Hyper-V serial port is very slow on multi-vCPU guest, this causes soflockups on intensive console writes. Touch nmi watchdog after putting every char on port to avoid the issue for all serial drivers, the overhead should be small. This is just a part of the fix: serial8250_console_write() disables irqs for all its execution time (which on such slow consoles can be dozens of seconds), it should be possible to observe devices being stuck on this CPU. We need to find a better way, e.g. do output in batches enabling irqs in between. Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> --- drivers/tty/serial/serial_core.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index f368520..cc05785 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -33,7 +33,7 @@ #include <linux/serial.h> /* for serial_state and serial_icounter_struct */ #include <linux/serial_core.h> #include <linux/delay.h> -#include <linux/mutex.h> +#include <linux/nmi.h> #include <asm/irq.h> #include <asm/uaccess.h> @@ -1792,6 +1792,7 @@ void uart_console_write(struct uart_port *port, const char *s, if (*s == '\n') putchar(port, '\r'); putchar(port, *s); + touch_nmi_watchdog(); } } EXPORT_SYMBOL_GPL(uart_console_write); -- 2.4.3 -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
