linux/kernel/rcupdate.c
Mathieu Desnoyers 551d55a944 tree/tiny rcu: Add debug RCU head objects
Helps finding racy users of call_rcu(), which results in hangs because list
entries are overwritten and/or skipped.

Changelog since v4:
- Bissectability is now OK
- Now generate a WARN_ON_ONCE() for non-initialized rcu_head passed to
  call_rcu(). Statically initialized objects are detected with
  object_is_static().
- Rename rcu_head_init_on_stack to init_rcu_head_on_stack.
- Remove init_rcu_head() completely.

Changelog since v3:
- Include comments from Lai Jiangshan

This new patch version is based on the debugobjects with the newly introduced
"active state" tracker.

Non-initialized entries are all considered as "statically initialized". An
activation fixup (triggered by call_rcu()) takes care of performing the debug
object initialization without issuing any warning. Since we cannot increase the
size of struct rcu_head, I don't see much room to put an identifier for
statically initialized rcu_head structures. So for now, we have to live without
"activation without explicit init" detection. But the main purpose of this debug
option is to detect double-activations (double call_rcu() use of a rcu_head
before the callback is executed), which is correctly addressed here.

This also detects potential internal RCU callback corruption, which would cause
the callbacks to be executed twice.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
CC: David S. Miller <davem@davemloft.net>
CC: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
CC: akpm@linux-foundation.org
CC: mingo@elte.hu
CC: laijs@cn.fujitsu.com
CC: dipankar@in.ibm.com
CC: josh@joshtriplett.org
CC: dvhltc@us.ibm.com
CC: niv@us.ibm.com
CC: tglx@linutronix.de
CC: peterz@infradead.org
CC: rostedt@goodmis.org
CC: Valdis.Kletnieks@vt.edu
CC: dhowells@redhat.com
CC: eric.dumazet@gmail.com
CC: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
2010-06-14 16:37:26 -07:00

276 lines
7.8 KiB
C

/*
* Read-Copy Update mechanism for mutual exclusion
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Copyright IBM Corporation, 2001
*
* Authors: Dipankar Sarma <dipankar@in.ibm.com>
* Manfred Spraul <manfred@colorfullife.com>
*
* Based on the original work by Paul McKenney <paulmck@us.ibm.com>
* and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
* Papers:
* http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf
* http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001)
*
* For detailed explanation of Read-Copy Update mechanism see -
* http://lse.sourceforge.net/locking/rcupdate.html
*
*/
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/smp.h>
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <asm/atomic.h>
#include <linux/bitops.h>
#include <linux/percpu.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/mutex.h>
#include <linux/module.h>
#include <linux/hardirq.h>
#ifdef CONFIG_DEBUG_LOCK_ALLOC
static struct lock_class_key rcu_lock_key;
struct lockdep_map rcu_lock_map =
STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key);
EXPORT_SYMBOL_GPL(rcu_lock_map);
static struct lock_class_key rcu_bh_lock_key;
struct lockdep_map rcu_bh_lock_map =
STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_bh", &rcu_bh_lock_key);
EXPORT_SYMBOL_GPL(rcu_bh_lock_map);
static struct lock_class_key rcu_sched_lock_key;
struct lockdep_map rcu_sched_lock_map =
STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key);
EXPORT_SYMBOL_GPL(rcu_sched_lock_map);
#endif
#ifdef CONFIG_DEBUG_LOCK_ALLOC
int debug_lockdep_rcu_enabled(void)
{
return rcu_scheduler_active && debug_locks &&
current->lockdep_recursion == 0;
}
EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled);
/**
* rcu_read_lock_bh_held - might we be in RCU-bh read-side critical section?
*
* Check for bottom half being disabled, which covers both the
* CONFIG_PROVE_RCU and not cases. Note that if someone uses
* rcu_read_lock_bh(), but then later enables BH, lockdep (if enabled)
* will show the situation.
*
* Check debug_lockdep_rcu_enabled() to prevent false positives during boot.
*/
int rcu_read_lock_bh_held(void)
{
if (!debug_lockdep_rcu_enabled())
return 1;
return in_softirq();
}
EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);
#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
/*
* Awaken the corresponding synchronize_rcu() instance now that a
* grace period has elapsed.
*/
void wakeme_after_rcu(struct rcu_head *head)
{
struct rcu_synchronize *rcu;
rcu = container_of(head, struct rcu_synchronize, head);
complete(&rcu->completion);
}
#ifdef CONFIG_PROVE_RCU
/*
* wrapper function to avoid #include problems.
*/
int rcu_my_thread_group_empty(void)
{
return thread_group_empty(current);
}
EXPORT_SYMBOL_GPL(rcu_my_thread_group_empty);
#endif /* #ifdef CONFIG_PROVE_RCU */
#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
static inline void debug_init_rcu_head(struct rcu_head *head)
{
debug_object_init(head, &rcuhead_debug_descr);
}
static inline void debug_rcu_head_free(struct rcu_head *head)
{
debug_object_free(head, &rcuhead_debug_descr);
}
/*
* fixup_init is called when:
* - an active object is initialized
*/
static int rcuhead_fixup_init(void *addr, enum debug_obj_state state)
{
struct rcu_head *head = addr;
switch (state) {
case ODEBUG_STATE_ACTIVE:
/*
* Ensure that queued callbacks are all executed.
* If we detect that we are nested in a RCU read-side critical
* section, we should simply fail, otherwise we would deadlock.
*/
if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
irqs_disabled()) {
WARN_ON(1);
return 0;
}
rcu_barrier();
rcu_barrier_sched();
rcu_barrier_bh();
debug_object_init(head, &rcuhead_debug_descr);
return 1;
default:
return 0;
}
}
/*
* fixup_activate is called when:
* - an active object is activated
* - an unknown object is activated (might be a statically initialized object)
* Activation is performed internally by call_rcu().
*/
static int rcuhead_fixup_activate(void *addr, enum debug_obj_state state)
{
struct rcu_head *head = addr;
switch (state) {
case ODEBUG_STATE_NOTAVAILABLE:
/*
* This is not really a fixup. We just make sure that it is
* tracked in the object tracker.
*/
debug_object_init(head, &rcuhead_debug_descr);
debug_object_activate(head, &rcuhead_debug_descr);
return 0;
case ODEBUG_STATE_ACTIVE:
/*
* Ensure that queued callbacks are all executed.
* If we detect that we are nested in a RCU read-side critical
* section, we should simply fail, otherwise we would deadlock.
*/
if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
irqs_disabled()) {
WARN_ON(1);
return 0;
}
rcu_barrier();
rcu_barrier_sched();
rcu_barrier_bh();
debug_object_activate(head, &rcuhead_debug_descr);
return 1;
default:
return 0;
}
}
/*
* fixup_free is called when:
* - an active object is freed
*/
static int rcuhead_fixup_free(void *addr, enum debug_obj_state state)
{
struct rcu_head *head = addr;
switch (state) {
case ODEBUG_STATE_ACTIVE:
/*
* Ensure that queued callbacks are all executed.
* If we detect that we are nested in a RCU read-side critical
* section, we should simply fail, otherwise we would deadlock.
*/
#ifndef CONFIG_PREEMPT
WARN_ON(1);
return 0;
#else
if (rcu_preempt_depth() != 0 || preempt_count() != 0 ||
irqs_disabled()) {
WARN_ON(1);
return 0;
}
rcu_barrier();
rcu_barrier_sched();
rcu_barrier_bh();
debug_object_free(head, &rcuhead_debug_descr);
return 1;
#endif
default:
return 0;
}
}
/**
* init_rcu_head_on_stack() - initialize on-stack rcu_head for debugobjects
* @head: pointer to rcu_head structure to be initialized
*
* This function informs debugobjects of a new rcu_head structure that
* has been allocated as an auto variable on the stack. This function
* is not required for rcu_head structures that are statically defined or
* that are dynamically allocated on the heap. This function has no
* effect for !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
*/
void init_rcu_head_on_stack(struct rcu_head *head)
{
debug_object_init_on_stack(head, &rcuhead_debug_descr);
}
EXPORT_SYMBOL_GPL(init_rcu_head_on_stack);
/**
* destroy_rcu_head_on_stack() - destroy on-stack rcu_head for debugobjects
* @head: pointer to rcu_head structure to be initialized
*
* This function informs debugobjects that an on-stack rcu_head structure
* is about to go out of scope. As with init_rcu_head_on_stack(), this
* function is not required for rcu_head structures that are statically
* defined or that are dynamically allocated on the heap. Also as with
* init_rcu_head_on_stack(), this function has no effect for
* !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel builds.
*/
void destroy_rcu_head_on_stack(struct rcu_head *head)
{
debug_object_free(head, &rcuhead_debug_descr);
}
EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack);
struct debug_obj_descr rcuhead_debug_descr = {
.name = "rcu_head",
.fixup_init = rcuhead_fixup_init,
.fixup_activate = rcuhead_fixup_activate,
.fixup_free = rcuhead_fixup_free,
};
EXPORT_SYMBOL_GPL(rcuhead_debug_descr);
#endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */