Merge tag 'printk-for-6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux

Pull printk updates from Petr Mladek:

 - Another preparation step for introducing printk kthreads. The main
   piece is a per-console lock with several features:

    - Support three priorities: normal, emergency, and panic. They will
      be defined by a context where the lock is taken. A context with a
      higher priority is allowed to take over the lock from a context
      with a lower one.

      The plan is to use the emergency context for Oops and WARN()
      messages, and also by watchdogs.

      The panic() context will be used on panic CPU.

    - The owner might enter/exit regions where it is not safe to take
      over the lock. It allows the take over the lock a safe way in the
      middle of a message.

      For example, serial drivers emit characters one by one. And the
      serial port is in a safe state in between.

      Only the final console_flush_in_panic() will be allowed to take
      over the lock even in the unsafe state (last chance, pray, and
      hope).

    - A higher priority context might busy wait with a timeout. The
      current owner is informed about the waiter and releases the lock
      on exit from the unsafe state.

    - The new lock is safe even in atomic contexts, including NMI.

   Another change is a safe manipulation of per-console sequence number
   counter under the new lock.

 - simple_strntoull() micro-optimization

 - Reduce pr_flush() pooling time.

 - Calm down false warning about possible buffer invalid access to
   console buffers when CONFIG_PRINTK is disabled.

[ .. and Thomas Gleixner wants to point out that while several of the
  commits are attributed to him, he only authored the early versions of
  said commits, and that John Ogness and Petr Mladek have been the ones
  who sorted out the details and really should be those who get the
  credit   - Linus ]

* tag 'printk-for-6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
  vsprintf: uninline simple_strntoull(), reorder arguments
  printk: printk: Remove unnecessary statements＇len = 0;＇
  printk: Reduce pr_flush() pooling time
  printk: fix illegal pbufs access for !CONFIG_PRINTK
  printk: nbcon: Allow drivers to mark unsafe regions and check state
  printk: nbcon: Add emit function and callback function for atomic printing
  printk: nbcon: Add sequence handling
  printk: nbcon: Add ownership state functions
  printk: nbcon: Add buffer management
  printk: Make static printk buffers available to nbcon
  printk: nbcon: Add acquire/release logic
  printk: Add non-BKL (nbcon) console basic infrastructure

1 files changed, 31 insertions, 0 deletions

diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h
index 7d4979d5c3ce..6c2afee5ef62 100644
--- a/kernel/printk/internal.h
+++ b/kernel/printk/internal.h
@@ -3,6 +3,8 @@
  * internal.h - printk internal definitions
  */
 #include <linux/percpu.h>
+#include <linux/console.h>
+#include "printk_ringbuffer.h"
 
 #if defined(CONFIG_PRINTK) && defined(CONFIG_SYSCTL)
 void __init printk_sysctl_init(void);
@@ -12,6 +14,12 @@ int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write,
 #define printk_sysctl_init() do { } while (0)
 #endif
 
+#define con_printk(lvl, con, fmt, ...)				\
+	printk(lvl pr_fmt("%s%sconsole [%s%d] " fmt),		\
+		(con->flags & CON_NBCON) ? "" : "legacy ",	\
+		(con->flags & CON_BOOT) ? "boot" : "",		\
+		con->name, con->index, ##__VA_ARGS__)
+
 #ifdef CONFIG_PRINTK
 
 #ifdef CONFIG_PRINTK_CALLER
@@ -35,6 +43,8 @@ enum printk_info_flags {
 	LOG_CONT	= 8,	/* text is a fragment of a continuation line */
 };
 
+extern struct printk_ringbuffer *prb;
+
 __printf(4, 0)
 int vprintk_store(int facility, int level,
 		  const struct dev_printk_info *dev_info,
@@ -61,6 +71,13 @@ void defer_console_output(void);
 
 u16 printk_parse_prefix(const char *text, int *level,
 			enum printk_info_flags *flags);
+
+u64 nbcon_seq_read(struct console *con);
+void nbcon_seq_force(struct console *con, u64 seq);
+bool nbcon_alloc(struct console *con);
+void nbcon_init(struct console *con);
+void nbcon_free(struct console *con);
+
 #else
 
 #define PRINTK_PREFIX_MAX	0
@@ -76,8 +93,16 @@ u16 printk_parse_prefix(const char *text, int *level,
 #define printk_safe_exit_irqrestore(flags) local_irq_restore(flags)
 
 static inline bool printk_percpu_data_ready(void) { return false; }
+static inline u64 nbcon_seq_read(struct console *con) { return 0; }
+static inline void nbcon_seq_force(struct console *con, u64 seq) { }
+static inline bool nbcon_alloc(struct console *con) { return false; }
+static inline void nbcon_init(struct console *con) { }
+static inline void nbcon_free(struct console *con) { }
+
 #endif /* CONFIG_PRINTK */
 
+extern struct printk_buffers printk_shared_pbufs;
+
 /**
  * struct printk_buffers - Buffers to read/format/output printk messages.
  * @outbuf:	After formatting, contains text to output.
@@ -105,3 +130,9 @@ struct printk_message {
 };
 
 bool other_cpu_in_panic(void);
+bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
+			     bool is_extended, bool may_supress);
+
+#ifdef CONFIG_PRINTK
+void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped);
+#endif