[PATCH AUTOSEL 6.4 16/25] serial: cpm_uart: Avoid suspicious locking

Sasha Levin
2023-09-09T00:39:03Z

From: Christophe Leroy <christophe.leroy@csgroup.eu>

[ 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@csgroup.eu>
Link: https://lore.kernel.org/r/f7da5cdc9287960185829cfef681a7d8614efa1f.1691068700.git.christophe.leroy@csgroup.eu
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 349e7da643f01..06232f3b528d2 100644
--- a/drivers/tty/serial/cpm_uart/cpm_uart_core.c
+++ b/drivers/tty/serial/cpm_uart/cpm_uart_core.c
@@ -1255,19 +1255,14 @@ 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