Merge tag 'printk-for-7.4' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux

Pull printk updates from Petr Mladek:

 - John Ogness became PRINTK co-maintainer

 - Unregister boot consoles when any proper console is registered at the
   end of the boot phase. Before they were removed only when the
   so-called preferred console, usually set via the last 'console='
   parameter, got registered

 - Fix computation for increasing the printk ringbuffer on systems with
   many CPUs and possibly long backtraces from all CPUs

 - Cleaned up irq_works handling for deferred printk operations

 - Use acquire/release semantic for filled_random_ptr_key

 - Allow to use ':' in console options

 - More code clean up

* tag 'printk-for-7.4' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
  MAINTAINERS: Make John PRINTK co-maintainer
  lib/vsprintf: Use EXPORT_SYMBOL_IF_KUNIT() to export symbols
  printk: Remove console options before decoding the name
  printk: increase the ring buffer for more than 16 CPUs by default
  printk_ringbuffer: Avoid needless read of prb_desc
  printk: Use two irq_works instead per-CPU
  lib/vsprintf: Use acquire/release for ptr_key publication
  printk: Remove remaining boot consoles when a real console exists

MAINTAINERS

@@ -21961,8 +21961,8 @@ F:	scripts/Makefile.propeller
 
 PRINTK
 M:	Petr Mladek <pmladek@suse.com>
+M:	John Ogness <john.ogness@linutronix.de>
 R:	Steven Rostedt <rostedt@goodmis.org>
-R:	John Ogness <john.ogness@linutronix.de>
 R:	Sergey Senozhatsky <senozhatsky@chromium.org>
 S:	Maintained
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux.git

kernel/printk/printk.c

@@ -1085,9 +1085,9 @@ static void __init log_buf_add_cpu(void)
 	if (num_possible_cpus() == 1)
 		return;
 
-	cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN;
+	cpu_extra = num_possible_cpus() * __LOG_CPU_MAX_BUF_LEN;
 
-	/* by default this will only continue through for large > 64 CPUs */
+	/* by default this will only continue through for more than 16 CPUs */
 	if (cpu_extra <= __LOG_BUF_LEN / 2)
 		return;
 
@@ -2646,24 +2646,25 @@ static int __init console_setup(char *str)
 	if (_braille_console_setup(&str, &brl_options))
 		return 1;
 
+	/*
+	 * Decode str into name, index and options. Start with options, since
+	 * it might also contain a ':' used for DEVNAME.
+	 */
+	options = strchr(str, ',');
+	if (options)
+		*(options++) = 0;
+
 	/* For a DEVNAME:0.0 style console the character device is unknown early */
 	if (strchr(str, ':'))
 		devname = buf;
 	else
 		ttyname = buf;
 
-	/*
-	 * Decode str into name, index, options.
-	 */
 	if (ttyname && isdigit(str[0]))
 		scnprintf(buf, sizeof(buf), "ttyS%s", str);
 	else
 		strscpy(buf, str);
 
-	options = strchr(str, ',');
-	if (options)
-		*(options++) = 0;
-
 #ifdef __sparc__
 	if (!strcmp(str, "ttya"))
 		strscpy(buf, "ttyS0");
@@ -2671,17 +2672,18 @@ static int __init console_setup(char *str)
 		strscpy(buf, "ttyS1");
 #endif
 
-	for (s = buf; *s; s++)
-		if ((ttyname && isdigit(*s)) || *s == ',')
-			break;
-
-	/* @idx will get defined when devname matches. */
-	if (devname)
-		idx = -1;
-	else
+	if (ttyname) {
+		/* Detect @idx in ttyname and remove it. */
+		for (s = ttyname; *s; s++) {
+			if (isdigit(*s))
+				break;
+		}
 		idx = simple_strtoul(s, NULL, 10);
-
-	*s = 0;
+		*s = 0;
+	} else {
+		/* @idx will get defined when devname matches. */
+		idx = -1;
+	}
 
 	__add_preferred_console(ttyname, idx, devname, options, brl_options, true);
 	return 1;
@@ -4424,36 +4426,51 @@ void __init console_init(void)
  * be a brief interval in which no messages are logged to the console, which
  * makes it difficult to diagnose problems that occur during this time.
  *
- * To mitigate this problem somewhat, only unregister consoles whose memory
- * intersects with the init section. Note that all other boot consoles will
- * get unregistered when the real preferred console is registered.
+ * If a real console has already registered, remove all remaining boot consoles.
+ * Otherwise, mitigate the no-console interval by removing only boot consoles
+ * whose memory intersects with the init section.
  */
 static int __init printk_late_init(void)
 {
+	bool have_real_console = false;
 	struct hlist_node *tmp;
 	struct console *con;
 	int ret;
 
 	console_list_lock();
+	for_each_console(con) {
+		if (!(con->flags & CON_BOOT)) {
+			have_real_console = true;
+			break;
+		}
+	}
+
 	hlist_for_each_entry_safe(con, tmp, &console_list, node) {
 		if (!(con->flags & CON_BOOT))
 			continue;
 
-		/* Check addresses that might be used for enabled consoles. */
-		if (init_section_intersects(con, sizeof(*con)) ||
-		    init_section_contains(con->write, 0) ||
-		    init_section_contains(con->read, 0) ||
-		    init_section_contains(con->device, 0) ||
-		    init_section_contains(con->unblank, 0) ||
-		    init_section_contains(con->data, 0)) {
+		/*
+		 * Keep the boot console when requested or as a fallback
+		 * unless it is using an init section.
+		 */
+		if (keep_bootcon || !have_real_console) {
+			if (!init_section_intersects(con, sizeof(*con)) &&
+			    !init_section_contains(con->write, 0) &&
+			    !init_section_contains(con->read, 0) &&
+			    !init_section_contains(con->device, 0) &&
+			    !init_section_contains(con->unblank, 0) &&
+			    !init_section_contains(con->data, 0))
+				continue;
+
 			/*
 			 * Please, consider moving the reported consoles out
 			 * of the init section.
 			 */
 			pr_warn("bootconsole [%s%d] uses init memory and must be disabled even before the real one is ready\n",
 				con->name, con->index);
-			unregister_console_locked(con);
 		}
+
+		unregister_console_locked(con);
 	}
 	console_list_unlock();
 
@@ -4593,31 +4610,26 @@ bool pr_flush(int timeout_ms, bool reset_on_progress)
 /*
  * Delayed printk version, for scheduler-internal messages:
  */
-#define PRINTK_PENDING_WAKEUP	0x01
-#define PRINTK_PENDING_OUTPUT	0x02
+#define PRINTK_PENDING_OUTPUT	0x01
 
-static DEFINE_PER_CPU(int, printk_pending);
-
-static void wake_up_klogd_work_func(struct irq_work *irq_work)
+static void pending_wake_fn(struct irq_work *irq_work)
 {
-	int pending = this_cpu_xchg(printk_pending, 0);
-
-	if (pending & PRINTK_PENDING_OUTPUT) {
-		if (force_legacy_kthread()) {
-			if (printk_legacy_kthread)
-				wake_up_interruptible(&legacy_wait);
-		} else {
-			if (console_trylock())
-				console_unlock();
-		}
-	}
-
-	if (pending & PRINTK_PENDING_WAKEUP)
-		wake_up_interruptible(&log_wait);
+	wake_up_interruptible(&log_wait);
 }
 
-static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) =
-	IRQ_WORK_INIT_LAZY(wake_up_klogd_work_func);
+static void pending_output_fn(struct irq_work *irq_work)
+{
+	if (force_legacy_kthread()) {
+		if (printk_legacy_kthread)
+			wake_up_interruptible(&legacy_wait);
+	} else {
+		if (console_trylock())
+			console_unlock();
+	}
+}
+
+static struct irq_work pending_wakeup_work = IRQ_WORK_INIT_LAZY(pending_wake_fn);
+static struct irq_work pending_output_work = IRQ_WORK_INIT_LAZY(pending_output_fn);
 
 static void __wake_up_klogd(int val)
 {
@@ -4631,7 +4643,6 @@ static void __wake_up_klogd(int val)
 	if (WARN_ON_ONCE(console_irqwork_blocked))
 		return;
 
-	preempt_disable();
 	/*
 	 * Guarantee any new records can be seen by tasks preparing to wait
 	 * before this context checks if the wait queue is empty.
@@ -4643,12 +4654,11 @@ static void __wake_up_klogd(int val)
 	 *
 	 * This pairs with devkmsg_read:A and syslog_print:A.
 	 */
-	if (wq_has_sleeper(&log_wait) || /* LMM(__wake_up_klogd:A) */
-	    (val & PRINTK_PENDING_OUTPUT)) {
-		this_cpu_or(printk_pending, val);
-		irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
-	}
-	preempt_enable();
+	if (wq_has_sleeper(&log_wait)) /* LMM(__wake_up_klogd:A) */
+		irq_work_queue(&pending_wakeup_work);
+
+	if (val & PRINTK_PENDING_OUTPUT)
+		irq_work_queue(&pending_output_work);
 }
 
 /**
@@ -4663,7 +4673,7 @@ static void __wake_up_klogd(int val)
  */
 void wake_up_klogd(void)
 {
-	__wake_up_klogd(PRINTK_PENDING_WAKEUP);
+	__wake_up_klogd(0);
 }
 
 /**
@@ -4684,7 +4694,7 @@ void defer_console_output(void)
 	 * New messages may have been added directly to the ringbuffer
 	 * using vprintk_store(), so wake any waiters as well.
 	 */
-	__wake_up_klogd(PRINTK_PENDING_WAKEUP | PRINTK_PENDING_OUTPUT);
+	__wake_up_klogd(PRINTK_PENDING_OUTPUT);
 }
 
 /**

kernel/printk/printk_ringbuffer.c

@@ -439,13 +439,12 @@ static enum desc_state get_desc_state(unsigned long id,
 }
 
 /*
- * Get a copy of a specified descriptor and return its queried state. If the
- * descriptor is in an inconsistent state (miss or reserved), the caller can
- * only expect the descriptor's @state_var field to be valid.
+ * Get the state of a specified descriptor.
  *
- * The sequence number and caller_id can be optionally retrieved. Like all
- * non-state_var data, they are only valid if the descriptor is in a
- * consistent state.
+ * Optionally, a copy of the descriptor, sequence number and/or caller ID can
+ * be retrieved. However, (with the exception of @desc_out->state_var) all
+ * retrieved values are invalid if the descriptor is in an inconsistent state
+ * (miss or reserved).
  */
 static enum desc_state desc_read(struct prb_desc_ring *desc_ring,
 				 unsigned long id, struct prb_desc *desc_out,
@@ -1335,7 +1334,6 @@ static struct prb_desc *desc_reopen_last(struct prb_desc_ring *desc_ring,
 {
 	unsigned long prev_state_val;
 	enum desc_state d_state;
-	struct prb_desc desc;
 	struct prb_desc *d;
 	unsigned long id;
 	u32 cid;
@@ -1346,7 +1344,7 @@ static struct prb_desc *desc_reopen_last(struct prb_desc_ring *desc_ring,
 	 * To reduce unnecessarily reopening, first check if the descriptor
 	 * state and caller ID are correct.
 	 */
-	d_state = desc_read(desc_ring, id, &desc, NULL, &cid);
+	d_state = desc_read(desc_ring, id, NULL, NULL, &cid);
 	if (d_state != desc_committed || cid != caller_id)
 		return NULL;
 
@@ -2007,14 +2005,13 @@ u64 prb_first_seq(struct printk_ringbuffer *rb)
 {
 	struct prb_desc_ring *desc_ring = &rb->desc_ring;
 	enum desc_state d_state;
-	struct prb_desc desc;
 	unsigned long id;
 	u64 seq;
 
 	for (;;) {
 		id = atomic_long_read(&rb->desc_ring.tail_id); /* LMM(prb_first_seq:A) */
 
-		d_state = desc_read(desc_ring, id, &desc, &seq, NULL); /* LMM(prb_first_seq:B) */
+		d_state = desc_read(desc_ring, id, NULL, &seq, NULL); /* LMM(prb_first_seq:B) */
 
 		/*
 		 * This loop will not be infinite because the tail is

lib/tests/printf_kunit.c

@@ -876,3 +876,4 @@ kunit_test_suite(printf_test_suite);
 MODULE_AUTHOR("Rasmus Villemoes <linux@rasmusvillemoes.dk>");
 MODULE_DESCRIPTION("Test cases for printf facility");
 MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS("EXPORTED_FOR_KUNIT_TESTING");

lib/vsprintf.c

@@ -25,6 +25,7 @@
 #include <linux/module.h>	/* for KSYM_SYMBOL_LEN */
 #include <linux/types.h>
 #include <linux/string.h>
+#include <linux/string_helpers.h>
 #include <linux/ctype.h>
 #include <linux/hex.h>
 #include <linux/kernel.h>
@@ -54,12 +55,13 @@
 #include <asm/byteorder.h>	/* cpu_to_le16 */
 #include <linux/unaligned.h>
 
-#include <linux/string_helpers.h>
+#include <kunit/visibility.h>
+
 #include "kstrtox.h"
 
 /* Disable pointer hashing if requested */
 bool no_hash_pointers __ro_after_init;
-EXPORT_SYMBOL_FOR_MODULES(no_hash_pointers, "printf_kunit");
+EXPORT_SYMBOL_IF_KUNIT(no_hash_pointers);
 
 /*
  * Hashed pointers policy selected by "hash_pointers=..." boot param
@@ -762,9 +764,8 @@ static int fill_ptr_key(struct notifier_block *nb, unsigned long action, void *d
 {
 	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);
+	/* Pairs with smp_load_acquire() before reading ptr_key. */
+	smp_store_release(&filled_random_ptr_key, true);
 	return NOTIFY_DONE;
 }
 
@@ -781,12 +782,10 @@ static inline int __ptr_to_hashval(const void *ptr, unsigned long *hashval_out)
 {
 	unsigned long hashval;
 
-	if (!READ_ONCE(filled_random_ptr_key))
+	/* Pairs with smp_store_release() after writing ptr_key. */
+	if (!smp_load_acquire(&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);
 	/*
@@ -850,7 +849,7 @@ static char *default_pointer(char *buf, char *end, const void *ptr,
 }
 
 int kptr_restrict __read_mostly;
-EXPORT_SYMBOL_FOR_MODULES(kptr_restrict, "printf_kunit");
+EXPORT_SYMBOL_IF_KUNIT(kptr_restrict);
 
 static noinline_for_stack
 char *restricted_pointer(char *buf, char *end, const void *ptr,