Merge tag 'printk-for-6.1' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux

Pull printk updates from Petr Mladek:

 - Initialize pointer hashing using the system workqueue. It avoids
   taking locks in printk()/vsprintf() code path

 - Misc code clean up

* tag 'printk-for-6.1' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
  printk: Mark __printk percpu data ready __ro_after_init
  printk: Remove bogus comment vs. boot consoles
  printk: Remove write only variable nr_ext_console_drivers
  printk: Declare log_wait properly
  printk: Make pr_flush() static
  lib/vsprintf: Initialize vsprintf's pointer hash once the random core is ready.
  lib/vsprintf: Remove static_branch_likely() from __ptr_to_hashval().
  lib/vnsprintf: add const modifier for param 'bitmap'

1 files changed, 28 insertions, 23 deletions

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index c414a8d9f1ea9..24f37bab8bc1f 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -750,37 +750,42 @@ static int __init debug_boot_weak_hash_enable(char *str)
 }
 early_param("debug_boot_weak_hash", debug_boot_weak_hash_enable);
 
-static DEFINE_STATIC_KEY_FALSE(filled_random_ptr_key);
+static bool filled_random_ptr_key __read_mostly;
+static siphash_key_t ptr_key __read_mostly;
+static void fill_ptr_key_workfn(struct work_struct *work);
+static DECLARE_DELAYED_WORK(fill_ptr_key_work, fill_ptr_key_workfn);
 
-static void enable_ptr_key_workfn(struct work_struct *work)
+static void fill_ptr_key_workfn(struct work_struct *work)
 {
-	static_branch_enable(&filled_random_ptr_key);
+	if (!rng_is_initialized()) {
+		queue_delayed_work(system_unbound_wq, &fill_ptr_key_work, HZ  * 2);
+		return;
+	}
+
+	get_random_bytes(&ptr_key, sizeof(ptr_key));
+
+	/* Pairs with smp_rmb() before reading ptr_key. */
+	smp_wmb();
+	WRITE_ONCE(filled_random_ptr_key, true);
+}
+
+static int __init vsprintf_init_hashval(void)
+{
+	fill_ptr_key_workfn(NULL);
+	return 0;
 }
+subsys_initcall(vsprintf_init_hashval)
 
 /* Maps a pointer to a 32 bit unique identifier. */
 static inline int __ptr_to_hashval(const void *ptr, unsigned long *hashval_out)
 {
-	static siphash_key_t ptr_key __read_mostly;
 	unsigned long hashval;
 
-	if (!static_branch_likely(&filled_random_ptr_key)) {
-		static bool filled = false;
-		static DEFINE_SPINLOCK(filling);
-		static DECLARE_WORK(enable_ptr_key_work, enable_ptr_key_workfn);
-		unsigned long flags;
-
-		if (!system_unbound_wq || !rng_is_initialized() ||
-		    !spin_trylock_irqsave(&filling, flags))
-			return -EAGAIN;
-
-		if (!filled) {
-			get_random_bytes(&ptr_key, sizeof(ptr_key));
-			queue_work(system_unbound_wq, &enable_ptr_key_work);
-			filled = true;
-		}
-		spin_unlock_irqrestore(&filling, flags);
-	}
+	if (!READ_ONCE(filled_random_ptr_key))
+		return -EBUSY;
 
+	/* Pairs with smp_wmb() after writing ptr_key. */
+	smp_rmb();
 
 #ifdef CONFIG_64BIT
 	hashval = (unsigned long)siphash_1u64((u64)ptr, &ptr_key);
@@ -1189,7 +1194,7 @@ char *hex_string(char *buf, char *end, u8 *addr, struct printf_spec spec,
 }
 
 static noinline_for_stack
-char *bitmap_string(char *buf, char *end, unsigned long *bitmap,
+char *bitmap_string(char *buf, char *end, const unsigned long *bitmap,
 		    struct printf_spec spec, const char *fmt)
 {
 	const int CHUNKSZ = 32;
@@ -1233,7 +1238,7 @@ char *bitmap_string(char *buf, char *end, unsigned long *bitmap,
 }
 
 static noinline_for_stack
-char *bitmap_list_string(char *buf, char *end, unsigned long *bitmap,
+char *bitmap_list_string(char *buf, char *end, const unsigned long *bitmap,
 			 struct printf_spec spec, const char *fmt)
 {
 	int nr_bits = max_t(int, spec.field_width, 0);