On 2015/07/24 7:32, gregkh@xxxxxxxxxxxxxxxxxxx wrote: > On Fri, Jun 05, 2015 at 09:57:40AM +0000, Taichi Kageyama wrote: >> The following race conditions can happen if a serial is used as console. >> Case1. CPU_B handles an interrupt from a serial >> autoconfig_irq() fails whether the interrupt is raised or not >> if CPU_B is disabled to handle interrupts for longer than it expects. >> Case2. CPU_B clears UART_IER just after CPU_A sets UART_IER >> A serial may not make an interrupt. >> autoconfig_irq() can fail if the interrupt is not raised. >> Case3. CPU_A sets UART_IER just after CPU_B clears UART_IER >> This is an unexpected behavior for uart_console_write(). >> >> CPU_A [autoconfig_irq] CPU_B [serial8250_console_write] >> ----------------------------------------------------------------- >> probe_irq_on() spin_lock_irqsave(&port->lock,) >> serial_outp(,UART_IER,0x0f) serial_out(,UART_IER,0) >> udelay(20); uart_console_write() >> probe_irq_off() >> spin_unlock_irqrestore(&port->lock,) >> ----------------------------------------------------------------- >> >> If autoconfig_irq() fails, 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. >> >> Signed-off-by: Taichi Kageyama <t-kageyama@xxxxxxxxxxxxx> >> Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> >> Reviewed-by: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx> >> --- >> drivers/tty/serial/8250/8250_core.c | 6 ++++++ >> 1 files changed, 6 insertions(+), 0 deletions(-) > > Does not apply to 4.2-rc3 :( > Sorry for the trouble and late reply. It's my fault. It was encoded as base64 by Exchange. I sent new patch set including this patch. I updated commit log. Regards, Taichi-- 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
