> > >  
> > >  /**
> > > @@ -621,7 +648,12 @@ static inline void hlist_add_behind_rcu(struct hlist_node *n,
> > >   * the _rcu list-mutation primitives such as hlist_add_head_rcu()
> > >   * as long as the traversal is guarded by rcu_read_lock().
> > >   */
> > > +#define hlist_for_each_entry_rcu(pos, head, member, cond...)		\
> > > +	if (COUNT_VARGS(cond) != 0) {					\
> > > +		__list_check_rcu_cond(0, ## cond);			\
> > > +	} else {							\
> > > +		__list_check_rcu();					\
> > > +	}								\
> > >  	for (pos = hlist_entry_safe (rcu_dereference_raw(hlist_first_rcu(head)),\
> > >  			typeof(*(pos)), member);			\
> > >  		pos;							\  
> > 
> > 
> > This breaks code like:
> > 
> > 	if (...)
> > 		list_for_each_entry_rcu(...);
> > 
> > as they are no longer a single statement. You'll have to frob it into
> > the initializer part of the for statement.  
> 
> Thanks a lot for that. I fixed it as below (diff is on top of the patch):
> 
> If not for that '##' , I could have abstracted the whole if/else
> expression into its own macro and called it from list_for_each_entry_rcu() to
> keep it more clean.
> 
> ---8<-----------------------
> 
> diff --git a/include/linux/rculist.h b/include/linux/rculist.h
> index b641fdd9f1a2..cc742d294bb0 100644
> --- a/include/linux/rculist.h
> +++ b/include/linux/rculist.h
> @@ -371,12 +372,15 @@ static inline void list_splice_tail_init_rcu(struct list_head *list,
>   * as long as the traversal is guarded by rcu_read_lock().
>   */
>  #define list_for_each_entry_rcu(pos, head, member, cond...)		\
> -	if (COUNT_VARGS(cond) != 0) {					\
> -		__list_check_rcu_cond(0, ## cond);			\
> -	} else {							\
> -		__list_check_rcu();					\
> -	}								\
> -	for (pos = list_entry_rcu((head)->next, typeof(*pos), member);	\
> +	for (								\
> +	     ({								\
> +		if (COUNT_VARGS(cond) != 0) {				\
> +			__list_check_rcu_cond(0, ## cond);		\
> +		} else {						\
> +			__list_check_rcu_nocond();			\
> +		}							\
> +	      }),							\

For easier to read I would do something like this:

#define check_rcu_list(cond)						\
	({								\
		if (COUNT_VARGS(cond) != 0)				\
			__list_check_rcu_cond(0, ## cond);		\
		else							\
			__list_check_rcu_nocond();			\
	})

#define list_for_each_entry_rcu(pos, head, member, cond...)		\
	for (check_rcu_list(cond),					\


-- Steve

> +	     pos = list_entry_rcu((head)->next, typeof(*pos), member);	\
>  		&pos->member != (head);					\
>  		pos = list_entry_rcu(pos->member.next, typeof(*pos), member))
>  
> @@ -649,12 +653,15 @@ static inline void hlist_add_behind_rcu(struct hlist_node *n,
>   * as long as the traversal is guarded by rcu_read_lock().
>   */
>  #define hlist_for_each_entry_rcu(pos, head, member, cond...)		\
> -	if (COUNT_VARGS(cond) != 0) {					\
> -		__list_check_rcu_cond(0, ## cond);			\
> -	} else {							\
> -		__list_check_rcu();					\
> -	}								\
> -	for (pos = hlist_entry_safe (rcu_dereference_raw(hlist_first_rcu(head)),\
> +	for (								\
> +	     ({								\
> +		if (COUNT_VARGS(cond) != 0) {				\
> +			__list_check_rcu_cond(0, ## cond);		\
> +		} else {						\
> +			__list_check_rcu_nocond();			\
> +		}							\
> +	     }),							\
> +	     pos = hlist_entry_safe (rcu_dereference_raw(hlist_first_rcu(head)),\
>  			typeof(*(pos)), member);			\
>  		pos;							\
>  		pos = hlist_entry_safe(rcu_dereference_raw(hlist_next_rcu(\


  parent reply index

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-01 22:27 [RFC 0/6] Harden list_for_each_entry_rcu() and family Joel Fernandes (Google)
2019-06-01 22:27 ` [RFC 1/6] rcu: Add support for consolidated-RCU reader checking Joel Fernandes (Google)
2019-06-03  8:01   ` Peter Zijlstra
2019-06-03 14:18     ` Joel Fernandes
2019-06-03 19:42       ` Joel Fernandes
2019-06-04 10:53       ` Steven Rostedt [this message]
2019-06-04 17:48         ` Joel Fernandes
2019-06-04 14:01   ` Rasmus Villemoes
2019-06-04 23:57     ` Joel Fernandes
2019-06-01 22:27 ` [RFC 2/6] ipv4: add lockdep condition to fix for_each_entry Joel Fernandes (Google)
2019-06-02  7:00   ` Pavel Machek
2019-06-02 12:20     ` Joel Fernandes
2019-06-02 12:24       ` Joel Fernandes
2019-06-03  6:42         ` Pavel Machek
2019-06-03 12:28           ` Joel Fernandes
2019-06-01 22:27 ` [RFC 3/6] driver/core: Convert to use built-in RCU list checking Joel Fernandes (Google)
2019-06-01 22:27 ` [RFC 4/6] workqueue: Convert for_each_wq to use built-in list check Joel Fernandes (Google)
2019-06-05  1:24   ` Daniel Jordan
2019-06-05 13:04     ` Joel Fernandes
2019-06-01 22:27 ` [RFC 5/6] x86/pci: Pass lockdep condition to pcm_mmcfg_list iterator Joel Fernandes (Google)
2019-06-01 22:27 ` [RFC 6/6] acpi: Use built-in RCU list checking for acpi_ioremaps list Joel Fernandes (Google)

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