On Sun, May 19, 2013 at 04:23:22PM -0400, Steven Rostedt wrote: > On Sun, 2013-05-19 at 19:40 +0300, Michael S. Tsirkin wrote: > > > OK I get it. So let me correct myself. The simple code > > that does something like this under a spinlock: > > > preempt_disable > > > pagefault_disable > > > error = copy_to_user > > > pagefault_enable > > > preempt_enable > > > > > is not doing anything wrong and should not get a warning, > > as long as error is handled correctly later. > > Right? > > I came in mid thread and I don't know the context. The context is that I want to change might_fault from might_sleep to might_sleep_if(!in_atomic()) so that above does not trigger warnings even with CONFIG_DEBUG_ATOMIC_SLEEP enabled. > Anyway, the above > looks to me as you just don't want to sleep. Exactly. upstream we can just do pagefault_disable but to make this code -rt ready it's best to do preempt_disable as well. > If you try to copy data to > user space that happens not to be currently mapped for any reason, you > will get an error. Even if the address space is completely valid. Is > that what you want? > > -- Steve > Yes, this is by design. We detect that and bounce the work to a thread outside any locks. Thanks, -- MST -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>