From b3fbab0571eb09746cc0283648165ec00efc8eb2 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 24 May 2011 08:31:09 -0700 Subject: 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 --- kernel/lockdep.c | 84 +++++++++++++++++++++++++++++++------------------------- 1 file changed, 47 insertions(+), 37 deletions(-) (limited to 'kernel/lockdep.c') 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); -- cgit v1.2.1