tree: https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git locking/futex head: 3e6fb0c7cd6f4839a2ac03396781247f7e902875 commit: 038e21d9eaa0a4bc011f9d4e8d006e8072a48422 [4/8] futex: Implement sys_futex_waitv() config: um-i386_defconfig (attached as .config) compiler: gcc-9 (Debian 9.3.0-22) 9.3.0 reproduce (this is a W=1 build): # https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git/commit/?... git remote add peterz-queue https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git git fetch --no-tags peterz-queue locking/futex git checkout 038e21d9eaa0a4bc011f9d4e8d006e8072a48422 # save the attached .config to linux build tree make W=1 ARCH=um SUBARCH=i386 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>): kernel/futex/core.c: In function 'futex_wait_multiple_setup': 2804 | u32 __user *uaddr = (u32 __user *)vs[i].w.uaddr; | ^ vim +2804 kernel/futex/core.c 2750 2751 /** 2752 * futex_wait_multiple_setup - Prepare to wait and enqueue multiple futexes 2753 * @vs: The futex list to wait on 2754 * @count: The size of the list 2755 * @awaken: Index of the last awoken futex, if any. Used to notify the 2756 * caller that it can return this index to userspace (return parameter) 2757 * 2758 * Prepare multiple futexes in a single step and enqueue them. This may fail if 2759 * the futex list is invalid or if any futex was already awoken. On success the 2760 * task is ready to interruptible sleep. 2761 * 2762 * Return: 2763 * - 1 - One of the futexes was awaken by another thread 2764 * - 0 - Success 2765 * - <0 - -EFAULT, -EWOULDBLOCK or -EINVAL 2766 */ 2767 static int futex_wait_multiple_setup(struct futex_vector *vs, int count, int *awaken) 2768 { 2769 struct futex_hash_bucket *hb; 2770 bool retry = false; 2771 int ret, i; 2772 u32 uval; 2773 2774 /* 2775 * Enqueuing multiple futexes is tricky, because we need to enqueue 2776 * each futex in the list before dealing with the next one to avoid 2777 * deadlocking on the hash bucket. But, before enqueuing, we need to 2778 * make sure that current->state is TASK_INTERRUPTIBLE, so we don't 2779 * absorb any awake events, which cannot be done before the 2780 * get_futex_key of the next key, because it calls get_user_pages, 2781 * which can sleep. Thus, we fetch the list of futexes keys in two 2782 * steps, by first pinning all the memory keys in the futex key, and 2783 * only then we read each key and queue the corresponding futex. 2784 * 2785 * Private futexes doesn't need to recalculate hash in retry, so skip 2786 * get_futex_key() when retrying. 2787 */ 2788 retry: 2789 for (i = 0; i < count; i++) { 2790 if ((vs[i].w.flags & FUTEX_PRIVATE_FLAG) && retry) 2791 continue; 2792 2793 ret = get_futex_key(u64_to_user_ptr(vs[i].w.uaddr), 2794 !(vs[i].w.flags & FUTEX_PRIVATE_FLAG), 2795 &vs[i].q.key, FUTEX_READ); 2796 2797 if (unlikely(ret)) 2798 return ret; 2799 } 2800 2801 set_current_state(TASK_INTERRUPTIBLE); 2802 2803 for (i = 0; i < count; i++) { 2805 struct futex_q *q = &vs[i].q; 2806 u32 val = (u32)vs[i].w.val; 2807 2808 hb = queue_lock(q); 2809 ret = get_futex_value_locked(&uval, uaddr); 2810 2811 if (!ret && uval == val) { 2812 /* 2813 * The bucket lock can't be held while dealing with the 2814 * next futex. Queue each futex at this moment so hb can 2815 * be unlocked. 2816 */ 2817 queue_me(q, hb); 2818 continue; 2819 } 2820 2821 queue_unlock(hb); 2822 __set_current_state(TASK_RUNNING); 2823 2824 /* 2825 * Even if something went wrong, if we find out that a futex 2826 * was awaken, we don't return error and return this index to 2827 * userspace 2828 */ 2829 *awaken = unqueue_multiple(vs, i); 2830 if (*awaken >= 0) 2831 return 1; 2832 2833 if (uval != val) 2834 return -EWOULDBLOCK; 2835 2836 if (ret) { 2837 /* 2838 * If we need to handle a page fault, we need to do so 2839 * without any lock and any enqueued futex (otherwise 2840 * we could lose some wakeup). So we do it here, after 2841 * undoing all the work done so far. In success, we 2842 * retry all the work. 2843 */ 2844 if (get_user(uval, uaddr)) 2845 return -EFAULT; 2846 2847 retry = true; 2848 goto retry; 2849 } 2850 } 2851 2852 return 0; 2853 } 2854 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org