serial: pxa: hold port.lock when reporting modem line changes

lumag · gregkh · commit 50d1e7d1077b · 2014-11-26T19:35:49.000-08:00
Both uart_handle_dcd_change() and uart_handle_cts_change() require a port lock to be held and will emit a warning when lockdep is enabled. Held corresponding lock. This fixes the following warnings: ------------[ cut here ]------------ WARNING: CPU: 0 PID: 0 at drivers/tty/serial/serial_core.c:2760 uart_handle_dcd_change+0xc8/0xf8() Modules linked in: CPU: 0 PID: 0 Comm: swapper Not tainted 3.18.0-rc5+ torvalds#26 [<c000dff8>] (unwind_backtrace) from [<c000bc70>] (show_stack+0x10/0x14) [<c000bc70>] (show_stack) from [<c00192ac>] (warn_slowpath_common+0x6c/0x8c) [<c00192ac>] (warn_slowpath_common) from [<c00192e8>] (warn_slowpath_null+0x1c/0x24) [<c00192e8>] (warn_slowpath_null) from [<c0182984>] (uart_handle_dcd_change+0xc8/0xf8) [<c0182984>] (uart_handle_dcd_change) from [<c018625c>] (serial_pxa_irq+0x268/0x3b0) [<c018625c>] (serial_pxa_irq) from [<c004d0d4>] (handle_irq_event_percpu+0x50/0x16c) [<c004d0d4>] (handle_irq_event_percpu) from [<c004d22c>] (handle_irq_event+0x3c/0x5c) [<c004d22c>] (handle_irq_event) from [<c004f7d0>] (handle_level_irq+0x94/0x118) [<c004f7d0>] (handle_level_irq) from [<c004ca0c>] (generic_handle_irq+0x20/0x30) [<c004ca0c>] (generic_handle_irq) from [<c004cbe0>] (__handle_domain_irq+0x38/0x70) [<c004cbe0>] (__handle_domain_irq) from [<c00085c4>] (ichp_handle_irq+0x24/0x34) [<c00085c4>] (ichp_handle_irq) from [<c000c7e4>] (__irq_svc+0x44/0x54) Exception stack(0xc07c7f58 to 0xc07c7fa0) 7f40: 00000001 00000001 7f60: 00000000 20000013 c07c6000 00000000 00000000 c07ce0a4 c07d7798 00000000 7f80: c07e8fb8 0000004c 00000000 c07c7fa0 c0044798 c0009f20 20000013 ffffffff [<c000c7e4>] (__irq_svc) from [<c0009f20>] (arch_cpu_idle+0x28/0x38) [<c0009f20>] (arch_cpu_idle) from [<c003c974>] (cpu_startup_entry+0x1b8/0x220) [<c003c974>] (cpu_startup_entry) from [<c0338c54>] (start_kernel+0x39c/0x40c) ---[ end trace 4c1b7ae03f6d9d30 ]--- ------------[ cut here ]------------ WARNING: CPU: 0 PID: 0 at drivers/tty/serial/serial_core.c:2791 uart_handle_cts_change+0xa0/0xdc() Modules linked in: CPU: 0 PID: 0 Comm: swapper Tainted: G W 3.18.0-rc5+ torvalds#26 [<c000dff8>] (unwind_backtrace) from [<c000bc70>] (show_stack+0x10/0x14) [<c000bc70>] (show_stack) from [<c00192ac>] (warn_slowpath_common+0x6c/0x8c) [<c00192ac>] (warn_slowpath_common) from [<c00192e8>] (warn_slowpath_null+0x1c/0x24) [<c00192e8>] (warn_slowpath_null) from [<c018528c>] (uart_handle_cts_change+0xa0/0xdc) [<c018528c>] (uart_handle_cts_change) from [<c018624c>] (serial_pxa_irq+0x258/0x3b0) [<c018624c>] (serial_pxa_irq) from [<c004d0d4>] (handle_irq_event_percpu+0x50/0x16c) [<c004d0d4>] (handle_irq_event_percpu) from [<c004d22c>] (handle_irq_event+0x3c/0x5c) [<c004d22c>] (handle_irq_event) from [<c004f7d0>] (handle_level_irq+0x94/0x118) [<c004f7d0>] (handle_level_irq) from [<c004ca0c>] (generic_handle_irq+0x20/0x30) [<c004ca0c>] (generic_handle_irq) from [<c004cbe0>] (__handle_domain_irq+0x38/0x70) [<c004cbe0>] (__handle_domain_irq) from [<c00085c4>] (ichp_handle_irq+0x24/0x34) [<c00085c4>] (ichp_handle_irq) from [<c000c7e4>] (__irq_svc+0x44/0x54) Exception stack(0xc07c7f58 to 0xc07c7fa0) 7f40: 00000001 00000001 7f60: 00000000 20000013 c07c6000 00000000 00000000 c07ce0a4 c07d7798 00000000 7f80: c07e8fb8 0000004c 00000000 c07c7fa0 c0044798 c0009f20 20000013 ffffffff [<c000c7e4>] (__irq_svc) from [<c0009f20>] (arch_cpu_idle+0x28/0x38) [<c0009f20>] (arch_cpu_idle) from [<c003c974>] (cpu_startup_entry+0x1b8/0x220) [<c003c974>] (cpu_startup_entry) from [<c0338c54>] (start_kernel+0x39c/0x40c) ---[ end trace 4c1b7ae03f6d9d31 ]--- Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com> Acked-by: Robert Jarzmik <robert.jarzmik@free.fr> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/serial/pxa.c b/drivers/tty/serial/pxa.c
@@ -223,6 +223,7 @@ static void serial_pxa_start_tx(struct uart_port *port)
 	}
 }
 
+/* should hold up->port.lock */
 static inline void check_modem_status(struct uart_pxa_port *up)
 {
 	int status;
@@ -255,12 +256,14 @@ static inline irqreturn_t serial_pxa_irq(int irq, void *dev_id)
 	iir = serial_in(up, UART_IIR);
 	if (iir & UART_IIR_NO_INT)
 		return IRQ_NONE;
+	spin_lock(&up->port.lock);
 	lsr = serial_in(up, UART_LSR);
 	if (lsr & UART_LSR_DR)
 		receive_chars(up, &lsr);
 	check_modem_status(up);
 	if (lsr & UART_LSR_THRE)
 		transmit_chars(up);
+	spin_unlock(&up->port.lock);
 	return IRQ_HANDLED;
 }
 

Original file line number	Diff line number	Diff line change
`@@ -223,6 +223,7 @@ static void serial_pxa_start_tx(struct uart_port *port)`
`223`	`223`	`}`
`224`	`224`	`}`
`225`	`225`
	`226`	`+/* should hold up->port.lock */`
`226`	`227`	`static inline void check_modem_status(struct uart_pxa_port *up)`
`227`	`228`	`{`
`228`	`229`	`int status;`
`@@ -255,12 +256,14 @@ static inline irqreturn_t serial_pxa_irq(int irq, void *dev_id)`
`255`	`256`	`iir = serial_in(up, UART_IIR);`
`256`	`257`	`if (iir & UART_IIR_NO_INT)`
`257`	`258`	`return IRQ_NONE;`
	`259`	`+ spin_lock(&up->port.lock);`
`258`	`260`	`lsr = serial_in(up, UART_LSR);`
`259`	`261`	`if (lsr & UART_LSR_DR)`
`260`	`262`	`receive_chars(up, &lsr);`
`261`	`263`	`check_modem_status(up);`
`262`	`264`	`if (lsr & UART_LSR_THRE)`
`263`	`265`	`transmit_chars(up);`
	`266`	`+ spin_unlock(&up->port.lock);`
`264`	`267`	`return IRQ_HANDLED;`
`265`	`268`	`}`
`266`	`269`