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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: linux-serial@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Jiri Slaby <jirislaby@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Russell King <linux@armlinux.org.uk>
Subject: [PATCH 01/18] serial: amba-pl011: Use uart_prepare_sysrq_char().
Date: Fri,  1 Mar 2024 22:45:14 +0100	[thread overview]
Message-ID: <20240301215246.891055-2-bigeasy@linutronix.de> (raw)
In-Reply-To: <20240301215246.891055-1-bigeasy@linutronix.de>

The port lock is a spinlock_t which is becomes a sleeping lock on PREEMPT_RT.
The driver splits the locking function into two parts: local_irq_save() and
uart_port_lock() and this breaks PREEMPT_RT.

Delay handling sysrq until port lock is dropped.
Remove the special case in the console write routine an always use the
complete locking function.

Cc: Russell King <linux@armlinux.org.uk>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 drivers/tty/serial/amba-pl011.c | 24 ++++++++----------------
 1 file changed, 8 insertions(+), 16 deletions(-)

diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index cf2c890a560f0..2fa3fb30dc6c7 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -348,10 +348,7 @@ static int pl011_fifo_to_tty(struct uart_amba_port *uap)
 				flag = TTY_FRAME;
 		}
 
-		uart_port_unlock(&uap->port);
-		sysrq = uart_handle_sysrq_char(&uap->port, ch & 255);
-		uart_port_lock(&uap->port);
-
+		sysrq = uart_prepare_sysrq_char(&uap->port, ch & 255);
 		if (!sysrq)
 			uart_insert_char(&uap->port, ch, UART011_DR_OE, ch, flag);
 	}
@@ -1017,7 +1014,7 @@ static void pl011_dma_rx_callback(void *data)
 	ret = pl011_dma_rx_trigger_dma(uap);
 
 	pl011_dma_rx_chars(uap, pending, lastbuf, false);
-	uart_port_unlock_irq(&uap->port);
+	uart_unlock_and_check_sysrq(&uap->port);
 	/*
 	 * Do this check after we picked the DMA chars so we don't
 	 * get some IRQ immediately from RX.
@@ -1540,11 +1537,10 @@ static void check_apply_cts_event_workaround(struct uart_amba_port *uap)
 static irqreturn_t pl011_int(int irq, void *dev_id)
 {
 	struct uart_amba_port *uap = dev_id;
-	unsigned long flags;
 	unsigned int status, pass_counter = AMBA_ISR_PASS_LIMIT;
 	int handled = 0;
 
-	uart_port_lock_irqsave(&uap->port, &flags);
+	uart_port_lock(&uap->port);
 	status = pl011_read(uap, REG_RIS) & uap->im;
 	if (status) {
 		do {
@@ -1573,7 +1569,7 @@ static irqreturn_t pl011_int(int irq, void *dev_id)
 		handled = 1;
 	}
 
-	uart_port_unlock_irqrestore(&uap->port, flags);
+	uart_unlock_and_check_sysrq(&uap->port);
 
 	return IRQ_RETVAL(handled);
 }
@@ -2322,13 +2318,10 @@ pl011_console_write(struct console *co, const char *s, unsigned int count)
 
 	clk_enable(uap->clk);
 
-	local_irq_save(flags);
-	if (uap->port.sysrq)
-		locked = 0;
-	else if (oops_in_progress)
-		locked = uart_port_trylock(&uap->port);
+	if (oops_in_progress)
+		locked = uart_port_trylock_irqsave(&uap->port, &flags);
 	else
-		uart_port_lock(&uap->port);
+		uart_port_lock_irqsave(&uap->port, &flags);
 
 	/*
 	 *	First save the CR then disable the interrupts
@@ -2354,8 +2347,7 @@ pl011_console_write(struct console *co, const char *s, unsigned int count)
 		pl011_write(old_cr, uap, REG_CR);
 
 	if (locked)
-		uart_port_unlock(&uap->port);
-	local_irq_restore(flags);
+		uart_port_unlock_irqrestore(&uap->port, flags);
 
 	clk_disable(uap->clk);
 }
-- 
2.43.0


  reply	other threads:[~2024-03-01 21:52 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-03-01 21:45 [PATCH 00/18] serial: Use uart_prepare_sysrq_char() Sebastian Andrzej Siewior
2024-03-01 21:45 ` Sebastian Andrzej Siewior [this message]
2024-03-01 21:45 ` [PATCH 02/18] serial: ar933x: " Sebastian Andrzej Siewior
2024-03-01 21:45 ` [PATCH 03/18] serial: bcm63xx: " Sebastian Andrzej Siewior
2024-03-01 21:45 ` [PATCH 04/18] serial: meson: " Sebastian Andrzej Siewior
2024-03-01 21:45   ` Sebastian Andrzej Siewior
2024-03-01 21:45   ` Sebastian Andrzej Siewior
2024-03-01 21:45 ` [PATCH 05/18] serial: msm: " Sebastian Andrzej Siewior
2024-03-01 21:45 ` [PATCH 06/18] serial: omap: " Sebastian Andrzej Siewior
2024-03-01 21:45 ` [PATCH 07/18] serial: pxa: " Sebastian Andrzej Siewior
2024-03-01 21:45 ` [PATCH 08/18] serial: sunplus: " Sebastian Andrzej Siewior
2024-03-01 21:45 ` [PATCH 09/18] serial: lpc32xx_hs: Use uart_prepare_sysrq_char() to handle sysrq Sebastian Andrzej Siewior
2024-03-01 21:45   ` Sebastian Andrzej Siewior
2024-03-01 21:45 ` [PATCH 10/18] serial: owl: " Sebastian Andrzej Siewior
2024-03-01 21:45   ` Sebastian Andrzej Siewior
2024-03-01 21:45 ` [PATCH 11/18] serial: rda: " Sebastian Andrzej Siewior
2024-03-01 21:45   ` Sebastian Andrzej Siewior
2024-03-01 21:45 ` [PATCH 12/18] serial: sifive: " Sebastian Andrzej Siewior
2024-03-01 21:45   ` Sebastian Andrzej Siewior
2024-03-07  1:39   ` Samuel Holland
2024-03-07  1:39     ` Samuel Holland
2024-03-01 21:45 ` [PATCH 13/18] serial: pch: Invoke handle_rx_to() directly Sebastian Andrzej Siewior
2024-03-01 21:45 ` [PATCH 14/18] serial: pch: Make push_rx() return void Sebastian Andrzej Siewior
2024-03-01 21:45 ` [PATCH 15/18] serial: pch: Don't disable interrupts while acquiring lock in ISR Sebastian Andrzej Siewior
2024-03-01 21:45 ` [PATCH 16/18] serial: pch: Don't initialize uart_port's spin_lock Sebastian Andrzej Siewior
2024-03-01 21:45 ` [PATCH 17/18] serial: pch: Remove eg20t_port::lock Sebastian Andrzej Siewior
2024-03-01 21:45 ` [PATCH 18/18] serial: pch: Use uart_prepare_sysrq_char() Sebastian Andrzej Siewior

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