On Tue, Jul 07, 2015 at 08:13:59AM +0000, Taichi Kageyama wrote: > On 2015/06/05 18:55, Taichi Kageyama wrote: > > This patch set provides a workaround to avoid the following problem. > > It's based on Linux 4.1-rc3 mainstream kernel. > > I've tested this patch set on x86-64 machine and KVM. > > > > Problem > > -------------------------- > > There're cases where autoconfig_irq() fails during boot. > > In these cases, the console doesn't work in interrupt mode, > > the mode cannot be changed anymore, and "input overrun" > > (which can make operation mistakes) happens easily. > > This problem happens with high rate every boot once it occurs > > because the boot sequence is always almost same. > > I saw the original problem on RHEL6.6. > > > > Fix > > -------------------------- > > serial: 8250: Fix autoconfig_irq() to avoid race conditions > > Fix one of autoconfig_irq() failure case. > > serial: 8250: Allow to skip autoconfig_irq() for a console > > Provide a workaround to avoid other autoconfig_irq() failure cases. > > > > Conditions of Reproduction > > -------------------------- > > - Build with CONFIG_SERIAL_8250_DETECT_IRQ. > > - Need non-PnP console serial or PnP console with no CONFIG_SERIAL_8250_PNP > > - Kick printk() repeatedly on the CPU which can handle an interrupt > > from a console serial during autoconfig_irq(). The CPU is basically cpu0. > > - Disable the interrupt of the CPU for longer during autoconfig_irq(). > > > > Note > > -------------------------- > > Ideally, I think autoconfig_irq() should be fixed completely, > > but it's hard from the following points > > as long as auto_irq algorithm is used. > > - How long it should wait for an interrrupt > > - How to assure the interrupt of the CPU enabled during auto_irq > > - How to know which CPU can handle an interrupt from a serial. > > > > Do you have any other idea? > > In my opinion, providing a workaround is better than > > applying big changes to the old function for legacy devices. > > > > Taichi Kageyama (2): > > serial: 8250: Fix autoconfig_irq() to avoid race conditions > > serial: 8250: Allow to skip autoconfig_irq() for a console > > > > drivers/tty/serial/8250/8250_core.c | 23 +++++++++++++++++++++++ > > 1 files changed, 23 insertions(+), 0 deletions(-) > > > > Could you review this patch set? Relax, it's in my queue... -- 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
