printk changes for 6.1

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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'

fs/proc/kmsg.c

@@ -17,8 +17,6 @@
 
 #include <asm/io.h>
 
-extern wait_queue_head_t log_wait;
-
 static int kmsg_open(struct inode * inode, struct file * file)
 {
 	return do_syslog(SYSLOG_ACTION_OPEN, NULL, 0, SYSLOG_FROM_PROC);

include/linux/printk.h

@@ -169,8 +169,6 @@ extern void __printk_safe_exit(void);
 #define printk_deferred_enter __printk_safe_enter
 #define printk_deferred_exit __printk_safe_exit
 
-extern bool pr_flush(int timeout_ms, bool reset_on_progress);
-
 /*
  * Please don't use printk_ratelimit(), because it shares ratelimiting state
  * with all other unrelated printk_ratelimit() callsites.  Instead use
@@ -221,11 +219,6 @@ static inline void printk_deferred_exit(void)
 {
 }
 
-static inline bool pr_flush(int timeout_ms, bool reset_on_progress)
-{
-	return true;
-}
-
 static inline int printk_ratelimit(void)
 {
 	return 0;

include/linux/syslog.h

@@ -8,6 +8,8 @@
 #ifndef _LINUX_SYSLOG_H
 #define _LINUX_SYSLOG_H
 
+#include <linux/wait.h>
+
 /* Close the log.  Currently a NOP. */
 #define SYSLOG_ACTION_CLOSE          0
 /* Open the log. Currently a NOP. */
@@ -35,5 +37,6 @@
 #define SYSLOG_FROM_PROC             1
 
 int do_syslog(int type, char __user *buf, int count, int source);
+extern wait_queue_head_t log_wait;
 
 #endif /* _LINUX_SYSLOG_H */

kernel/printk/printk.c

@@ -220,9 +220,6 @@ int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write,
 }
 #endif /* CONFIG_PRINTK && CONFIG_SYSCTL */
 
-/* Number of registered extended console drivers. */
-static int nr_ext_console_drivers;
-
 /*
  * Helper macros to handle lockdep when locking/unlocking console_sem. We use
  * macros instead of functions so that _RET_IP_ contains useful information.
@@ -433,7 +430,7 @@ static struct printk_ringbuffer *prb = &printk_rb_static;
  * per_cpu_areas are initialised. This variable is set to true when
  * it's safe to access per-CPU data.
  */
-static bool __printk_percpu_data_ready __read_mostly;
+static bool __printk_percpu_data_ready __ro_after_init;
 
 bool printk_percpu_data_ready(void)
 {
@@ -2296,6 +2293,7 @@ asmlinkage __visible int _printk(const char *fmt, ...)
 }
 EXPORT_SYMBOL(_printk);
 
+static bool pr_flush(int timeout_ms, bool reset_on_progress);
 static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress);
 
 #else /* CONFIG_PRINTK */
@@ -2330,6 +2328,7 @@ static void call_console_driver(struct console *con, const char *text, size_t le
 {
 }
 static bool suppress_message_printing(int level) { return false; }
+static bool pr_flush(int timeout_ms, bool reset_on_progress) { return true; }
 static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress) { return true; }
 
 #endif /* CONFIG_PRINTK */
@@ -3186,9 +3185,6 @@ void register_console(struct console *newcon)
 		console_drivers->next = newcon;
 	}
 
-	if (newcon->flags & CON_EXTENDED)
-		nr_ext_console_drivers++;
-
 	newcon->dropped = 0;
 	if (newcon->flags & CON_PRINTBUFFER) {
 		/* Get a consistent copy of @syslog_seq. */
@@ -3213,9 +3209,6 @@ void register_console(struct console *newcon)
 	if (bootcon_enabled &&
 	    ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
 	    !keep_bootcon) {
-		/* We need to iterate through all boot consoles, to make
-		 * sure we print everything out, before we unregister them.
-		 */
 		for_each_console(con)
 			if (con->flags & CON_BOOT)
 				unregister_console(con);
@@ -3254,9 +3247,6 @@ int unregister_console(struct console *console)
 	if (res)
 		goto out_disable_unlock;
 
-	if (console->flags & CON_EXTENDED)
-		nr_ext_console_drivers--;
-
 	/*
 	 * If this isn't the last console and it has CON_CONSDEV set, we
 	 * need to set it on the next preferred console.
@@ -3438,11 +3428,10 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre
  * Context: Process context. May sleep while acquiring console lock.
  * Return: true if all enabled printers are caught up.
  */
-bool pr_flush(int timeout_ms, bool reset_on_progress)
+static bool pr_flush(int timeout_ms, bool reset_on_progress)
 {
 	return __pr_flush(NULL, timeout_ms, reset_on_progress);
 }
-EXPORT_SYMBOL(pr_flush);
 
 /*
  * Delayed printk version, for scheduler-internal messages:

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)) {
+	if (!READ_ONCE(filled_random_ptr_key))
-		static bool filled = false;
+		return -EBUSY;
-		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);
-	}
 
+	/* 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);