Commit 6cb58cfe authored by John Ogness's avatar John Ogness Committed by Petr Mladek
Browse files

printk: nbcon: Add context to usable() and emit() 



The nbcon consoles will have two callbacks to be used for
different contexts. In order to determine if an nbcon console
is usable, console_is_usable() must know if it is a context
that will need to use the optional write_atomic() callback.
Also, nbcon_emit_next_record() must know which callback it
needs to call.

Add an extra parameter @use_atomic to console_is_usable() and
nbcon_emit_next_record() to specify this.

Since so far only the write_atomic() callback exists,
@use_atomic is set to true for all call sites.

For legacy consoles, @use_atomic is not used.

Signed-off-by: default avatarJohn Ogness <john.ogness@linutronix.de>
Reviewed-by: default avatarPetr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240904120536.115780-5-john.ogness@linutronix.de


Signed-off-by: default avatarPetr Mladek <pmladek@suse.com>
parent 0e53e2d9

kernel/printk/internal.h

+5 −3
Original line number Diff line number Diff line
@@ -97,7 +97,7 @@ bool nbcon_legacy_emit_next_record(struct console *con, bool *handover, 
 * which can also play a role in deciding if @con can be used to print

 * records.

 */

static inline bool console_is_usable(struct console *con, short flags)

static inline bool console_is_usable(struct console *con, short flags, bool use_atomic)

{

	if (!(flags & CON_ENABLED))

		return false;
@@ -106,7 +106,8 @@ static inline bool console_is_usable(struct console *con, short flags) 
		return false;



	if (flags & CON_NBCON) {

		if (!con->write_atomic)

		/* The write_atomic() callback is optional. */

		if (use_atomic && !con->write_atomic)

			return false;

	} else {

		if (!con->write)
@@ -149,7 +150,8 @@ static inline void nbcon_atomic_flush_pending(void) { } 
static inline bool nbcon_legacy_emit_next_record(struct console *con, bool *handover,

						 int cookie) { return false; }



static inline bool console_is_usable(struct console *con, short flags) { return false; }

static inline bool console_is_usable(struct console *con, short flags,

				     bool use_atomic) { return false; }



#endif /* CONFIG_PRINTK */

kernel/printk/nbcon.c

+19 −15
Original line number Diff line number Diff line
@@ -922,6 +922,7 @@ EXPORT_SYMBOL_GPL(nbcon_reacquire_nobuf); 
/**

 * nbcon_emit_next_record - Emit a record in the acquired context

 * @wctxt:	The write context that will be handed to the write function

 * @use_atomic:	True if the write_atomic() callback is to be used

 *

 * Return:	True if this context still owns the console. False if

 *		ownership was handed over or taken.
@@ -935,7 +936,7 @@ EXPORT_SYMBOL_GPL(nbcon_reacquire_nobuf); 
 * When true is returned, @wctxt->ctxt.backlog indicates whether there are

 * still records pending in the ringbuffer,

 */

static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt)

static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt, bool use_atomic)

{

	struct nbcon_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt);

	struct console *con = ctxt->console;
@@ -946,6 +947,18 @@ static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt) 
	unsigned long con_dropped;

	unsigned long dropped;



	/*

	 * This function should never be called for consoles that have not

	 * implemented the necessary callback for writing: i.e. legacy

	 * consoles and, when atomic, nbcon consoles with no write_atomic().

	 * Handle it as if ownership was lost and try to continue.

	 */

	if (WARN_ON_ONCE((use_atomic && !con->write_atomic) ||

			 !(console_srcu_read_flags(con) & CON_NBCON))) {

		nbcon_context_release(ctxt);

		return false;

	}



	/*

	 * The printk buffers are filled within an unsafe section. This

	 * prevents NBCON_PRIO_NORMAL and NBCON_PRIO_EMERGENCY from
@@ -980,17 +993,8 @@ static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt) 
	/* Initialize the write context for driver callbacks. */

	nbcon_write_context_set_buf(wctxt, &pmsg.pbufs->outbuf[0], pmsg.outbuf_len);



	if (con->write_atomic) {

	if (use_atomic)

		con->write_atomic(con, wctxt);

	} else {

		/*

		 * This function should never be called for legacy consoles.

		 * Handle it as if ownership was lost and try to continue.

		 */

		WARN_ON_ONCE(1);

		nbcon_context_release(ctxt);

		return false;

	}



	if (!wctxt->outbuf) {

		/*
@@ -1118,7 +1122,7 @@ static bool nbcon_atomic_emit_one(struct nbcon_write_context *wctxt) 
	 * The higher priority printing context takes over responsibility

	 * to print the pending records.

	 */

	if (!nbcon_emit_next_record(wctxt))

	if (!nbcon_emit_next_record(wctxt, true))

		return false;



	nbcon_context_release(ctxt);
@@ -1219,7 +1223,7 @@ static int __nbcon_atomic_flush_pending_con(struct console *con, u64 stop_seq, 
		 * handed over or taken over. In both cases the context is no

		 * longer valid.

		 */

		if (!nbcon_emit_next_record(&wctxt))

		if (!nbcon_emit_next_record(&wctxt, true))

			return -EAGAIN;



		if (!ctxt->backlog) {
@@ -1305,7 +1309,7 @@ static void __nbcon_atomic_flush_pending(u64 stop_seq, bool allow_unsafe_takeove 
		if (!(flags & CON_NBCON))

			continue;



		if (!console_is_usable(con, flags))

		if (!console_is_usable(con, flags, true))

			continue;



		if (nbcon_seq_read(con) >= stop_seq)
@@ -1490,7 +1494,7 @@ void nbcon_device_release(struct console *con) 
	 * the console is usable throughout flushing.

	 */

	cookie = console_srcu_read_lock();

	if (console_is_usable(con, console_srcu_read_flags(con)) &&

	if (console_is_usable(con, console_srcu_read_flags(con), true) &&

	    prb_read_valid(prb, nbcon_seq_read(con), NULL)) {

		/*

		 * If nbcon_atomic flushing is not available, fallback to

kernel/printk/printk.c

+3 −3
Original line number Diff line number Diff line
@@ -3071,7 +3071,7 @@ static bool console_flush_all(bool do_cond_resched, u64 *next_seq, bool *handove 
			u64 printk_seq;

			bool progress;



			if (!console_is_usable(con, flags))

			if (!console_is_usable(con, flags, true))

				continue;

			any_usable = true;
@@ -3773,7 +3773,7 @@ static int unregister_console_locked(struct console *console) 


	if (!console_is_registered_locked(console))

		res = -ENODEV;

	else if (console_is_usable(console, console->flags))

	else if (console_is_usable(console, console->flags, true))

		__pr_flush(console, 1000, true);



	/* Disable it unconditionally */
@@ -4043,7 +4043,7 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre 
			 * that they make forward progress, so only increment

			 * @diff for usable consoles.

			 */

			if (!console_is_usable(c, flags))

			if (!console_is_usable(c, flags, true))

				continue;



			if (flags & CON_NBCON) {