[PATCH 5.4 343/367] serial: cpm_uart: Avoid suspicious locking

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

5.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Christophe Leroy <christophe.leroy@xxxxxxxxxx>

[ Upstream commit 36ef11d311f405e55ad8e848c19b212ff71ef536 ]

  CHECK   drivers/tty/serial/cpm_uart/cpm_uart_core.c
drivers/tty/serial/cpm_uart/cpm_uart_core.c:1271:39: warning: context imbalance in 'cpm_uart_console_write' - unexpected unlock

Allthough 'nolock' is not expected to change, sparse find the following
form suspicious:

	if (unlikely(nolock)) {
		local_irq_save(flags);
	} else {
		spin_lock_irqsave(&pinfo->port.lock, flags);
	}

	cpm_uart_early_write(pinfo, s, count, true);

	if (unlikely(nolock)) {
		local_irq_restore(flags);
	} else {
		spin_unlock_irqrestore(&pinfo->port.lock, flags);
	}

Rewrite it a more obvious form:

	if (unlikely(oops_in_progress)) {
		local_irq_save(flags);
		cpm_uart_early_write(pinfo, s, count, true);
		local_irq_restore(flags);
	} else {
		spin_lock_irqsave(&pinfo->port.lock, flags);
		cpm_uart_early_write(pinfo, s, count, true);
		spin_unlock_irqrestore(&pinfo->port.lock, flags);
	}

Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Link: https://lore.kernel.org/r/f7da5cdc9287960185829cfef681a7d8614efa1f.1691068700.git.christophe.leroy@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/tty/serial/cpm_uart/cpm_uart_core.c | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/drivers/tty/serial/cpm_uart/cpm_uart_core.c b/drivers/tty/serial/cpm_uart/cpm_uart_core.c
index de6d02f7abe2b..c37036fee231d 100644
--- a/drivers/tty/serial/cpm_uart/cpm_uart_core.c
+++ b/drivers/tty/serial/cpm_uart/cpm_uart_core.c
@@ -1267,19 +1267,14 @@ static void cpm_uart_console_write(struct console *co, const char *s,
 {
 	struct uart_cpm_port *pinfo = &cpm_uart_ports[co->index];
 	unsigned long flags;
-	int nolock = oops_in_progress;
 
-	if (unlikely(nolock)) {
+	if (unlikely(oops_in_progress)) {
 		local_irq_save(flags);
-	} else {
-		spin_lock_irqsave(&pinfo->port.lock, flags);
-	}
-
-	cpm_uart_early_write(pinfo, s, count, true);
-
-	if (unlikely(nolock)) {
+		cpm_uart_early_write(pinfo, s, count, true);
 		local_irq_restore(flags);
 	} else {
+		spin_lock_irqsave(&pinfo->port.lock, flags);
+		cpm_uart_early_write(pinfo, s, count, true);
 		spin_unlock_irqrestore(&pinfo->port.lock, flags);
 	}
 }
-- 
2.40.1