syzbot is sometimes getting mixed output like below due to concurrent
printk(). Mitigate such output by using line-buffered printk() API.
RCU used illegally from idle CPU!
rcu_scheduler_active = 2, debug_locks = 1
RSP: 0018:ffffffff88007bb8 EFLAGS: 00000286
RCU used illegally from extended quiescent state!
ORIG_RAX: ffffffffffffff13
1 lock held by swapper/1/0:
RAX: dffffc0000000000 RBX: 1ffffffff1000f7b RCX: 0000000000000000
#0:
RDX: 1ffffffff10237b8 RSI: 0000000000000001 RDI: ffffffff8811bdc0
000000004b34587c
RBP: ffffffff88007bb8 R08: ffffffff88075e00 R09: 0000000000000000
(
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
rcu_read_lock
R13: ffffffff88007c78 R14: 0000000000000000 R15: 0000000000000000
){....}
arch_safe_halt arch/x86/include/asm/paravirt.h:94 [inline]
default_idle+0xc2/0x410 arch/x86/kernel/process.c:498
, at: trace_call_bpf+0xf8/0x640 kernel/trace/bpf_trace.c:46
Signed-off-by: Tetsuo Handa <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Will Deacon <[email protected]>
---
kernel/locking/lockdep.c | 268 +++++++++++++++++++++++++++--------------------
1 file changed, 155 insertions(+), 113 deletions(-)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 1efada2..fbc127d 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -493,7 +493,8 @@ void get_usage_chars(struct lock_class *class, char
usage[LOCK_USAGE_CHARS])
usage[i] = '\0';
}
-static void __print_lock_name(struct lock_class *class)
+static void __print_lock_name(struct lock_class *class,
+ struct printk_buffer *buf)
{
char str[KSYM_NAME_LEN];
const char *name;
@@ -501,25 +502,25 @@ static void __print_lock_name(struct lock_class *class)
name = class->name;
if (!name) {
name = __get_key_name(class->key, str);
- printk(KERN_CONT "%s", name);
+ printk_buffered(buf, "%s", name);
} else {
- printk(KERN_CONT "%s", name);
+ printk_buffered(buf, "%s", name);
if (class->name_version > 1)
- printk(KERN_CONT "#%d", class->name_version);
+ printk_buffered(buf, "#%d", class->name_version);
if (class->subclass)
- printk(KERN_CONT "/%d", class->subclass);
+ printk_buffered(buf, "/%d", class->subclass);
}
}
-static void print_lock_name(struct lock_class *class)
+static void print_lock_name(struct lock_class *class, struct printk_buffer
*buf)
{
char usage[LOCK_USAGE_CHARS];
get_usage_chars(class, usage);
- printk(KERN_CONT " (");
- __print_lock_name(class);
- printk(KERN_CONT "){%s}", usage);
+ printk_buffered(buf, " (");
+ __print_lock_name(class, buf);
+ printk_buffered(buf, "){%s}", usage);
}
static void print_lockdep_cache(struct lockdep_map *lock)
@@ -534,8 +535,9 @@ static void print_lockdep_cache(struct lockdep_map *lock)
printk(KERN_CONT "%s", name);
}
-static void print_lock(struct held_lock *hlock)
+static void print_lock(struct held_lock *hlock, struct printk_buffer *buf)
{
+ bool free = false;
/*
* We can be called locklessly through debug_show_all_locks() so be
* extra careful, the hlock might have been released and cleared.
@@ -546,17 +548,24 @@ static void print_lock(struct held_lock *hlock)
barrier();
if (!class_idx || (class_idx - 1) >= MAX_LOCKDEP_KEYS) {
- printk(KERN_CONT "<RELEASED>\n");
+ printk_buffered(buf, "<RELEASED>\n");
return;
}
- printk(KERN_CONT "%p", hlock->instance);
- print_lock_name(lock_classes + class_idx - 1);
- printk(KERN_CONT ", at: %pS\n", (void *)hlock->acquire_ip);
+ if (!buf) {
+ free = true;
+ buf = get_printk_buffer();
+ }
+ printk_buffered(buf, "%p", hlock->instance);
+ print_lock_name(lock_classes + class_idx - 1, buf);
+ printk_buffered(buf, ", at: %pS\n", (void *)hlock->acquire_ip);
+ if (free)
+ put_printk_buffer(buf);
}
static void lockdep_print_held_locks(struct task_struct *p)
{
+ struct printk_buffer *buf;
int i, depth = READ_ONCE(p->lockdep_depth);
if (!depth)
@@ -570,10 +579,12 @@ static void lockdep_print_held_locks(struct task_struct
*p)
*/
if (p->state == TASK_RUNNING && p != current)
return;
+ buf = get_printk_buffer();
for (i = 0; i < depth; i++) {
- printk(" #%d: ", i);
- print_lock(p->held_locks + i);
+ printk_buffered(buf, " #%d: ", i);
+ print_lock(p->held_locks + i, buf);
}
+ put_printk_buffer(buf);
}
static void print_kernel_ident(void)
@@ -1083,12 +1094,16 @@ static inline int __bfs_backwards(struct lock_list
*src_entry,
static noinline int
print_circular_bug_entry(struct lock_list *target, int depth)
{
+ struct printk_buffer *buf;
+
if (debug_locks_silent)
return 0;
- printk("\n-> #%u", depth);
- print_lock_name(target->class);
- printk(KERN_CONT ":\n");
+ buf = get_printk_buffer();
+ printk_buffered(buf, "\n-> #%u", depth);
+ print_lock_name(target->class, buf);
+ printk_buffered(buf, ":\n");
print_stack_trace(&target->trace, 6);
+ put_printk_buffer(buf);
return 0;
}
@@ -1098,6 +1113,7 @@ static inline int __bfs_backwards(struct lock_list
*src_entry,
struct held_lock *tgt,
struct lock_list *prt)
{
+ struct printk_buffer *buf = get_printk_buffer();
struct lock_class *source = hlock_class(src);
struct lock_class *target = hlock_class(tgt);
struct lock_class *parent = prt->class;
@@ -1116,31 +1132,32 @@ static inline int __bfs_backwards(struct lock_list
*src_entry,
* from the safe_class lock to the unsafe_class lock.
*/
if (parent != source) {
- printk("Chain exists of:\n ");
- __print_lock_name(source);
- printk(KERN_CONT " --> ");
- __print_lock_name(parent);
- printk(KERN_CONT " --> ");
- __print_lock_name(target);
- printk(KERN_CONT "\n\n");
+ printk_buffered(buf, "Chain exists of:\n ");
+ __print_lock_name(source, buf);
+ printk_buffered(buf, " --> ");
+ __print_lock_name(parent, buf);
+ printk_buffered(buf, " --> ");
+ __print_lock_name(target, buf);
+ printk_buffered(buf, "\n\n");
}
printk(" Possible unsafe locking scenario:\n\n");
printk(" CPU0 CPU1\n");
printk(" ---- ----\n");
- printk(" lock(");
- __print_lock_name(target);
- printk(KERN_CONT ");\n");
+ printk_buffered(buf, " lock(");
+ __print_lock_name(target, buf);
+ printk_buffered(buf, ");\n");
printk(" lock(");
- __print_lock_name(parent);
- printk(KERN_CONT ");\n");
- printk(" lock(");
- __print_lock_name(target);
- printk(KERN_CONT ");\n");
- printk(" lock(");
- __print_lock_name(source);
- printk(KERN_CONT ");\n");
+ __print_lock_name(parent, buf);
+ printk_buffered(buf, ");\n");
+ printk_buffered(buf, " lock(");
+ __print_lock_name(target, buf);
+ printk_buffered(buf, ");\n");
+ printk_buffered(buf, " lock(");
+ __print_lock_name(source, buf);
+ printk_buffered(buf, ");\n");
printk("\n *** DEADLOCK ***\n\n");
+ put_printk_buffer(buf);
}
/*
@@ -1164,11 +1181,11 @@ static inline int __bfs_backwards(struct lock_list
*src_entry,
pr_warn("------------------------------------------------------\n");
pr_warn("%s/%d is trying to acquire lock:\n",
curr->comm, task_pid_nr(curr));
- print_lock(check_src);
+ print_lock(check_src, NULL);
pr_warn("\nbut task is already holding lock:\n");
- print_lock(check_tgt);
+ print_lock(check_tgt, NULL);
pr_warn("\nwhich lock already depends on the new lock.\n\n");
pr_warn("\nthe existing dependency chain (in reverse order) is:\n");
@@ -1387,21 +1404,23 @@ static inline int usage_match(struct lock_list *entry,
void *bit)
static void print_lock_class_header(struct lock_class *class, int depth)
{
+ struct printk_buffer *buf = get_printk_buffer();
int bit;
- printk("%*s->", depth, "");
- print_lock_name(class);
+ printk_buffered(buf, "%*s->", depth, "");
+ print_lock_name(class, buf);
#ifdef CONFIG_DEBUG_LOCKDEP
- printk(KERN_CONT " ops: %lu", debug_class_ops_read(class));
+ printk_buffered(buf, " ops: %lu", debug_class_ops_read(class));
#endif
- printk(KERN_CONT " {\n");
+ printk_buffered(buf, " {\n");
for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
if (class->usage_mask & (1 << bit)) {
int len = depth;
- len += printk("%*s %s", depth, "", usage_str[bit]);
- len += printk(KERN_CONT " at:\n");
+ len += printk_buffered(buf, "%*s %s", depth, "",
+ usage_str[bit]);
+ len += printk_buffered(buf, " at:\n");
print_stack_trace(class->usage_traces + bit, len);
}
}
@@ -1409,6 +1428,7 @@ static void print_lock_class_header(struct lock_class
*class, int depth)
printk("%*s ... key at: [<%px>] %pS\n",
depth, "", class->key, class->key);
+ put_printk_buffer(buf);
}
/*
@@ -1451,6 +1471,7 @@ static void print_lock_class_header(struct lock_class
*class, int depth)
struct lock_class *safe_class = safe_entry->class;
struct lock_class *unsafe_class = unsafe_entry->class;
struct lock_class *middle_class = prev_class;
+ struct printk_buffer *buf = get_printk_buffer();
if (middle_class == safe_class)
middle_class = next_class;
@@ -1469,33 +1490,34 @@ static void print_lock_class_header(struct lock_class
*class, int depth)
* from the safe_class lock to the unsafe_class lock.
*/
if (middle_class != unsafe_class) {
- printk("Chain exists of:\n ");
- __print_lock_name(safe_class);
- printk(KERN_CONT " --> ");
- __print_lock_name(middle_class);
- printk(KERN_CONT " --> ");
- __print_lock_name(unsafe_class);
- printk(KERN_CONT "\n\n");
+ printk_buffered(buf, "Chain exists of:\n ");
+ __print_lock_name(safe_class, buf);
+ printk_buffered(buf, " --> ");
+ __print_lock_name(middle_class, buf);
+ printk_buffered(buf, " --> ");
+ __print_lock_name(unsafe_class, buf);
+ printk_buffered(buf, "\n\n");
}
printk(" Possible interrupt unsafe locking scenario:\n\n");
printk(" CPU0 CPU1\n");
printk(" ---- ----\n");
- printk(" lock(");
- __print_lock_name(unsafe_class);
- printk(KERN_CONT ");\n");
+ printk_buffered(buf, " lock(");
+ __print_lock_name(unsafe_class, buf);
+ printk_buffered(buf, ");\n");
printk(" local_irq_disable();\n");
- printk(" lock(");
- __print_lock_name(safe_class);
- printk(KERN_CONT ");\n");
- printk(" lock(");
- __print_lock_name(middle_class);
- printk(KERN_CONT ");\n");
+ printk_buffered(buf, " lock(");
+ __print_lock_name(safe_class, buf);
+ printk_buffered(buf, ");\n");
+ printk_buffered(buf, " lock(");
+ __print_lock_name(middle_class, buf);
+ printk_buffered(buf, ");\n");
printk(" <Interrupt>\n");
- printk(" lock(");
- __print_lock_name(safe_class);
- printk(KERN_CONT ");\n");
+ printk_buffered(buf, " lock(");
+ __print_lock_name(safe_class, buf);
+ printk_buffered(buf, ");\n");
printk("\n *** DEADLOCK ***\n\n");
+ put_printk_buffer(buf);
}
static int
@@ -1510,9 +1532,12 @@ static void print_lock_class_header(struct lock_class
*class, int depth)
enum lock_usage_bit bit2,
const char *irqclass)
{
+ struct printk_buffer *buf;
+
if (!debug_locks_off_graph_unlock() || debug_locks_silent)
return 0;
+ buf = get_printk_buffer();
pr_warn("\n");
pr_warn("=====================================================\n");
pr_warn("WARNING: %s-safe -> %s-unsafe lock order detected\n",
@@ -1525,26 +1550,26 @@ static void print_lock_class_header(struct lock_class
*class, int depth)
curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
curr->hardirqs_enabled,
curr->softirqs_enabled);
- print_lock(next);
+ print_lock(next, buf);
pr_warn("\nand this task is already holding:\n");
- print_lock(prev);
+ print_lock(prev, buf);
pr_warn("which would create a new lock dependency:\n");
- print_lock_name(hlock_class(prev));
- pr_cont(" ->");
- print_lock_name(hlock_class(next));
- pr_cont("\n");
+ print_lock_name(hlock_class(prev), buf);
+ bpr_cont(buf, " ->");
+ print_lock_name(hlock_class(next), buf);
+ bpr_cont(buf, "\n");
pr_warn("\nbut this new dependency connects a %s-irq-safe lock:\n",
irqclass);
- print_lock_name(backwards_entry->class);
- pr_warn("\n... which became %s-irq-safe at:\n", irqclass);
+ print_lock_name(backwards_entry->class, buf);
+ bpr_warn(buf, "\n... which became %s-irq-safe at:\n", irqclass);
print_stack_trace(backwards_entry->class->usage_traces + bit1, 1);
pr_warn("\nto a %s-irq-unsafe lock:\n", irqclass);
- print_lock_name(forwards_entry->class);
- pr_warn("\n... which became %s-irq-unsafe at:\n", irqclass);
+ print_lock_name(forwards_entry->class, buf);
+ bpr_warn(buf, "\n... which became %s-irq-unsafe at:\n", irqclass);
pr_warn("...");
print_stack_trace(forwards_entry->class->usage_traces + bit2, 1);
@@ -1557,18 +1582,20 @@ static void print_lock_class_header(struct lock_class
*class, int depth)
pr_warn("\nthe dependencies between %s-irq-safe lock and the holding
lock:\n", irqclass);
if (!save_trace(&prev_root->trace))
- return 0;
+ goto done;
print_shortest_lock_dependencies(backwards_entry, prev_root);
pr_warn("\nthe dependencies between the lock to be acquired");
pr_warn(" and %s-irq-unsafe lock:\n", irqclass);
if (!save_trace(&next_root->trace))
- return 0;
+ goto done;
print_shortest_lock_dependencies(forwards_entry, next_root);
pr_warn("\nstack backtrace:\n");
dump_stack();
+ done:
+ put_printk_buffer(buf);
return 0;
}
@@ -1721,18 +1748,20 @@ static inline void inc_chains(void)
{
struct lock_class *next = hlock_class(nxt);
struct lock_class *prev = hlock_class(prv);
+ struct printk_buffer *buf = get_printk_buffer();
printk(" Possible unsafe locking scenario:\n\n");
printk(" CPU0\n");
printk(" ----\n");
- printk(" lock(");
- __print_lock_name(prev);
- printk(KERN_CONT ");\n");
- printk(" lock(");
- __print_lock_name(next);
- printk(KERN_CONT ");\n");
+ printk_buffered(buf, " lock(");
+ __print_lock_name(prev, buf);
+ printk_buffered(buf, ");\n");
+ printk_buffered(buf, " lock(");
+ __print_lock_name(next, buf);
+ printk_buffered(buf, ");\n");
printk("\n *** DEADLOCK ***\n\n");
printk(" May be due to missing lock nesting notation\n\n");
+ put_printk_buffer(buf);
}
static int
@@ -1749,9 +1778,9 @@ static inline void inc_chains(void)
pr_warn("--------------------------------------------\n");
pr_warn("%s/%d is trying to acquire lock:\n",
curr->comm, task_pid_nr(curr));
- print_lock(next);
+ print_lock(next, NULL);
pr_warn("\nbut task is already holding lock:\n");
- print_lock(prev);
+ print_lock(prev, NULL);
pr_warn("\nother info that might help us debug this:\n");
print_deadlock_scenario(next, prev);
@@ -2048,18 +2077,20 @@ static inline int get_first_held_lock(struct
task_struct *curr,
/*
* Returns the next chain_key iteration
*/
-static u64 print_chain_key_iteration(int class_idx, u64 chain_key)
+static u64 print_chain_key_iteration(int class_idx, u64 chain_key,
+ struct printk_buffer *buf)
{
u64 new_chain_key = iterate_chain_key(chain_key, class_idx);
- printk(" class_idx:%d -> chain_key:%016Lx",
+ printk_buffered(buf, " class_idx:%d -> chain_key:%016Lx",
class_idx,
(unsigned long long)new_chain_key);
return new_chain_key;
}
-static void
-print_chain_keys_held_locks(struct task_struct *curr, struct held_lock
*hlock_next)
+static void print_chain_keys_held_locks(struct task_struct *curr,
+ struct held_lock *hlock_next,
+ struct printk_buffer *buf)
{
struct held_lock *hlock;
u64 chain_key = 0;
@@ -2069,16 +2100,18 @@ static u64 print_chain_key_iteration(int class_idx, u64
chain_key)
printk("depth: %u\n", depth + 1);
for (i = get_first_held_lock(curr, hlock_next); i < depth; i++) {
hlock = curr->held_locks + i;
- chain_key = print_chain_key_iteration(hlock->class_idx,
chain_key);
+ chain_key = print_chain_key_iteration(hlock->class_idx,
+ chain_key, buf);
- print_lock(hlock);
+ print_lock(hlock, buf);
}
- print_chain_key_iteration(hlock_next->class_idx, chain_key);
- print_lock(hlock_next);
+ print_chain_key_iteration(hlock_next->class_idx, chain_key, buf);
+ print_lock(hlock_next, buf);
}
-static void print_chain_keys_chain(struct lock_chain *chain)
+static void print_chain_keys_chain(struct lock_chain *chain,
+ struct printk_buffer *buf)
{
int i;
u64 chain_key = 0;
@@ -2087,10 +2120,11 @@ static void print_chain_keys_chain(struct lock_chain
*chain)
printk("depth: %u\n", chain->depth);
for (i = 0; i < chain->depth; i++) {
class_id = chain_hlocks[chain->base + i];
- chain_key = print_chain_key_iteration(class_id + 1, chain_key);
+ chain_key = print_chain_key_iteration(class_id + 1, chain_key,
+ buf);
- print_lock_name(lock_classes + class_id);
- printk("\n");
+ print_lock_name(lock_classes + class_id, buf);
+ printk_buffered(buf, "\n");
}
}
@@ -2098,6 +2132,8 @@ static void print_collision(struct task_struct *curr,
struct held_lock *hlock_next,
struct lock_chain *chain)
{
+ struct printk_buffer *buf = get_printk_buffer();
+
pr_warn("\n");
pr_warn("============================\n");
pr_warn("WARNING: chain_key collision\n");
@@ -2106,14 +2142,15 @@ static void print_collision(struct task_struct *curr,
pr_warn("%s/%d: ", current->comm, task_pid_nr(current));
pr_warn("Hash chain already cached but the contents don't match!\n");
- pr_warn("Held locks:");
- print_chain_keys_held_locks(curr, hlock_next);
+ bpr_warn(buf, "Held locks:");
+ print_chain_keys_held_locks(curr, hlock_next, buf);
- pr_warn("Locks in cached chain:");
- print_chain_keys_chain(chain);
+ bpr_warn(buf, "Locks in cached chain:");
+ print_chain_keys_chain(chain, buf);
pr_warn("\nstack backtrace:\n");
dump_stack();
+ put_printk_buffer(buf);
}
#endif
@@ -2421,18 +2458,20 @@ static void check_chain_key(struct task_struct *curr)
print_usage_bug_scenario(struct held_lock *lock)
{
struct lock_class *class = hlock_class(lock);
+ struct printk_buffer *buf = get_printk_buffer();
printk(" Possible unsafe locking scenario:\n\n");
printk(" CPU0\n");
printk(" ----\n");
- printk(" lock(");
- __print_lock_name(class);
- printk(KERN_CONT ");\n");
+ printk_buffered(buf, " lock(");
+ __print_lock_name(class, buf);
+ printk_buffered(buf, ");\n");
printk(" <Interrupt>\n");
- printk(" lock(");
- __print_lock_name(class);
- printk(KERN_CONT ");\n");
+ printk_buffered(buf, " lock(");
+ __print_lock_name(class, buf);
+ printk_buffered(buf, ");\n");
printk("\n *** DEADLOCK ***\n\n");
+ put_printk_buffer(buf);
}
static int
@@ -2457,7 +2496,7 @@ static void check_chain_key(struct task_struct *curr)
trace_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
trace_hardirqs_enabled(curr),
trace_softirqs_enabled(curr));
- print_lock(this);
+ print_lock(this, NULL);
pr_warn("{%s} state was registered at:\n", usage_str[prev_bit]);
print_stack_trace(hlock_class(this)->usage_traces + prev_bit, 1);
@@ -2500,6 +2539,7 @@ static int mark_lock(struct task_struct *curr, struct
held_lock *this,
struct held_lock *this, int forwards,
const char *irqclass)
{
+ struct printk_buffer *buf;
struct lock_list *entry = other;
struct lock_list *middle = NULL;
int depth;
@@ -2514,13 +2554,15 @@ static int mark_lock(struct task_struct *curr, struct
held_lock *this,
pr_warn("--------------------------------------------------------\n");
pr_warn("%s/%d just changed the state of lock:\n",
curr->comm, task_pid_nr(curr));
- print_lock(this);
+ print_lock(this, NULL);
if (forwards)
pr_warn("but this lock took another, %s-unsafe lock in the
past:\n", irqclass);
else
pr_warn("but this lock was taken by another, %s-safe lock in
the past:\n", irqclass);
- print_lock_name(other->class);
- pr_warn("\n\nand interrupts could create inverse lock ordering between
them.\n\n");
+ buf = get_printk_buffer();
+ print_lock_name(other->class, buf);
+ bpr_warn(buf, "\n\nand interrupts could create inverse lock ordering
between them.\n\n");
+ put_printk_buffer(buf);
pr_warn("\nother info that might help us debug this:\n");
@@ -3077,7 +3119,7 @@ static int mark_lock(struct task_struct *curr, struct
held_lock *this,
*/
if (ret == 2) {
printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
- print_lock(this);
+ print_lock(this, NULL);
print_irqtrace_events(curr);
dump_stack();
}
@@ -3172,7 +3214,7 @@ void lockdep_init_map(struct lockdep_map *lock, const
char *name,
pr_warn("----------------------------------\n");
pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
- print_lock(hlock);
+ print_lock(hlock, NULL);
pr_warn("\nbut this task is not holding:\n");
pr_warn("%s\n", hlock->nest_lock->name);
@@ -4300,7 +4342,7 @@ void __init lockdep_init(void)
pr_warn("-------------------------\n");
pr_warn("%s/%d is freeing memory %px-%px, with a lock still held
there!\n",
curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
- print_lock(hlock);
+ print_lock(hlock, NULL);
lockdep_print_held_locks(curr);
pr_warn("\nstack backtrace:\n");
--
1.8.3.1
