diff options
| author | Sean Anderson <sean.anderson@linux.dev> | 2025-01-11 00:38:22 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-02-17 11:40:43 +0300 |
| commit | 8ea0e7b3d7b8f2f0fc9db491ff22a0abe120801c (patch) | |
| tree | 97f544c9ee8a80ed438be6557a42c538f16b30c2 /drivers/tty/serial | |
| parent | d113f9723f2bfd9c6feeb899b8ddbee6b8a6e01f (diff) | |
| download | linux-8ea0e7b3d7b8f2f0fc9db491ff22a0abe120801c.tar.xz | |
tty: xilinx_uartps: split sysrq handling
commit b06f388994500297bb91be60ffaf6825ecfd2afe upstream.
lockdep detects the following circular locking dependency:
CPU 0 CPU 1
========================== ============================
cdns_uart_isr() printk()
uart_port_lock(port) console_lock()
cdns_uart_console_write()
if (!port->sysrq)
uart_port_lock(port)
uart_handle_break()
port->sysrq = ...
uart_handle_sysrq_char()
printk()
console_lock()
The fixed commit attempts to avoid this situation by only taking the
port lock in cdns_uart_console_write if port->sysrq unset. However, if
(as shown above) cdns_uart_console_write runs before port->sysrq is set,
then it will try to take the port lock anyway. This may result in a
deadlock.
Fix this by splitting sysrq handling into two parts. We use the prepare
helper under the port lock and defer handling until we release the lock.
Fixes: 74ea66d4ca06 ("tty: xuartps: Improve sysrq handling")
Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
Cc: stable@vger.kernel.org # c980248179d: serial: xilinx_uartps: Use port lock wrappers
Acked-by: John Ogness <john.ogness@linutronix.de>
Link: https://lore.kernel.org/r/20250110213822.2107462-1-sean.anderson@linux.dev
Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/serial')
| -rw-r--r-- | drivers/tty/serial/xilinx_uartps.c | 10 |
1 files changed, 4 insertions, 6 deletions
diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c index 2e5e86a00a77..7f83d2780017 100644 --- a/drivers/tty/serial/xilinx_uartps.c +++ b/drivers/tty/serial/xilinx_uartps.c @@ -268,7 +268,7 @@ static void cdns_uart_handle_rx(void *dev_id, unsigned int isrstatus) continue; } - if (uart_handle_sysrq_char(port, data)) + if (uart_prepare_sysrq_char(port, data)) continue; if (is_rxbs_support) { @@ -369,7 +369,7 @@ static irqreturn_t cdns_uart_isr(int irq, void *dev_id) !(readl(port->membase + CDNS_UART_CR) & CDNS_UART_CR_RX_DIS)) cdns_uart_handle_rx(dev_id, isrstatus); - spin_unlock(&port->lock); + uart_unlock_and_check_sysrq(port); return IRQ_HANDLED; } @@ -1229,10 +1229,8 @@ static void cdns_uart_console_write(struct console *co, const char *s, unsigned int imr, ctrl; int locked = 1; - if (port->sysrq) - locked = 0; - else if (oops_in_progress) - locked = spin_trylock_irqsave(&port->lock, flags); + if (oops_in_progress) + locked = uart_port_trylock_irqsave(port, &flags); else spin_lock_irqsave(&port->lock, flags); |