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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2011-05-24 08:31:09 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2011-09-28 21:36:37 -0700
commitb3fbab0571eb09746cc0283648165ec00efc8eb2 (patch)
tree63bc01cbf03a5df34a96af292a00df4a96dc148a /kernel
parentd5988af53102f3b73e5e0788be024ccfa51869de (diff)
rcu: Restore checks for blocking in RCU read-side critical sections
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. Also, 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. Finally, fix some checkpatch whitespace complaints in lockdep.c. 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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/lockdep.c84
-rw-r--r--kernel/pid.c4
-rw-r--r--kernel/sched.c2
3 files changed, 52 insertions, 38 deletions
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 91d67ce3a8d5..1e48f1c3ea70 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -1129,10 +1129,11 @@ 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);
@@ -1463,11 +1464,12 @@ 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,
@@ -1692,10 +1694,11 @@ 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);
@@ -2177,10 +2180,11 @@ 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]);
@@ -2241,10 +2245,11 @@ 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);
@@ -3065,9 +3070,10 @@ 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);
@@ -3478,9 +3484,10 @@ 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);
@@ -3839,9 +3846,10 @@ 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);
@@ -3895,9 +3903,10 @@ 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);
@@ -3991,16 +4000,17 @@ 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;
@@ -4009,15 +4019,15 @@ 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 e432057f3b21..8cafe7e72ad2 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -418,7 +418,9 @@ 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 ec5f472bc5b9..e24cebe0e6cb 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4237,6 +4237,7 @@ 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));
@@ -8230,6 +8231,7 @@ void __might_sleep(const char *file, int line, int preempt_offset)
{
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;