From: Eugene Shatokhin <eugene.shatokhin@xxxxxxxxxx> Date: Wed, 19 Aug 2015 14:59:01 +0300 > So the following might be possible, although unlikely: > > CPU0 CPU1 > clear_bit: read dev->flags > clear_bit: clear EVENT_RX_KILL in the read value > > dev->flags=0; > > clear_bit: write updated dev->flags > > As a result, dev->flags may become non-zero again. Is this really possible? Stores really are "atomic" in the sense that the do their update in one indivisible operation. Atomic operations like clear_bit also will behave that way. If a clear_bit is in progress, the "dev->flags=0" store will not be able to grab the cache line exclusively until the clear_bit is done. So I think the above sequent of events is completely impossible. Once a clear_bit starts, a write by another foreign agent on the bus is absolutely impossible to legally occur until the clear_bit completes. I think this is a non-issue. -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
