On (06/19/18 10:30), Petr Mladek wrote: > It is re-entrant via printk(). I mean that any printk() called inside > the locked sections might cause recursion if the same lock is needed > also by con->write() callbacks. Perhaps Alan meant that we cannot return back to tty once we passed the control from tty to printk -> uart serial console. So tty is probably (but I didn't check) not re-entrant, but uart definitely is re-entrant: IRQ -> uart console -> tty -> printk -> uart console. The patch set attempts to address several issues, and re-entrant uart is just one of them. [..] > This patchset forces safe context around TTY and UART locks. Right. > In fact, the deferred context would be enough to prevent > all the mentioned deadlocks. Agree. But we can leave it as a printk_safe implementation detail and change it later, outside of this patch, to avoid further confusion. > IMHO, the only question is if people might get familiar with > yet another spin_lock API. Right. That's why I thought about renaming uart_port and tty_port ->lock to ->____lock. So the naming will suggest [hopefully] that those locks are not meant to be used directly [anymore] and instead people should use uart_port_lock/tty_port_lock API. -ss -- 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
