From: Joel Fernandes <joel@joelfernandes.org>
To: "Paul E. McKenney" <paulmck@linux.ibm.com>
Cc: linux-kernel@vger.kernel.org,
Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
Bjorn Helgaas <bhelgaas@google.com>,
Borislav Petkov <bp@alien8.de>,
c0d1n61at3@gmail.com, "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>,
Jonathan Corbet <corbet@lwn.net>,
Josh Triplett <josh@joshtriplett.org>,
keescook@chromium.org, kernel-hardening@lists.openwall.com,
kernel-team@android.com, Lai Jiangshan <jiangshanlai@gmail.com>,
Len Brown <lenb@kernel.org>,
linux-acpi@vger.kernel.org, linux-doc@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 Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
peterz@infradead.org, "Rafael J. Wysocki" <rjw@rjwysocki.net>,
Rasmus Villemoes <rasmus.villemoes@prevas.dk>,
rcu@vger.kernel.org, Steven Rostedt <rostedt@goodmis.org>,
Tejun Heo <tj@kernel.org>, Thomas Gleixner <tglx@linutronix.de>,
will@kernel.org,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<x86@kernel.org>
Subject: Re: [PATCH 2/9] rcu: Add support for consolidated-RCU reader checking (v3)
Date: Tue, 16 Jul 2019 14:46:49 -0400 [thread overview]
Message-ID: <20190716184649.GA130463@google.com> (raw)
In-Reply-To: <20190716183833.GD14271@linux.ibm.com>
On Tue, Jul 16, 2019 at 11:38:33AM -0700, Paul E. McKenney wrote:
> On Mon, Jul 15, 2019 at 10:36:58AM -0400, Joel Fernandes (Google) wrote:
> > This patch adds support for checking RCU reader sections in list
> > traversal macros. Optionally, if the list macro is called under SRCU or
> > other lock/mutex protection, then appropriate lockdep expressions can be
> > passed to make the checks pass.
> >
> > Existing list_for_each_entry_rcu() invocations don't need to pass the
> > optional fourth argument (cond) unless they are under some non-RCU
> > protection and needs to make lockdep check pass.
> >
> > Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
>
> Now that I am on the correct version, again please fold in the checks
> for the extra argument. The ability to have an optional argument looks
> quite helpful, especially when compared to growing the RCU API!
I did fold this and replied with a pull request URL based on /dev branch. But
we can hold off on the pull requests until we decide on the below comments:
> 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.
But I don't mind dropping it and it may just accelerate the fixing up of all
callers.
> > +#define __list_check_rcu(dummy, cond, ...) \
> > + ({ \
> > + RCU_LOCKDEP_WARN(!cond && !rcu_read_lock_any_held(), \
> > + "RCU-list traversed in non-reader section!"); \
> > + })
> > +#else
> > +#define __list_check_rcu(dummy, cond, ...) ({})
> > +#endif
> > +
> > /*
> > * Insert a new entry between two known consecutive entries.
> > *
> > @@ -343,14 +357,16 @@ static inline void list_splice_tail_init_rcu(struct list_head *list,
> > * @pos: the type * to use as a loop cursor.
> > * @head: the head for your list.
> > * @member: the name of the list_head within the struct.
> > + * @cond: optional lockdep expression if called from non-RCU protection.
> > *
> > * This list-traversal primitive may safely run concurrently with
> > * the _rcu list-mutation primitives such as list_add_rcu()
> > * as long as the traversal is guarded by rcu_read_lock().
> > */
> > -#define list_for_each_entry_rcu(pos, head, member) \
> > - for (pos = list_entry_rcu((head)->next, typeof(*pos), member); \
> > - &pos->member != (head); \
> > +#define list_for_each_entry_rcu(pos, head, member, cond...) \
> > + for (__list_check_rcu(dummy, ## cond, 0), \
> > + pos = list_entry_rcu((head)->next, typeof(*pos), member); \
> > + &pos->member != (head); \
> > pos = list_entry_rcu(pos->member.next, typeof(*pos), member))
> >
> > /**
> > @@ -616,13 +632,15 @@ static inline void hlist_add_behind_rcu(struct hlist_node *n,
> > * @pos: the type * to use as a loop cursor.
> > * @head: the head for your list.
> > * @member: the name of the hlist_node within the struct.
> > + * @cond: optional lockdep expression if called from non-RCU protection.
> > *
> > * This list-traversal primitive may safely run concurrently with
> > * 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) \
> > - for (pos = hlist_entry_safe (rcu_dereference_raw(hlist_first_rcu(head)),\
> > +#define hlist_for_each_entry_rcu(pos, head, member, cond...) \
> > + for (__list_check_rcu(dummy, ## cond, 0), \
> > + 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(\
> > diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> > index 8f7167478c1d..f3c29efdf19a 100644
> > --- a/include/linux/rcupdate.h
> > +++ b/include/linux/rcupdate.h
> > @@ -221,6 +221,7 @@ int debug_lockdep_rcu_enabled(void);
> > int rcu_read_lock_held(void);
> > int rcu_read_lock_bh_held(void);
> > int rcu_read_lock_sched_held(void);
> > +int rcu_read_lock_any_held(void);
> >
> > #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
> >
> > @@ -241,6 +242,12 @@ static inline int rcu_read_lock_sched_held(void)
> > {
> > return !preemptible();
> > }
> > +
> > +static inline int rcu_read_lock_any_held(void)
> > +{
> > + return !preemptible();
> > +}
> > +
> > #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
> >
> > #ifdef CONFIG_PROVE_RCU
> > diff --git a/kernel/rcu/Kconfig.debug b/kernel/rcu/Kconfig.debug
> > index 5ec3ea4028e2..7fbd21dbfcd0 100644
> > --- a/kernel/rcu/Kconfig.debug
> > +++ b/kernel/rcu/Kconfig.debug
> > @@ -8,6 +8,17 @@ menu "RCU Debugging"
> > config PROVE_RCU
> > def_bool PROVE_LOCKING
> >
> > +config PROVE_RCU_LIST
> > + bool "RCU list lockdep debugging"
> > + depends on PROVE_RCU
>
> This must also depend on RCU_EXPERT.
Sure.
> > + default n
> > + help
> > + Enable RCU lockdep checking for list usages. By default it is
> > + turned off since there are several list RCU users that still
> > + need to be converted to pass a lockdep expression. To prevent
> > + false-positive splats, we keep it default disabled but once all
> > + users are converted, we can remove this config option.
> > +
> > config TORTURE_TEST
> > tristate
> > default n
> > diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
> > index 9dd5aeef6e70..b7a4e3b5fa98 100644
> > --- a/kernel/rcu/update.c
> > +++ b/kernel/rcu/update.c
> > @@ -91,14 +91,18 @@ module_param(rcu_normal_after_boot, int, 0);
> > * Similarly, we avoid claiming an SRCU read lock held if the current
> > * CPU is offline.
> > */
> > +#define rcu_read_lock_held_common() \
> > + if (!debug_lockdep_rcu_enabled()) \
> > + return 1; \
> > + if (!rcu_is_watching()) \
> > + return 0; \
> > + if (!rcu_lockdep_current_cpu_online()) \
> > + return 0;
>
> Nice abstraction of common code!
Thanks!
next prev parent reply other threads:[~2019-07-16 18:47 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-15 14:36 [PATCH 0/9] Harden list_for_each_entry_rcu() and family Joel Fernandes (Google)
2019-07-15 14:36 ` [PATCH 1/9] rcu/update: Remove useless check for debug_locks (v1) Joel Fernandes (Google)
2019-07-15 14:36 ` [PATCH 2/9] rcu: Add support for consolidated-RCU reader checking (v3) Joel Fernandes (Google)
2019-07-16 18:38 ` Paul E. McKenney
2019-07-16 18:46 ` Joel Fernandes [this message]
2019-07-16 18:53 ` Paul E. McKenney
2019-07-16 22:02 ` Joel Fernandes
2019-07-17 0:07 ` Paul E. McKenney
2019-07-15 14:36 ` [PATCH 3/9] rcu/sync: Remove custom check for reader-section (v2) Joel Fernandes (Google)
2019-07-16 18:39 ` Paul E. McKenney
2019-07-15 14:37 ` [PATCH 4/9] ipv4: add lockdep condition to fix for_each_entry (v1) Joel Fernandes (Google)
2019-07-16 18:39 ` Paul E. McKenney
2019-07-16 21:12 ` David Miller
2019-07-15 14:37 ` [PATCH 5/9] driver/core: Convert to use built-in RCU list checking (v1) Joel Fernandes (Google)
2019-07-16 18:40 ` Paul E. McKenney
2019-07-15 14:37 ` [PATCH 6/9] workqueue: Convert for_each_wq to use built-in list check (v2) Joel Fernandes (Google)
2019-07-16 18:41 ` Paul E. McKenney
2019-07-15 14:37 ` [PATCH 7/9] x86/pci: Pass lockdep condition to pcm_mmcfg_list iterator (v1) Joel Fernandes (Google)
2019-07-15 20:02 ` Bjorn Helgaas
2019-07-16 4:03 ` Joel Fernandes
2019-07-16 18:42 ` Paul E. McKenney
2019-07-15 14:37 ` [PATCH 8/9] acpi: Use built-in RCU list checking for acpi_ioremaps list (v1) Joel Fernandes (Google)
2019-07-15 21:44 ` Rafael J. Wysocki
2019-07-16 18:43 ` Paul E. McKenney
2019-07-15 14:37 ` [PATCH 9/9] doc: Update documentation about list_for_each_entry_rcu (v1) Joel Fernandes (Google)
2019-07-16 18:46 ` [PATCH 0/9] Harden list_for_each_entry_rcu() and family Paul E. McKenney
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