On Fri, Jan 16, 2015 at 08:28:06PM +0100, Michael Kerrisk (man-pages) wrote: > From: Michael Kerrisk <mtk.manpa...@gmail.com> > > This patch fixes two separate buglets in calls to futex_lock_pi(): > > * Eliminate unused 'detect' argument > * Change unused 'timeout' argument of FUTEX_TRYLOCK_PI to NULL
One might argue these should be two separate fixes. Since both are trivial and functional no-ops, I'm going to ignore it and consider it a "cleanup" :-) Thomas may disagree. > > The 'detect' argument of futex_lock_pi() seems never to have been > used (when it was included with the initial PI mutex implementation > in Linux 2.6.18, all checks against its value were disabled by > ANDing against 0 (i.e., if (detect... && 0)), and with > commit 778e9a9c3e7193ea9f434f382947155ffb59c755, any mention of > this argument in futex_lock_pi() went way altogether. Its presence > now serves only to confuse readers of the code, by giving the > impression that the futex() FUTEX_LOCK_PI operation actually does > use the 'val' argument. This patch removes the argument. > > The futex_lock_pi() call that corresponds to FUTEX_TRYLOCK_PI includes > 'timeout' as one of its arguments. This misleads the reader into thinking > that the FUTEX_TRYLOCK_PI operation does employ timeouts for some sensible > purpose; but it does not. Indeed, it cannot, because the checks at the > start of sys_futex() exclude FUTEX_TRYLOCK_PI from the set of operations > that do copy_from_user() on the timeout argument. So, in the > FUTEX_TRYLOCK_PI futex_lock_pi() call it would be simplest to change > 'timeout' to 'NULL'. This patch does that. > > Signed-off-by: Michael Kerrisk <mtk.manpa...@gmail.com> Good and correct changes each. Reviewed-by: Darren Hart <dvh...@linux.intel.com> Thanks Michael, -- Darren Hart Intel Open Source Technology Center -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
