Merge: Update printk to latest v6.12 longterm

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-10/-/merge_requests/848

JIRA: https://issues.redhat.com/browse/RHEL-89498

This backport updates the printk (and serial 8250) subsytem in C10s/10.1 to properly reflect what exists in the most recent linux longterm kernels.

Additionally, a small patch to make `pr_flush` a public function, permitting the proper flushing of console log buffers on shutdown, has also been pulled in.

Signed-off-by: Derek Barbosa <debarbos@redhat.com>

Approved-by: Herton R. Krzesinski <herton@redhat.com>
Approved-by: Eder Zulian <ezulian@redhat.com>
Approved-by: Gabriele Monaco <gmonaco@redhat.com>
Approved-by: Rafael Aquini <raquini@redhat.com>
Approved-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: CKI GitLab Kmaint Pipeline Bot <26919896-cki-kmaint-pipeline-bot@users.noreply.gitlab.com>

Author: CKI KWF Bot

drivers/tty/serial/8250/8250.h

@@ -374,6 +374,7 @@ static inline int is_omap1510_8250(struct uart_8250_port *pt)
 
 #ifdef CONFIG_SERIAL_8250_DMA
 extern int serial8250_tx_dma(struct uart_8250_port *);
+extern void serial8250_tx_dma_flush(struct uart_8250_port *);
 extern int serial8250_rx_dma(struct uart_8250_port *);
 extern void serial8250_rx_dma_flush(struct uart_8250_port *);
 extern int serial8250_request_dma(struct uart_8250_port *);
@@ -406,6 +407,7 @@ static inline int serial8250_tx_dma(struct uart_8250_port *p)
 {
 	return -1;
 }
+static inline void serial8250_tx_dma_flush(struct uart_8250_port *p) { }
 static inline int serial8250_rx_dma(struct uart_8250_port *p)
 {
 	return -1;

drivers/tty/serial/8250/8250_core.c

@@ -812,6 +812,9 @@ int serial8250_register_8250_port(const struct uart_8250_port *up)
 			uart->dl_write = up->dl_write;
 
 		if (uart->port.type != PORT_8250_CIR) {
+			if (uart_console_registered(&uart->port))
+				pm_runtime_get_sync(uart->port.dev);
+
 			if (serial8250_isa_config != NULL)
 				serial8250_isa_config(0, &uart->port,
 						&uart->capabilities);

drivers/tty/serial/8250/8250_dma.c

@@ -149,6 +149,22 @@ int serial8250_tx_dma(struct uart_8250_port *p)
 	return ret;
 }
 
+void serial8250_tx_dma_flush(struct uart_8250_port *p)
+{
+	struct uart_8250_dma *dma = p->dma;
+
+	if (!dma->tx_running)
+		return;
+
+	/*
+	 * kfifo_reset() has been called by the serial core, avoid
+	 * advancing and underflowing in __dma_tx_complete().
+	 */
+	dma->tx_size = 0;
+
+	dmaengine_terminate_async(dma->txchan);
+}
+
 int serial8250_rx_dma(struct uart_8250_port *p)
 {
 	struct uart_8250_dma		*dma = p->dma;

drivers/tty/serial/8250/8250_port.c

@@ -2523,6 +2523,14 @@ static void serial8250_shutdown(struct uart_port *port)
 		serial8250_do_shutdown(port);
 }
 
+static void serial8250_flush_buffer(struct uart_port *port)
+{
+	struct uart_8250_port *up = up_to_u8250p(port);
+
+	if (up->dma)
+		serial8250_tx_dma_flush(up);
+}
+
 static unsigned int serial8250_do_get_divisor(struct uart_port *port,
 					      unsigned int baud,
 					      unsigned int *frac)
@@ -3206,6 +3214,7 @@ static const struct uart_ops serial8250_pops = {
 	.break_ctl	= serial8250_break_ctl,
 	.startup	= serial8250_startup,
 	.shutdown	= serial8250_shutdown,
+	.flush_buffer	= serial8250_flush_buffer,
 	.set_termios	= serial8250_set_termios,
 	.set_ldisc	= serial8250_set_ldisc,
 	.pm		= serial8250_pm,

include/linux/printk.h

@@ -204,6 +204,7 @@ void printk_legacy_allow_panic_sync(void);
 extern bool nbcon_device_try_acquire(struct console *con);
 extern void nbcon_device_release(struct console *con);
 void nbcon_atomic_flush_unsafe(void);
+bool pr_flush(int timeout_ms, bool reset_on_progress);
 #else
 static inline __printf(1, 0)
 int vprintk(const char *s, va_list args)
@@ -304,6 +305,11 @@ static inline void nbcon_atomic_flush_unsafe(void)
 {
 }
 
+static inline bool pr_flush(int timeout_ms, bool reset_on_progress)
+{
+	return true;
+}
+
 #endif
 
 bool this_cpu_in_panic(void);

kernel/printk/internal.h

@@ -335,3 +335,9 @@ bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
 void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped);
 void console_prepend_replay(struct printk_message *pmsg);
 #endif
+
+#ifdef CONFIG_SMP
+bool is_printk_cpu_sync_owner(void);
+#else
+static inline bool is_printk_cpu_sync_owner(void) { return false; }
+#endif

kernel/printk/printk.c

@@ -523,7 +523,7 @@ static struct latched_seq clear_seq = {
 /* record buffer */
 #define LOG_ALIGN __alignof__(unsigned long)
 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
-#define LOG_BUF_LEN_MAX (u32)(1 << 31)
+#define LOG_BUF_LEN_MAX ((u32)1 << 31)
 static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
 static char *log_buf = __log_buf;
 static u32 log_buf_len = __LOG_BUF_LEN;
@@ -2436,7 +2436,6 @@ asmlinkage __visible int _printk(const char *fmt, ...)
 }
 EXPORT_SYMBOL(_printk);
 
-static bool pr_flush(int timeout_ms, bool reset_on_progress);
 static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress);
 
 #else /* CONFIG_PRINTK */
@@ -2449,7 +2448,6 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre
 
 static u64 syslog_seq;
 
-static bool pr_flush(int timeout_ms, bool reset_on_progress) { return true; }
 static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progress) { return true; }
 
 #endif /* CONFIG_PRINTK */
@@ -4436,7 +4434,7 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre
  * Context: Process context. May sleep while acquiring console lock.
  * Return: true if all usable printers are caught up.
  */
-static bool pr_flush(int timeout_ms, bool reset_on_progress)
+bool pr_flush(int timeout_ms, bool reset_on_progress)
 {
 	return __pr_flush(NULL, timeout_ms, reset_on_progress);
 }
@@ -4892,6 +4890,11 @@ void console_try_replay_all(void)
 static atomic_t printk_cpu_sync_owner = ATOMIC_INIT(-1);
 static atomic_t printk_cpu_sync_nested = ATOMIC_INIT(0);
 
+bool is_printk_cpu_sync_owner(void)
+{
+	return (atomic_read(&printk_cpu_sync_owner) == raw_smp_processor_id());
+}
+
 /**
  * __printk_cpu_sync_wait() - Busy wait until the printk cpu-reentrant
  *                            spinning lock is not owned by any CPU.

kernel/printk/printk_safe.c

@@ -43,10 +43,15 @@ bool is_printk_legacy_deferred(void)
 	/*
 	 * The per-CPU variable @printk_context can be read safely in any
 	 * context. CPU migration is always disabled when set.
+	 *
+	 * A context holding the printk_cpu_sync must not spin waiting for
+	 * another CPU. For legacy printing, it could be the console_lock
+	 * or the port lock.
 	 */
 	return (force_legacy_kthread() ||
 		this_cpu_read(printk_context) ||
-		in_nmi());
+		in_nmi() ||
+		is_printk_cpu_sync_owner());
 }
 
 asmlinkage int vprintk(const char *fmt, va_list args)

kernel/reboot.c

@@ -697,6 +697,7 @@ void kernel_power_off(void)
 	migrate_to_reboot_cpu();
 	syscore_shutdown();
 	pr_emerg("Power down\n");
+	pr_flush(1000, true);
 	kmsg_dump(KMSG_DUMP_SHUTDOWN);
 	machine_power_off();
 }