On Thu, 20 Mar 2008, Andrew Morton wrote: > On Thu, 20 Mar 2008 21:36:04 -0300 Henrique de Moraes Holschuh <hmh@xxxxxxxxxx> wrote: > > > Well, so far so good for LEDs, but what about the other users of in_atomic > > that apparently should not be doing it either? > > Ho hum. Lots of cc's added. ... > The usual pattern for most of the above is > > if (!in_atomic()) > do_something_which_might_sleep(); > > problem is, in_atomic() returns false inside spinlock on non-preptible > kernels. So if anyone calls those functions inside spinlock they will > incorrectly schedule and another task can then come in and try take the > already-held lock. > > Now, it happens that in_atomic() returns true on non-preemtible kernels > when running in interrupt or softirq context. But if the above code really > is using in_atomic() to detect am-i-called-from-interrupt and NOT > am-i-called-from-inside-spinlock, they should be using in_irq(), > in_softirq() or in_interrupt(). Presumably most of these places are actually trying to detect am-i-allowed-to-sleep. Isn't that what in_atomic() is supposed to do? Why doesn't it do that in non-preemptible kernels? For that matter, isn't it also the sort of thing that might_sleep() is supposed to check? But looking at the definitions in include/linux/kernel.h, it appears that might_sleep() does nothing at all when neither CONFIG_PREEMPT_VOLUNTARY nor CONFIG_DEBUG_SPINLOCK_SLEEP is set. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
