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rcu: Restore checks for blocking in RCU read-side critical sections

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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>
This commit is contained in:
Paul E. McKenney
2011-05-24 08:31:09 -07:00
parent d5988af531
commit b3fbab0571
5 changed files with 75 additions and 45 deletions
Download Patch File Download Diff File Expand all files Collapse all files

84
kernel/lockdep.c
View File

@ -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);