Merge tag 'printk-for-4.19' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk

Pull printk updates from Petr Mladek:

 - Different vendors have a different expectation about a console
   quietness. Make it configurable to reduce bike-shedding about the
   upstream default

 - Decide about the message visibility when the message is stored. It
   avoids races caused by a delayed console handling

 - Always store printk() messages into the per-CPU buffers again in NMI.
   The only exception is when flushing trace log in panic(). There the
   risk of loosing messages is worth an eventual reordering

 - Handle invalid %pO printf modifiers correctly

 - Better handle %p printf modifier tests before crng is initialized

 - Some clean up

* tag 'printk-for-4.19' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk:
  lib/vsprintf: Do not handle %pO[^F] as %px
  printk: Fix warning about unused suppress_message_printing
  printk/nmi: Prevent deadlock when accessing the main log buffer in NMI
  printk: Create helper function to queue deferred console handling
  printk: Split the code for storing a message into the log buffer
  printk: Clean up syslog_print_all()
  printk: Remove unnecessary kmalloc() from syslog during clear
  printk: Make CONSOLE_LOGLEVEL_QUIET configurable
  printk: make sure to print log on console.
  lib/test_printf.c: accept "ptrval" as valid result for plain 'p' tests

lib/Kconfig.debug

@@ -30,6 +30,17 @@ config CONSOLE_LOGLEVEL_DEFAULT
 	  usage in the kernel. That is controlled by the MESSAGE_LOGLEVEL_DEFAULT
 	  option.
 
+config CONSOLE_LOGLEVEL_QUIET
+	int "quiet console loglevel (1-15)"
+	range 1 15
+	default "4"
+	help
+	  loglevel to use when "quiet" is passed on the kernel commandline.
+
+	  When "quiet" is passed on the kernel commandline this loglevel
+	  will be used as the loglevel. IOW passing "quiet" will be the
+	  equivalent of passing "loglevel=<CONSOLE_LOGLEVEL_QUIET>"
+
 config MESSAGE_LOGLEVEL_DEFAULT
 	int "Default message log level (1-7)"
 	range 1 7

lib/nmi_backtrace.c

@@ -87,11 +87,9 @@ void nmi_trigger_cpumask_backtrace(const cpumask_t *mask,
 
 bool nmi_cpu_backtrace(struct pt_regs *regs)
 {
-	static arch_spinlock_t lock = __ARCH_SPIN_LOCK_UNLOCKED;
 	int cpu = smp_processor_id();
 
 	if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
-		arch_spin_lock(&lock);
 		if (regs && cpu_in_idle(instruction_pointer(regs))) {
 			pr_warn("NMI backtrace for cpu %d skipped: idling at %pS\n",
 				cpu, (void *)instruction_pointer(regs));
@@ -102,7 +100,6 @@ bool nmi_cpu_backtrace(struct pt_regs *regs)
 			else
 				dump_stack();
 		}
-		arch_spin_unlock(&lock);
 		cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
 		return true;
 	}

lib/test_printf.c

@@ -206,6 +206,7 @@ test_string(void)
 #define PTR_WIDTH 16
 #define PTR ((void *)0xffff0123456789abUL)
 #define PTR_STR "ffff0123456789ab"
+#define PTR_VAL_NO_CRNG "(____ptrval____)"
 #define ZEROS "00000000"	/* hex 32 zero bits */
 
 static int __init
@@ -216,7 +217,16 @@ plain_format(void)
 
 	nchars = snprintf(buf, PLAIN_BUF_SIZE, "%p", PTR);
 
-	if (nchars != PTR_WIDTH || strncmp(buf, ZEROS, strlen(ZEROS)) != 0)
+	if (nchars != PTR_WIDTH)
+		return -1;
+
+	if (strncmp(buf, PTR_VAL_NO_CRNG, PTR_WIDTH) == 0) {
+		pr_warn("crng possibly not yet initialized. plain 'p' buffer contains \"%s\"",
+			PTR_VAL_NO_CRNG);
+		return 0;
+	}
+
+	if (strncmp(buf, ZEROS, strlen(ZEROS)) != 0)
 		return -1;
 
 	return 0;
@@ -227,6 +237,7 @@ plain_format(void)
 #define PTR_WIDTH 8
 #define PTR ((void *)0x456789ab)
 #define PTR_STR "456789ab"
+#define PTR_VAL_NO_CRNG "(ptrval)"
 
 static int __init
 plain_format(void)
@@ -245,7 +256,16 @@ plain_hash(void)
 
 	nchars = snprintf(buf, PLAIN_BUF_SIZE, "%p", PTR);
 
-	if (nchars != PTR_WIDTH || strncmp(buf, PTR_STR, PTR_WIDTH) == 0)
+	if (nchars != PTR_WIDTH)
+		return -1;
+
+	if (strncmp(buf, PTR_VAL_NO_CRNG, PTR_WIDTH) == 0) {
+		pr_warn("crng possibly not yet initialized. plain 'p' buffer contains \"%s\"",
+			PTR_VAL_NO_CRNG);
+		return 0;
+	}
+
+	if (strncmp(buf, PTR_STR, PTR_WIDTH) == 0)
 		return -1;
 
 	return 0;

lib/vsprintf.c

@@ -1942,6 +1942,7 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
 		case 'F':
 			return device_node_string(buf, end, ptr, spec, fmt + 1);
 		}
+		break;
 	case 'x':
 		return pointer_string(buf, end, ptr, spec);
 	}