[PATCH mm 1/4] lib/stackdepot: add printk_deferred_enter/exit guards

From: andrey . konovalov
Date: Mon Dec 11 2023 - 19:15:09 EST


From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>

Stack depot functions can be called from various contexts that do
allocations, including with console locks taken. At the same time, stack
depot functions might print WARNING's or refcount-related failures.

This can cause a deadlock on console locks.

Add printk_deferred_enter/exit guards to stack depot to avoid this.

Reported-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Closes: https://lore.kernel.org/all/000000000000f56750060b9ad216@xxxxxxxxxx/
Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
---
lib/stackdepot.c | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index 870cce2f4cbd..a0be5d05c7f0 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -506,12 +506,14 @@ depot_stack_handle_t stack_depot_save_flags(unsigned long *entries,
bucket = &stack_table[hash & stack_hash_mask];

read_lock_irqsave(&pool_rwlock, flags);
+ printk_deferred_enter();

/* Fast path: look the stack trace up without full locking. */
found = find_stack(bucket, entries, nr_entries, hash);
if (found) {
if (depot_flags & STACK_DEPOT_FLAG_GET)
refcount_inc(&found->count);
+ printk_deferred_exit();
read_unlock_irqrestore(&pool_rwlock, flags);
goto exit;
}
@@ -520,6 +522,7 @@ depot_stack_handle_t stack_depot_save_flags(unsigned long *entries,
if (new_pool_required)
need_alloc = true;

+ printk_deferred_exit();
read_unlock_irqrestore(&pool_rwlock, flags);

/*
@@ -541,6 +544,7 @@ depot_stack_handle_t stack_depot_save_flags(unsigned long *entries,
}

write_lock_irqsave(&pool_rwlock, flags);
+ printk_deferred_enter();

found = find_stack(bucket, entries, nr_entries, hash);
if (!found) {
@@ -562,6 +566,7 @@ depot_stack_handle_t stack_depot_save_flags(unsigned long *entries,
depot_keep_new_pool(&prealloc);
}

+ printk_deferred_exit();
write_unlock_irqrestore(&pool_rwlock, flags);
exit:
if (prealloc) {
@@ -600,9 +605,11 @@ unsigned int stack_depot_fetch(depot_stack_handle_t handle,
return 0;

read_lock_irqsave(&pool_rwlock, flags);
+ printk_deferred_enter();

stack = depot_fetch_stack(handle);

+ printk_deferred_exit();
read_unlock_irqrestore(&pool_rwlock, flags);

*entries = stack->entries;
@@ -619,6 +626,7 @@ void stack_depot_put(depot_stack_handle_t handle)
return;

write_lock_irqsave(&pool_rwlock, flags);
+ printk_deferred_enter();

stack = depot_fetch_stack(handle);
if (WARN_ON(!stack))
@@ -633,6 +641,7 @@ void stack_depot_put(depot_stack_handle_t handle)
}

out:
+ printk_deferred_exit();
write_unlock_irqrestore(&pool_rwlock, flags);
}
EXPORT_SYMBOL_GPL(stack_depot_put);
--
2.25.1