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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>
This commit is contained in:
Paul E. McKenney
parent
d5988af531
commit
b3fbab0571
@ -548,7 +548,7 @@ do { \
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#endif
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#ifdef CONFIG_PROVE_RCU
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extern void lockdep_rcu_dereference(const char *file, const int line);
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void lockdep_rcu_suspicious(const char *file, const int line, const char *s);
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#endif
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#endif /* __LINUX_LOCKDEP_H */
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@ -297,19 +297,31 @@ extern int rcu_my_thread_group_empty(void);
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/**
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* rcu_lockdep_assert - emit lockdep splat if specified condition not met
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* @c: condition to check
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* @s: informative message
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*/
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#define rcu_lockdep_assert(c) \
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#define rcu_lockdep_assert(c, s) \
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do { \
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static bool __warned; \
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if (debug_lockdep_rcu_enabled() && !__warned && !(c)) { \
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__warned = true; \
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lockdep_rcu_dereference(__FILE__, __LINE__); \
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lockdep_rcu_suspicious(__FILE__, __LINE__, s); \
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} \
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} while (0)
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#define rcu_sleep_check() \
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do { \
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rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map), \
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"Illegal context switch in RCU-bh" \
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" read-side critical section"); \
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rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map), \
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"Illegal context switch in RCU-sched"\
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" read-side critical section"); \
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} while (0)
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#else /* #ifdef CONFIG_PROVE_RCU */
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#define rcu_lockdep_assert(c) do { } while (0)
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#define rcu_lockdep_assert(c, s) do { } while (0)
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#define rcu_sleep_check() do { } while (0)
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#endif /* #else #ifdef CONFIG_PROVE_RCU */
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@ -338,14 +350,16 @@ extern int rcu_my_thread_group_empty(void);
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#define __rcu_dereference_check(p, c, space) \
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({ \
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typeof(*p) *_________p1 = (typeof(*p)*__force )ACCESS_ONCE(p); \
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rcu_lockdep_assert(c); \
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rcu_lockdep_assert(c, "suspicious rcu_dereference_check()" \
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" usage"); \
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rcu_dereference_sparse(p, space); \
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smp_read_barrier_depends(); \
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((typeof(*p) __force __kernel *)(_________p1)); \
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})
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#define __rcu_dereference_protected(p, c, space) \
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({ \
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rcu_lockdep_assert(c); \
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rcu_lockdep_assert(c, "suspicious rcu_dereference_protected()" \
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" usage"); \
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rcu_dereference_sparse(p, space); \
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((typeof(*p) __force __kernel *)(p)); \
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})
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@ -359,7 +373,9 @@ extern int rcu_my_thread_group_empty(void);
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#define __rcu_dereference_index_check(p, c) \
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({ \
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typeof(p) _________p1 = ACCESS_ONCE(p); \
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rcu_lockdep_assert(c); \
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rcu_lockdep_assert(c, \
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"suspicious rcu_dereference_index_check()" \
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" usage"); \
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smp_read_barrier_depends(); \
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(_________p1); \
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})
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@ -1129,10 +1129,11 @@ print_circular_bug_header(struct lock_list *entry, unsigned int depth,
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if (debug_locks_silent)
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return 0;
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printk("\n=======================================================\n");
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printk( "[ INFO: possible circular locking dependency detected ]\n");
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printk("\n");
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printk("======================================================\n");
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printk("[ INFO: possible circular locking dependency detected ]\n");
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print_kernel_version();
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printk( "-------------------------------------------------------\n");
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printk("-------------------------------------------------------\n");
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printk("%s/%d is trying to acquire lock:\n",
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curr->comm, task_pid_nr(curr));
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print_lock(check_src);
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@ -1463,11 +1464,12 @@ print_bad_irq_dependency(struct task_struct *curr,
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if (!debug_locks_off_graph_unlock() || debug_locks_silent)
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return 0;
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printk("\n======================================================\n");
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printk( "[ INFO: %s-safe -> %s-unsafe lock order detected ]\n",
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printk("\n");
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printk("======================================================\n");
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printk("[ INFO: %s-safe -> %s-unsafe lock order detected ]\n",
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irqclass, irqclass);
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print_kernel_version();
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printk( "------------------------------------------------------\n");
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printk("------------------------------------------------------\n");
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printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
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curr->comm, task_pid_nr(curr),
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curr->hardirq_context, hardirq_count() >> HARDIRQ_SHIFT,
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@ -1692,10 +1694,11 @@ print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
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if (!debug_locks_off_graph_unlock() || debug_locks_silent)
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return 0;
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printk("\n=============================================\n");
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printk( "[ INFO: possible recursive locking detected ]\n");
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printk("\n");
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printk("=============================================\n");
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printk("[ INFO: possible recursive locking detected ]\n");
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print_kernel_version();
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printk( "---------------------------------------------\n");
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printk("---------------------------------------------\n");
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printk("%s/%d is trying to acquire lock:\n",
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curr->comm, task_pid_nr(curr));
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print_lock(next);
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@ -2177,10 +2180,11 @@ print_usage_bug(struct task_struct *curr, struct held_lock *this,
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if (!debug_locks_off_graph_unlock() || debug_locks_silent)
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return 0;
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printk("\n=================================\n");
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printk( "[ INFO: inconsistent lock state ]\n");
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printk("\n");
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printk("=================================\n");
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printk("[ INFO: inconsistent lock state ]\n");
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print_kernel_version();
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printk( "---------------------------------\n");
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printk("---------------------------------\n");
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printk("inconsistent {%s} -> {%s} usage.\n",
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usage_str[prev_bit], usage_str[new_bit]);
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@ -2241,10 +2245,11 @@ print_irq_inversion_bug(struct task_struct *curr,
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if (!debug_locks_off_graph_unlock() || debug_locks_silent)
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return 0;
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printk("\n=========================================================\n");
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printk( "[ INFO: possible irq lock inversion dependency detected ]\n");
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printk("\n");
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printk("=========================================================\n");
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printk("[ INFO: possible irq lock inversion dependency detected ]\n");
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print_kernel_version();
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printk( "---------------------------------------------------------\n");
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printk("---------------------------------------------------------\n");
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printk("%s/%d just changed the state of lock:\n",
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curr->comm, task_pid_nr(curr));
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print_lock(this);
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@ -3065,9 +3070,10 @@ print_unlock_inbalance_bug(struct task_struct *curr, struct lockdep_map *lock,
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if (debug_locks_silent)
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return 0;
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printk("\n=====================================\n");
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printk( "[ BUG: bad unlock balance detected! ]\n");
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printk( "-------------------------------------\n");
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printk("\n");
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printk("=====================================\n");
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printk("[ BUG: bad unlock balance detected! ]\n");
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printk("-------------------------------------\n");
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printk("%s/%d is trying to release lock (",
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curr->comm, task_pid_nr(curr));
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print_lockdep_cache(lock);
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@ -3478,9 +3484,10 @@ print_lock_contention_bug(struct task_struct *curr, struct lockdep_map *lock,
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if (debug_locks_silent)
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return 0;
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printk("\n=================================\n");
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printk( "[ BUG: bad contention detected! ]\n");
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printk( "---------------------------------\n");
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printk("\n");
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printk("=================================\n");
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printk("[ BUG: bad contention detected! ]\n");
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printk("---------------------------------\n");
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printk("%s/%d is trying to contend lock (",
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curr->comm, task_pid_nr(curr));
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print_lockdep_cache(lock);
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@ -3839,9 +3846,10 @@ print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
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if (debug_locks_silent)
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return;
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printk("\n=========================\n");
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printk( "[ BUG: held lock freed! ]\n");
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printk( "-------------------------\n");
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printk("\n");
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printk("=========================\n");
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printk("[ BUG: held lock freed! ]\n");
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printk("-------------------------\n");
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printk("%s/%d is freeing memory %p-%p, with a lock still held there!\n",
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curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
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print_lock(hlock);
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@ -3895,9 +3903,10 @@ static void print_held_locks_bug(struct task_struct *curr)
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if (debug_locks_silent)
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return;
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printk("\n=====================================\n");
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printk( "[ BUG: lock held at task exit time! ]\n");
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printk( "-------------------------------------\n");
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printk("\n");
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printk("=====================================\n");
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printk("[ BUG: lock held at task exit time! ]\n");
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printk("-------------------------------------\n");
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printk("%s/%d is exiting with locks still held!\n",
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curr->comm, task_pid_nr(curr));
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lockdep_print_held_locks(curr);
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@ -3991,16 +4000,17 @@ void lockdep_sys_exit(void)
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if (unlikely(curr->lockdep_depth)) {
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if (!debug_locks_off())
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return;
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printk("\n================================================\n");
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printk( "[ BUG: lock held when returning to user space! ]\n");
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printk( "------------------------------------------------\n");
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printk("\n");
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printk("================================================\n");
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printk("[ BUG: lock held when returning to user space! ]\n");
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printk("------------------------------------------------\n");
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printk("%s/%d is leaving the kernel with locks still held!\n",
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curr->comm, curr->pid);
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lockdep_print_held_locks(curr);
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}
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}
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void lockdep_rcu_dereference(const char *file, const int line)
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void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
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{
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struct task_struct *curr = current;
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@ -4009,15 +4019,15 @@ void lockdep_rcu_dereference(const char *file, const int line)
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return;
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#endif /* #ifdef CONFIG_PROVE_RCU_REPEATEDLY */
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/* Note: the following can be executed concurrently, so be careful. */
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printk("\n===================================================\n");
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printk( "[ INFO: suspicious rcu_dereference_check() usage. ]\n");
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printk( "---------------------------------------------------\n");
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printk("%s:%d invoked rcu_dereference_check() without protection!\n",
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file, line);
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printk("\n");
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printk("===============================\n");
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printk("[ INFO: suspicious RCU usage. ]\n");
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printk("-------------------------------\n");
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printk("%s:%d %s!\n", file, line, s);
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printk("\nother info that might help us debug this:\n\n");
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printk("\nrcu_scheduler_active = %d, debug_locks = %d\n", rcu_scheduler_active, debug_locks);
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lockdep_print_held_locks(curr);
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printk("\nstack backtrace:\n");
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dump_stack();
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}
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EXPORT_SYMBOL_GPL(lockdep_rcu_dereference);
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EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious);
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@ -418,7 +418,9 @@ EXPORT_SYMBOL(pid_task);
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*/
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struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns)
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{
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rcu_lockdep_assert(rcu_read_lock_held());
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rcu_lockdep_assert(rcu_read_lock_held(),
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"find_task_by_pid_ns() needs rcu_read_lock()"
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" protection");
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return pid_task(find_pid_ns(nr, ns), PIDTYPE_PID);
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}
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@ -4237,6 +4237,7 @@ static inline void schedule_debug(struct task_struct *prev)
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*/
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if (unlikely(in_atomic_preempt_off() && !prev->exit_state))
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__schedule_bug(prev);
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rcu_sleep_check();
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profile_hit(SCHED_PROFILING, __builtin_return_address(0));
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@ -8230,6 +8231,7 @@ void __might_sleep(const char *file, int line, int preempt_offset)
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{
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static unsigned long prev_jiffy; /* ratelimiting */
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rcu_sleep_check(); /* WARN_ON_ONCE() by default, no rate limit reqd. */
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if ((preempt_count_equals(preempt_offset) && !irqs_disabled()) ||
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system_state != SYSTEM_RUNNING || oops_in_progress)
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return;
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