lkml.org 
[lkml]   [2011]   [Jun]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH tip/core/rcu 04/28] rcu: Restore checks for blocking in RCU read-side critical sections
Date
Long ago, using TREE_RCU with PREEMPT would result in "scheduling
while atomic" diagnostics if you blocked in an RCU read-side critical
section. However, PREEMPT now implies TREE_PREEMPT_RCU, which defeats
this diagnostic. This commit therefore adds a replacement diagnostic
based on PROVE_RCU.

Because rcu_lockdep_assert() and lockdep_rcu_dereference() are now being
used for things that have nothing to do with rcu_dereference(), rename
lockdep_rcu_dereference() to lockdep_rcu_suspicious() and add a third
argument that is a string indicating what is suspicious. This third
argument is passed in from a new third argument to rcu_lockdep_assert().
Update all calls to rcu_lockdep_assert() to add an informative third
argument.

Finally, add a pair of rcu_lockdep_assert() calls from within
rcu_note_context_switch(), one complaining if a context switch occurs
in an RCU-bh read-side critical section and another complaining if a
context switch occurs in an RCU-sched read-side critical section.
These are present only if the PROVE_RCU kernel parameter is enabled.

Again, you must enable PROVE_RCU to see these new diagnostics. But you
are enabling PROVE_RCU to check out new RCU uses in any case, aren't you?

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
include/linux/lockdep.h | 2 +-
include/linux/rcupdate.h | 28 ++++++++++++---
kernel/lockdep.c | 84 +++++++++++++++++++++++++--------------------
kernel/pid.c | 4 ++-
kernel/sched.c | 2 +
5 files changed, 75 insertions(+), 45 deletions(-)
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 4aef1dd..bfa66e7 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -545,7 +545,7 @@ do { \
#endif

#ifdef CONFIG_PROVE_RCU
-extern void lockdep_rcu_dereference(const char *file, const int line);
+void lockdep_rcu_suspicious(const char *file, const int line, const char *s);
#endif

#endif /* __LINUX_LOCKDEP_H */
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 99f9aa7..8be0433 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -297,19 +297,31 @@ extern int rcu_my_thread_group_empty(void);
/**
* rcu_lockdep_assert - emit lockdep splat if specified condition not met
* @c: condition to check
+ * @s: informative message
*/
-#define rcu_lockdep_assert(c) \
+#define rcu_lockdep_assert(c, s) \
do { \
static bool __warned; \
if (debug_lockdep_rcu_enabled() && !__warned && !(c)) { \
__warned = true; \
- lockdep_rcu_dereference(__FILE__, __LINE__); \
+ lockdep_rcu_suspicious(__FILE__, __LINE__, s); \
} \
} while (0)

+#define rcu_sleep_check() \
+ do { \
+ rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map), \
+ "Illegal context switch in RCU-bh" \
+ " read-side critical section"); \
+ rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map), \
+ "Illegal context switch in RCU-sched"\
+ " read-side critical section"); \
+ } while (0)
+
#else /* #ifdef CONFIG_PROVE_RCU */

-#define rcu_lockdep_assert(c) do { } while (0)
+#define rcu_lockdep_assert(c, s) do { } while (0)
+#define rcu_sleep_check() do { } while (0)

#endif /* #else #ifdef CONFIG_PROVE_RCU */

@@ -338,14 +350,16 @@ extern int rcu_my_thread_group_empty(void);
#define __rcu_dereference_check(p, c, space) \
({ \
typeof(*p) *_________p1 = (typeof(*p)*__force )ACCESS_ONCE(p); \
- rcu_lockdep_assert(c); \
+ rcu_lockdep_assert(c, "suspicious rcu_dereference_check()" \
+ " usage"); \
rcu_dereference_sparse(p, space); \
smp_read_barrier_depends(); \
((typeof(*p) __force __kernel *)(_________p1)); \
})
#define __rcu_dereference_protected(p, c, space) \
({ \
- rcu_lockdep_assert(c); \
+ rcu_lockdep_assert(c, "suspicious rcu_dereference_protected()" \
+ " usage"); \
rcu_dereference_sparse(p, space); \
((typeof(*p) __force __kernel *)(p)); \
})
@@ -359,7 +373,9 @@ extern int rcu_my_thread_group_empty(void);
#define __rcu_dereference_index_check(p, c) \
({ \
typeof(p) _________p1 = ACCESS_ONCE(p); \
- rcu_lockdep_assert(c); \
+ rcu_lockdep_assert(c, \
+ "suspicious rcu_dereference_index_check()" \
+ " usage"); \
smp_read_barrier_depends(); \
(_________p1); \
})
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 53a6895..dbf453d 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -1067,10 +1067,11 @@ print_circular_bug_header(struct lock_list *entry, unsigned int depth,
if (debug_locks_silent)
return 0;

- printk("\n=======================================================\n");
- printk( "[ INFO: possible circular locking dependency detected ]\n");
+ printk("\n");
+ printk("======================================================\n");
+ printk("[ INFO: possible circular locking dependency detected ]\n");
print_kernel_version();
- printk( "-------------------------------------------------------\n");
+ printk("-------------------------------------------------------\n");
printk("%s/%d is trying to acquire lock:\n",
curr->comm, task_pid_nr(curr));
print_lock(check_src);
@@ -1340,11 +1341,12 @@ print_bad_irq_dependency(struct task_struct *curr,
if (!debug_locks_off_graph_unlock() || debug_locks_silent)
return 0;

- printk("\n======================================================\n");
- printk( "[ INFO: %s-safe -> %s-unsafe lock order detected ]\n",
+ printk("\n");
+ printk("======================================================\n");
+ printk("[ INFO: %s-safe -> %s-unsafe lock order detected ]\n",
irqclass, irqclass);
print_kernel_version();
- printk( "------------------------------------------------------\n");
+ printk("------------------------------------------------------\n");
printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
curr->comm, task_pid_nr(curr),
curr->hardirq_context, hardirq_count() >> HARDIRQ_SHIFT,
@@ -1546,10 +1548,11 @@ print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
if (!debug_locks_off_graph_unlock() || debug_locks_silent)
return 0;

- printk("\n=============================================\n");
- printk( "[ INFO: possible recursive locking detected ]\n");
+ printk("\n");
+ printk("=============================================\n");
+ printk("[ INFO: possible recursive locking detected ]\n");
print_kernel_version();
- printk( "---------------------------------------------\n");
+ printk("---------------------------------------------\n");
printk("%s/%d is trying to acquire lock:\n",
curr->comm, task_pid_nr(curr));
print_lock(next);
@@ -2018,10 +2021,11 @@ print_usage_bug(struct task_struct *curr, struct held_lock *this,
if (!debug_locks_off_graph_unlock() || debug_locks_silent)
return 0;

- printk("\n=================================\n");
- printk( "[ INFO: inconsistent lock state ]\n");
+ printk("\n");
+ printk("=================================\n");
+ printk("[ INFO: inconsistent lock state ]\n");
print_kernel_version();
- printk( "---------------------------------\n");
+ printk("---------------------------------\n");

printk("inconsistent {%s} -> {%s} usage.\n",
usage_str[prev_bit], usage_str[new_bit]);
@@ -2076,10 +2080,11 @@ print_irq_inversion_bug(struct task_struct *curr,
if (!debug_locks_off_graph_unlock() || debug_locks_silent)
return 0;

- printk("\n=========================================================\n");
- printk( "[ INFO: possible irq lock inversion dependency detected ]\n");
+ printk("\n");
+ printk("=========================================================\n");
+ printk("[ INFO: possible irq lock inversion dependency detected ]\n");
print_kernel_version();
- printk( "---------------------------------------------------------\n");
+ printk("---------------------------------------------------------\n");
printk("%s/%d just changed the state of lock:\n",
curr->comm, task_pid_nr(curr));
print_lock(this);
@@ -2869,9 +2874,10 @@ print_unlock_inbalance_bug(struct task_struct *curr, struct lockdep_map *lock,
if (debug_locks_silent)
return 0;

- printk("\n=====================================\n");
- printk( "[ BUG: bad unlock balance detected! ]\n");
- printk( "-------------------------------------\n");
+ printk("\n");
+ printk("=====================================\n");
+ printk("[ BUG: bad unlock balance detected! ]\n");
+ printk("-------------------------------------\n");
printk("%s/%d is trying to release lock (",
curr->comm, task_pid_nr(curr));
print_lockdep_cache(lock);
@@ -3276,9 +3282,10 @@ print_lock_contention_bug(struct task_struct *curr, struct lockdep_map *lock,
if (debug_locks_silent)
return 0;

- printk("\n=================================\n");
- printk( "[ BUG: bad contention detected! ]\n");
- printk( "---------------------------------\n");
+ printk("\n");
+ printk("=================================\n");
+ printk("[ BUG: bad contention detected! ]\n");
+ printk("---------------------------------\n");
printk("%s/%d is trying to contend lock (",
curr->comm, task_pid_nr(curr));
print_lockdep_cache(lock);
@@ -3637,9 +3644,10 @@ print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
if (debug_locks_silent)
return;

- printk("\n=========================\n");
- printk( "[ BUG: held lock freed! ]\n");
- printk( "-------------------------\n");
+ printk("\n");
+ printk("=========================\n");
+ printk("[ BUG: held lock freed! ]\n");
+ printk("-------------------------\n");
printk("%s/%d is freeing memory %p-%p, with a lock still held there!\n",
curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
print_lock(hlock);
@@ -3693,9 +3701,10 @@ static void print_held_locks_bug(struct task_struct *curr)
if (debug_locks_silent)
return;

- printk("\n=====================================\n");
- printk( "[ BUG: lock held at task exit time! ]\n");
- printk( "-------------------------------------\n");
+ printk("\n");
+ printk("=====================================\n");
+ printk("[ BUG: lock held at task exit time! ]\n");
+ printk("-------------------------------------\n");
printk("%s/%d is exiting with locks still held!\n",
curr->comm, task_pid_nr(curr));
lockdep_print_held_locks(curr);
@@ -3789,16 +3798,17 @@ void lockdep_sys_exit(void)
if (unlikely(curr->lockdep_depth)) {
if (!debug_locks_off())
return;
- printk("\n================================================\n");
- printk( "[ BUG: lock held when returning to user space! ]\n");
- printk( "------------------------------------------------\n");
+ printk("\n");
+ printk("================================================\n");
+ printk("[ BUG: lock held when returning to user space! ]\n");
+ printk("------------------------------------------------\n");
printk("%s/%d is leaving the kernel with locks still held!\n",
curr->comm, curr->pid);
lockdep_print_held_locks(curr);
}
}

-void lockdep_rcu_dereference(const char *file, const int line)
+void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
{
struct task_struct *curr = current;

@@ -3807,15 +3817,15 @@ void lockdep_rcu_dereference(const char *file, const int line)
return;
#endif /* #ifdef CONFIG_PROVE_RCU_REPEATEDLY */
/* Note: the following can be executed concurrently, so be careful. */
- printk("\n===================================================\n");
- printk( "[ INFO: suspicious rcu_dereference_check() usage. ]\n");
- printk( "---------------------------------------------------\n");
- printk("%s:%d invoked rcu_dereference_check() without protection!\n",
- file, line);
+ printk("\n");
+ printk("===============================\n");
+ printk("[ INFO: suspicious RCU usage. ]\n");
+ printk("-------------------------------\n");
+ printk("%s:%d %s!\n", file, line, s);
printk("\nother info that might help us debug this:\n\n");
printk("\nrcu_scheduler_active = %d, debug_locks = %d\n", rcu_scheduler_active, debug_locks);
lockdep_print_held_locks(curr);
printk("\nstack backtrace:\n");
dump_stack();
}
-EXPORT_SYMBOL_GPL(lockdep_rcu_dereference);
+EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious);
diff --git a/kernel/pid.c b/kernel/pid.c
index 57a8346..a7577b3 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -419,7 +419,9 @@ EXPORT_SYMBOL(pid_task);
*/
struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns)
{
- rcu_lockdep_assert(rcu_read_lock_held());
+ rcu_lockdep_assert(rcu_read_lock_held(),
+ "find_task_by_pid_ns() needs rcu_read_lock()"
+ " protection");
return pid_task(find_pid_ns(nr, ns), PIDTYPE_PID);
}

diff --git a/kernel/sched.c b/kernel/sched.c
index 312f8b9..1352dbb 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4021,6 +4021,7 @@ static inline void schedule_debug(struct task_struct *prev)
*/
if (unlikely(in_atomic_preempt_off() && !prev->exit_state))
__schedule_bug(prev);
+ rcu_sleep_check();

profile_hit(SCHED_PROFILING, __builtin_return_address(0));

@@ -8309,6 +8310,7 @@ void __might_sleep(const char *file, int line, int preempt_offset)
#ifdef in_atomic
static unsigned long prev_jiffy; /* ratelimiting */

+ rcu_sleep_check(); /* WARN_ON_ONCE() by default, no rate limit reqd. */
if ((preempt_count_equals(preempt_offset) && !irqs_disabled()) ||
system_state != SYSTEM_RUNNING || oops_in_progress)
return;
--
1.7.3.2


\
 
 \ /
  Last update: 2011-06-08 21:39    [from the cache]
©2003-2011 Jasper Spaans