mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-26 02:39:48 +00:00
![Mathieu Desnoyers](/assets/img/avatar_default.png)
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>
276 lines
7.8 KiB
C
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 */
|