Am 07.05.2015 um 11:48 schrieb Ingo Molnar: > > * Andrew Morton <[email protected]> wrote: > >> On Wed, 6 May 2015 19:50:24 +0200 David Hildenbrand >> <[email protected]> wrote: >> >>> As Peter asked me to also do the decoupling in one shot, this is >>> the new series. >>> >>> I recently discovered that might_fault() doesn't call might_sleep() >>> anymore. Therefore bugs like: >>> >>> spin_lock(&lock); >>> rc = copy_to_user(...); >>> spin_unlock(&lock); >>> >>> would not be detected with CONFIG_DEBUG_ATOMIC_SLEEP. The code was >>> changed to disable false positives for code like: >>> >>> pagefault_disable(); >>> rc = copy_to_user(...); >>> pagefault_enable(); >>> >>> Whereby the caller wants do deal with failures. >> >> hm, that was a significant screwup. I wonder how many bugs we >> subsequently added. > > So I'm wondering what the motivation was to allow things like: > > pagefault_disable(); > rc = copy_to_user(...); > pagefault_enable(); > > and to declare it a false positive? > > AFAICS most uses are indeed atomic: > > pagefault_disable(); > ret = futex_atomic_cmpxchg_inatomic(curval, uaddr, uval, newval); > pagefault_enable(); > > so why not make it explicitly atomic again?
Hmm, I am probably misreading that, but it sound as you suggest to go back to Davids first proposal https://lkml.org/lkml/2014/11/25/436 which makes might_fault to also contain might_sleep. Correct? Christian -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
