lib/stackdepot: add printk_deferred_enter/exit guards

Patch series "lib/stackdepot, kasan: fixes for stack eviction series", v3.

A few fixes for the stack depot eviction series ("stackdepot: allow
evicting stack traces").

This patch (of 5):

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.

Link: https://lkml.kernel.org/r/cover.1703020707.git.andreyknvl@google.com
Link: https://lkml.kernel.org/r/82092f9040d075a161d1264377d51e0bac847e8a.1703020707.git.andreyknvl@google.com
Fixes: 108be8de ("lib/stackdepot: allow users to evict stack traces")
Fixes: cd11016e ("mm, kasan: stackdepot implementation. Enable stackdepot for SLAB")
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reported-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Closes: https://lore.kernel.org/all/000000000000f56750060b9ad216@google.com/Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

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);