#include <linux/compiler.h>
+ /**
+ * DOC: scope-based cleanup helpers
+ *
+ * The "goto error" pattern is notorious for introducing subtle resource
+ * leaks. It is tedious and error prone to add new resource acquisition
+ * constraints into code paths that already have several unwind
+ * conditions. The "cleanup" helpers enable the compiler to help with
+ * this tedium and can aid in maintaining LIFO (last in first out)
+ * unwind ordering to avoid unintentional leaks.
+ *
+ * As drivers make up the majority of the kernel code base, here is an
+ * example of using these helpers to clean up PCI drivers. The target of
+ * the cleanups are occasions where a goto is used to unwind a device
+ * reference (pci_dev_put()), or unlock the device (pci_dev_unlock())
+ * before returning.
+ *
+ * The DEFINE_FREE() macro can arrange for PCI device references to be
+ * dropped when the associated variable goes out of scope::
+ *
+ * DEFINE_FREE(pci_dev_put, struct pci_dev *, if (_T) pci_dev_put(_T))
+ * ...
+ * struct pci_dev *dev __free(pci_dev_put) =
+ * pci_get_slot(parent, PCI_DEVFN(0, 0));
+ *
+ * The above will automatically call pci_dev_put() if @dev is non-NULL
+ * when @dev goes out of scope (automatic variable scope). If a function
+ * wants to invoke pci_dev_put() on error, but return @dev (i.e. without
+ * freeing it) on success, it can do::
+ *
+ * return no_free_ptr(dev);
+ *
+ * ...or::
+ *
+ * return_ptr(dev);
+ *
+ * The DEFINE_GUARD() macro can arrange for the PCI device lock to be
+ * dropped when the scope where guard() is invoked ends::
+ *
+ * DEFINE_GUARD(pci_dev, struct pci_dev *, pci_dev_lock(_T), pci_dev_unlock(_T))
+ * ...
+ * guard(pci_dev)(dev);
+ *
+ * The lifetime of the lock obtained by the guard() helper follows the
+ * scope of automatic variable declaration. Take the following example::
+ *
+ * func(...)
+ * {
+ * if (...) {
+ * ...
+ * guard(pci_dev)(dev); // pci_dev_lock() invoked here
+ * ...
+ * } // <- implied pci_dev_unlock() triggered here
+ * }
+ *
+ * Observe the lock is held for the remainder of the "if ()" block not
+ * the remainder of "func()".
+ *
+ * Now, when a function uses both __free() and guard(), or multiple
+ * instances of __free(), the LIFO order of variable definition order
+ * matters. GCC documentation says:
+ *
+ * "When multiple variables in the same scope have cleanup attributes,
+ * at exit from the scope their associated cleanup functions are run in
+ * reverse order of definition (last defined, first cleanup)."
+ *
+ * When the unwind order matters it requires that variables be defined
+ * mid-function scope rather than at the top of the file. Take the
+ * following example and notice the bug highlighted by "!!"::
+ *
+ * LIST_HEAD(list);
+ * DEFINE_MUTEX(lock);
+ *
+ * struct object {
+ * struct list_head node;
+ * };
+ *
+ * static struct object *alloc_add(void)
+ * {
+ * struct object *obj;
+ *
+ * lockdep_assert_held(&lock);
+ * obj = kzalloc(sizeof(*obj), GFP_KERNEL);
+ * if (obj) {
+ * LIST_HEAD_INIT(&obj->node);
+ * list_add(obj->node, &list):
+ * }
+ * return obj;
+ * }
+ *
+ * static void remove_free(struct object *obj)
+ * {
+ * lockdep_assert_held(&lock);
+ * list_del(&obj->node);
+ * kfree(obj);
+ * }
+ *
+ * DEFINE_FREE(remove_free, struct object *, if (_T) remove_free(_T))
+ * static int init(void)
+ * {
+ * struct object *obj __free(remove_free) = NULL;
+ * int err;
+ *
+ * guard(mutex)(&lock);
+ * obj = alloc_add();
+ *
+ * if (!obj)
+ * return -ENOMEM;
+ *
+ * err = other_init(obj);
+ * if (err)
+ * return err; // remove_free() called without the lock!!
+ *
+ * no_free_ptr(obj);
+ * return 0;
+ * }
+ *
+ * That bug is fixed by changing init() to call guard() and define +
+ * initialize @obj in this order::
+ *
+ * guard(mutex)(&lock);
+ * struct object *obj __free(remove_free) = alloc_add();
+ *
+ * Given that the "__free(...) = NULL" pattern for variables defined at
+ * the top of the function poses this potential interdependency problem
+ * the recommendation is to always define and assign variables in one
+ * statement and not group variable definitions at the top of the
+ * function when __free() is used.
+ *
+ * Lastly, given that the benefit of cleanup helpers is removal of
+ * "goto", and that the "goto" statement can jump between scopes, the
+ * expectation is that usage of "goto" and cleanup helpers is never
+ * mixed in the same function. I.e. for a given routine, convert all
+ * resources that need a "goto" cleanup to scope-based cleanup, or
+ * convert none of them.
+ */
+
/*
* DEFINE_FREE(name, type, free):
* simple helper macro that defines the required wrapper for a __free()
* DEFINE_CLASS(fdget, struct fd, fdput(_T), fdget(fd), int fd)
*
* CLASS(fdget, f)(fd);
- * if (!f.file)
+ * if (!fd_file(f))
* return -EBADF;
*
* // use 'f' without concern
#include <linux/kprobes.h>
#include <linux/lockdep.h>
#include <linux/context_tracking.h>
+#include <linux/console.h>
#include <asm/sections.h>
if (!debug_locks_off_graph_unlock())
return NULL;
+ nbcon_cpu_emergency_enter();
print_lockdep_off("BUG: MAX_STACK_TRACE_ENTRIES too low!");
dump_stack();
+ nbcon_cpu_emergency_exit();
return NULL;
}
printk("no locks held by %s/%d.\n", p->comm, task_pid_nr(p));
else
printk("%d lock%s held by %s/%d:\n", depth,
- depth > 1 ? "s" : "", p->comm, task_pid_nr(p));
+ str_plural(depth), p->comm, task_pid_nr(p));
/*
* It's not reliable to print a task's held locks if it's not sleeping
* and it's not the current task.
if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
instrumentation_begin();
debug_locks_off();
+ nbcon_cpu_emergency_enter();
printk(KERN_ERR
"BUG: looking up invalid subclass: %u\n", subclass);
printk(KERN_ERR
"turning off the locking correctness validator.\n");
dump_stack();
+ nbcon_cpu_emergency_exit();
instrumentation_end();
return NULL;
}
else {
/* Debug-check: all keys must be persistent! */
debug_locks_off();
+ nbcon_cpu_emergency_enter();
pr_err("INFO: trying to register non-static key.\n");
pr_err("The code is fine but needs lockdep annotation, or maybe\n");
pr_err("you didn't initialize this object before use?\n");
pr_err("turning off the locking correctness validator.\n");
dump_stack();
+ nbcon_cpu_emergency_exit();
return false;
}
return NULL;
}
+ nbcon_cpu_emergency_enter();
print_lockdep_off("BUG: MAX_LOCKDEP_KEYS too low!");
dump_stack();
+ nbcon_cpu_emergency_exit();
return NULL;
}
nr_lock_classes++;
if (verbose(class)) {
graph_unlock();
+ nbcon_cpu_emergency_enter();
printk("\nnew class %px: %s", class->key, class->name);
if (class->name_version > 1)
printk(KERN_CONT "#%d", class->name_version);
printk(KERN_CONT "\n");
dump_stack();
+ nbcon_cpu_emergency_exit();
if (!graph_lock()) {
return NULL;
if (!debug_locks_off_graph_unlock())
return NULL;
+ nbcon_cpu_emergency_enter();
print_lockdep_off("BUG: MAX_LOCKDEP_ENTRIES too low!");
dump_stack();
+ nbcon_cpu_emergency_exit();
return NULL;
}
nr_list_entries++;
depth = get_lock_depth(target);
+ nbcon_cpu_emergency_enter();
+
print_circular_bug_header(target, depth, check_src, check_tgt);
parent = get_lock_parent(target);
printk("\nstack backtrace:\n");
dump_stack();
+
+ nbcon_cpu_emergency_exit();
}
static noinline void print_bfs_bug(int ret)
/*
* Breadth-first-search failed, graph got corrupted?
*/
+ if (ret == BFS_EQUEUEFULL)
+ pr_warn("Increase LOCKDEP_CIRCULAR_QUEUE_BITS to avoid this warning:\n");
+
WARN(1, "lockdep bfs error:%d\n", ret);
}
if (!debug_locks_off_graph_unlock() || debug_locks_silent)
return;
+ nbcon_cpu_emergency_enter();
+
pr_warn("\n");
pr_warn("=====================================================\n");
pr_warn("WARNING: %s-safe -> %s-unsafe lock order detected\n",
pr_warn(" and %s-irq-unsafe lock:\n", irqclass);
next_root->trace = save_trace();
if (!next_root->trace)
- return;
+ goto out;
print_shortest_lock_dependencies(forwards_entry, next_root);
pr_warn("\nstack backtrace:\n");
dump_stack();
+out:
+ nbcon_cpu_emergency_exit();
}
static const char *state_names[] = {
if (!debug_locks_off_graph_unlock() || debug_locks_silent)
return;
+ nbcon_cpu_emergency_enter();
+
pr_warn("\n");
pr_warn("============================================\n");
pr_warn("WARNING: possible recursive locking detected\n");
pr_warn("\nstack backtrace:\n");
dump_stack();
+
+ nbcon_cpu_emergency_exit();
}
/*
struct held_lock *hlock_next,
struct lock_chain *chain)
{
+ nbcon_cpu_emergency_enter();
+
pr_warn("\n");
pr_warn("============================\n");
pr_warn("WARNING: chain_key collision\n");
pr_warn("\nstack backtrace:\n");
dump_stack();
+
+ nbcon_cpu_emergency_exit();
}
#endif
if (!debug_locks_off_graph_unlock())
return 0;
+ nbcon_cpu_emergency_enter();
print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!");
dump_stack();
+ nbcon_cpu_emergency_exit();
return 0;
}
chain->chain_key = chain_key;
if (!debug_locks_off_graph_unlock())
return 0;
+ nbcon_cpu_emergency_enter();
print_lockdep_off("BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!");
dump_stack();
+ nbcon_cpu_emergency_exit();
return 0;
}
if (!debug_locks_off() || debug_locks_silent)
return;
+ nbcon_cpu_emergency_enter();
+
pr_warn("\n");
pr_warn("================================\n");
pr_warn("WARNING: inconsistent lock state\n");
pr_warn("\nstack backtrace:\n");
dump_stack();
+
+ nbcon_cpu_emergency_exit();
}
/*
if (!debug_locks_off_graph_unlock() || debug_locks_silent)
return;
+ nbcon_cpu_emergency_enter();
+
pr_warn("\n");
pr_warn("========================================================\n");
pr_warn("WARNING: possible irq lock inversion dependency detected\n");
pr_warn("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
root->trace = save_trace();
if (!root->trace)
- return;
+ goto out;
print_shortest_lock_dependencies(other, root);
pr_warn("\nstack backtrace:\n");
dump_stack();
+out:
+ nbcon_cpu_emergency_exit();
}
/*
{
const struct irqtrace_events *trace = &curr->irqtrace;
+ nbcon_cpu_emergency_enter();
+
printk("irq event stamp: %u\n", trace->irq_events);
printk("hardirqs last enabled at (%u): [<%px>] %pS\n",
trace->hardirq_enable_event, (void *)trace->hardirq_enable_ip,
printk("softirqs last disabled at (%u): [<%px>] %pS\n",
trace->softirq_disable_event, (void *)trace->softirq_disable_ip,
(void *)trace->softirq_disable_ip);
+
+ nbcon_cpu_emergency_exit();
}
static int HARDIRQ_verbose(struct lock_class *class)
* We must printk outside of the graph_lock:
*/
if (ret == 2) {
+ nbcon_cpu_emergency_enter();
printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
print_lock(this);
print_irqtrace_events(curr);
dump_stack();
+ nbcon_cpu_emergency_exit();
}
return ret;
if (debug_locks_silent)
return 0;
+ nbcon_cpu_emergency_enter();
+
pr_warn("\n");
pr_warn("=============================\n");
pr_warn("[ BUG: Invalid wait context ]\n");
pr_warn("stack backtrace:\n");
dump_stack();
+ nbcon_cpu_emergency_exit();
+
return 0;
}
if (debug_locks_silent)
return;
+ nbcon_cpu_emergency_enter();
+
pr_warn("\n");
pr_warn("==================================\n");
pr_warn("WARNING: Nested lock was not taken\n");
pr_warn("\nstack backtrace:\n");
dump_stack();
+
+ nbcon_cpu_emergency_exit();
}
static int __lock_is_held(const struct lockdep_map *lock, int read);
debug_class_ops_inc(class);
if (very_verbose(class)) {
+ nbcon_cpu_emergency_enter();
printk("\nacquire class [%px] %s", class->key, class->name);
if (class->name_version > 1)
printk(KERN_CONT "#%d", class->name_version);
printk(KERN_CONT "\n");
dump_stack();
+ nbcon_cpu_emergency_exit();
}
/*
#endif
if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
debug_locks_off();
+ nbcon_cpu_emergency_enter();
print_lockdep_off("BUG: MAX_LOCK_DEPTH too low!");
printk(KERN_DEBUG "depth: %i max: %lu!\n",
curr->lockdep_depth, MAX_LOCK_DEPTH);
lockdep_print_held_locks(current);
debug_show_all_locks();
dump_stack();
+ nbcon_cpu_emergency_exit();
return 0;
}
if (debug_locks_silent)
return;
+ nbcon_cpu_emergency_enter();
+
pr_warn("\n");
pr_warn("=====================================\n");
pr_warn("WARNING: bad unlock balance detected!\n");
pr_warn("\nstack backtrace:\n");
dump_stack();
+
+ nbcon_cpu_emergency_exit();
}
static noinstr int match_held_lock(const struct held_lock *hlock,
if (debug_locks_silent)
return;
+ nbcon_cpu_emergency_enter();
+
pr_warn("\n");
pr_warn("=================================\n");
pr_warn("WARNING: bad contention detected!\n");
pr_warn("\nstack backtrace:\n");
dump_stack();
+
+ nbcon_cpu_emergency_exit();
}
static void
static void free_zapped_rcu(struct rcu_head *cb);
/*
- * Schedule an RCU callback if no RCU callback is pending. Must be called with
- * the graph lock held.
- */
- static void call_rcu_zapped(struct pending_free *pf)
+ * See if we need to queue an RCU callback, must called with
+ * the lockdep lock held, returns false if either we don't have
+ * any pending free or the callback is already scheduled.
+ * Otherwise, a call_rcu() must follow this function call.
+ */
+ static bool prepare_call_rcu_zapped(struct pending_free *pf)
{
WARN_ON_ONCE(inside_selftest());
if (list_empty(&pf->zapped))
- return;
+ return false;
if (delayed_free.scheduled)
- return;
+ return false;
delayed_free.scheduled = true;
WARN_ON_ONCE(delayed_free.pf + delayed_free.index != pf);
delayed_free.index ^= 1;
- call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
+ return true;
}
/* The caller must hold the graph lock. May be called from RCU context. */
{
struct pending_free *pf;
unsigned long flags;
+ bool need_callback;
if (WARN_ON_ONCE(ch != &delayed_free.rcu_head))
return;
pf = delayed_free.pf + (delayed_free.index ^ 1);
__free_zapped_classes(pf);
delayed_free.scheduled = false;
+ need_callback =
+ prepare_call_rcu_zapped(delayed_free.pf + delayed_free.index);
+ lockdep_unlock();
+ raw_local_irq_restore(flags);
/*
- * If there's anything on the open list, close and start a new callback.
- */
- call_rcu_zapped(delayed_free.pf + delayed_free.index);
+ * If there's pending free and its callback has not been scheduled,
+ * queue an RCU callback.
+ */
+ if (need_callback)
+ call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
- lockdep_unlock();
- raw_local_irq_restore(flags);
}
/*
{
struct pending_free *pf;
unsigned long flags;
+ bool need_callback;
init_data_structures_once();
lockdep_lock();
pf = get_pending_free();
__lockdep_free_key_range(pf, start, size);
- call_rcu_zapped(pf);
+ need_callback = prepare_call_rcu_zapped(pf);
lockdep_unlock();
raw_local_irq_restore(flags);
-
+ if (need_callback)
+ call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
/*
* Wait for any possible iterators from look_up_lock_class() to pass
* before continuing to free the memory they refer to.
struct pending_free *pf;
unsigned long flags;
int locked;
+ bool need_callback = false;
raw_local_irq_save(flags);
locked = graph_lock();
pf = get_pending_free();
__lockdep_reset_lock(pf, lock);
- call_rcu_zapped(pf);
+ need_callback = prepare_call_rcu_zapped(pf);
graph_unlock();
out_irq:
raw_local_irq_restore(flags);
+ if (need_callback)
+ call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
}
/*
struct pending_free *pf;
unsigned long flags;
bool found = false;
+ bool need_callback = false;
might_sleep();
if (found) {
pf = get_pending_free();
__lockdep_free_key_range(pf, key, 1);
- call_rcu_zapped(pf);
+ need_callback = prepare_call_rcu_zapped(pf);
}
lockdep_unlock();
raw_local_irq_restore(flags);
+ if (need_callback)
+ call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
+
/* Wait until is_dynamic_key() has finished accessing k->hash_entry. */
synchronize_rcu();
}
if (debug_locks_silent)
return;
+ nbcon_cpu_emergency_enter();
+
pr_warn("\n");
pr_warn("=========================\n");
pr_warn("WARNING: held lock freed!\n");
pr_warn("\nstack backtrace:\n");
dump_stack();
+
+ nbcon_cpu_emergency_exit();
}
static inline int not_in_range(const void* mem_from, unsigned long mem_len,
if (debug_locks_silent)
return;
+ nbcon_cpu_emergency_enter();
+
pr_warn("\n");
pr_warn("====================================\n");
pr_warn("WARNING: %s/%d still has locks held!\n",
lockdep_print_held_locks(current);
pr_warn("\nstack backtrace:\n");
dump_stack();
+
+ nbcon_cpu_emergency_exit();
}
void debug_check_no_locks_held(void)
if (unlikely(curr->lockdep_depth)) {
if (!debug_locks_off())
return;
+ nbcon_cpu_emergency_enter();
pr_warn("\n");
pr_warn("================================================\n");
pr_warn("WARNING: lock held when returning to user space!\n");
pr_warn("%s/%d is leaving the kernel with locks still held!\n",
curr->comm, curr->pid);
lockdep_print_held_locks(curr);
+ nbcon_cpu_emergency_exit();
}
/*
bool rcu = warn_rcu_enter();
/* Note: the following can be executed concurrently, so be careful. */
+ nbcon_cpu_emergency_enter();
pr_warn("\n");
pr_warn("=============================\n");
pr_warn("WARNING: suspicious RCU usage\n");
lockdep_print_held_locks(curr);
pr_warn("\nstack backtrace:\n");
dump_stack();
+ nbcon_cpu_emergency_exit();
warn_rcu_exit(rcu);
}
EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious);
projects / J-linux.git / commitdiff