From 8b45503776b6e2c53abbb217970236ed54bd261b Mon Sep 17 00:00:00 2001 From: John Ogness Date: Thu, 25 May 2023 11:37:57 +0206 Subject: [PATCH] serial: 8250: lock port for omap8250_restore_regs() omap8250_restore_regs() accesses UART_IER. This register is modified twice by each console write (serial8250_console_write()) under the port lock. However, not all calls to omap8250_restore_regs() are under the port lock. Add the missing port locking around omap8250_restore_regs() calls. Add lockdep notation to the omap8250_restore_regs(). Note that this is not fixing a real problem because the serial devices are resumed before console printing is enabled. However, adding this locking allows for clean locking semantics for omap8250_restore_regs() so that lockdep can be used to identify possible problems in the future. It also simplifies synchronization of UART_IER in general by not needing to rely on such implementation details. Signed-off-by: John Ogness Link: https://lore.kernel.org/r/20230525093159.223817-7-john.ogness@linutronix.de Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/8250/8250_omap.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c index 3cb9cfa62331c..34939462fd697 100644 --- a/drivers/tty/serial/8250/8250_omap.c +++ b/drivers/tty/serial/8250/8250_omap.c @@ -309,6 +309,9 @@ static void omap8250_restore_regs(struct uart_8250_port *up) struct uart_8250_dma *dma = up->dma; u8 mcr = serial8250_in_MCR(up); + /* Port locked to synchronize UART_IER access against the console. */ + lockdep_assert_held_once(&up->port.lock); + if (dma && dma->tx_running) { /* * TCSANOW requests the change to occur immediately however if @@ -1739,8 +1742,11 @@ static int omap8250_runtime_resume(struct device *dev) if (priv->line >= 0) up = serial8250_get_port(priv->line); - if (up && omap8250_lost_context(up)) + if (up && omap8250_lost_context(up)) { + spin_lock_irq(&up->port.lock); omap8250_restore_regs(up); + spin_unlock_irq(&up->port.lock); + } if (up && up->dma && up->dma->rxchan && !(priv->habit & UART_HAS_EFR2)) { spin_lock_irq(&up->port.lock); -- 2.30.2