Commit 8ba77712 authored by John Ogness's avatar John Ogness Committed by Petr Mladek
Browse files

printk: nbcon: Flush new records on device_release() 



There may be new records that were added while a driver was
holding the nbcon context for non-printing purposes. These
new records must be flushed by the nbcon_device_release()
context because no other context will do it.

If boot consoles are registered, the legacy loop is used
(either direct or per irq_work) to handle the flushing.

Signed-off-by: default avatarJohn Ogness <john.ogness@linutronix.de>
Reviewed-by: default avatarPetr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-25-john.ogness@linutronix.de


Signed-off-by: default avatarPetr Mladek <pmladek@suse.com>
parent 70411bf8

kernel/printk/internal.h

+2 −0
Original line number Diff line number Diff line
@@ -153,6 +153,8 @@ static inline bool console_is_usable(struct console *con, short flags) { return 


#endif /* CONFIG_PRINTK */



extern bool have_boot_console;



extern struct printk_buffers printk_shared_pbufs;



/**

kernel/printk/nbcon.c

+20 −0
Original line number Diff line number Diff line
@@ -1326,10 +1326,30 @@ EXPORT_SYMBOL_GPL(nbcon_device_try_acquire); 
void nbcon_device_release(struct console *con)

{

	struct nbcon_context *ctxt = &ACCESS_PRIVATE(con, nbcon_device_ctxt);

	int cookie;



	if (!nbcon_context_exit_unsafe(ctxt))

		return;



	nbcon_context_release(ctxt);



	/*

	 * This context must flush any new records added while the console

	 * was locked. The console_srcu_read_lock must be taken to ensure

	 * the console is usable throughout flushing.

	 */

	cookie = console_srcu_read_lock();

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

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

		if (!have_boot_console) {

			__nbcon_atomic_flush_pending_con(con, prb_next_reserve_seq(prb));

		} else if (!is_printk_legacy_deferred()) {

			if (console_trylock())

				console_unlock();

		} else {

			printk_trigger_flush();

		}

	}

	console_srcu_read_unlock(cookie);

}

EXPORT_SYMBOL_GPL(nbcon_device_release);

kernel/printk/printk.c

+1 −1
Original line number Diff line number Diff line
@@ -469,7 +469,7 @@ static DEFINE_MUTEX(syslog_lock); 
 * the console lock. This is because boot consoles and nbcon consoles may

 * have mapped the same hardware.

 */

static bool have_boot_console;

bool have_boot_console;



#ifdef CONFIG_PRINTK

DECLARE_WAIT_QUEUE_HEAD(log_wait);