Merge branch 'akpm' (patches from Andrew)

Merge misc fixes from Andrew Morton:
 "14 fixes and one selftest to verify the ipc fixes herein"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
  mm: limit boost_watermark on small zones
  ubsan: disable UBSAN_ALIGNMENT under COMPILE_TEST
  mm/vmscan: remove unnecessary argument description of isolate_lru_pages()
  epoll: atomically remove wait entry on wake up
  kselftests: introduce new epoll60 testcase for catching lost wakeups
  percpu: make pcpu_alloc() aware of current gfp context
  mm/slub: fix incorrect interpretation of s->offset
  scripts/gdb: repair rb_first() and rb_last()
  eventpoll: fix missing wakeup for ovflist in ep_poll_callback
  arch/x86/kvm/svm/sev.c: change flag passed to GUP fast in sev_pin_memory()
  scripts/decodecode: fix trapping instruction formatting
  kernel/kcov.c: fix typos in kcov_remote_start documentation
  mm/page_alloc: fix watchdog soft lockups during set_zone_contiguous()
  mm, memcg: fix error return value of mem_cgroup_css_alloc()
  ipc/mqueue.c: change __do_notify() to bypass check_kill_permission()

arch/x86/kvm/svm/sev.c

@@ -345,7 +345,7 @@ static struct page **sev_pin_memory(struct kvm *kvm, unsigned long uaddr,
 		return NULL;
 
 	/* Pin the user virtual address. */
-	npinned = get_user_pages_fast(uaddr, npages, FOLL_WRITE, pages);
+	npinned = get_user_pages_fast(uaddr, npages, write ? FOLL_WRITE : 0, pages);
 	if (npinned != npages) {
 		pr_err("SEV: Failure locking %lu pages.\n", npages);
 		goto err;

fs/eventpoll.c

@@ -1171,6 +1171,10 @@ static inline bool chain_epi_lockless(struct epitem *epi)
 {
 	struct eventpoll *ep = epi->ep;
 
+	/* Fast preliminary check */
+	if (epi->next != EP_UNACTIVE_PTR)
+		return false;
+
 	/* Check that the same epi has not been just chained from another CPU */
 	if (cmpxchg(&epi->next, EP_UNACTIVE_PTR, NULL) != EP_UNACTIVE_PTR)
 		return false;
@@ -1237,15 +1241,11 @@ static int ep_poll_callback(wait_queue_entry_t *wait, unsigned mode, int sync, v
 	 * chained in ep->ovflist and requeued later on.
 	 */
 	if (READ_ONCE(ep->ovflist) != EP_UNACTIVE_PTR) {
-		if (epi->next == EP_UNACTIVE_PTR &&
-		    chain_epi_lockless(epi))
+		if (chain_epi_lockless(epi))
 			ep_pm_stay_awake_rcu(epi);
-		goto out_unlock;
-	}
-
-	/* If this file is already in the ready list we exit soon */
-	if (!ep_is_linked(epi) &&
-	    list_add_tail_lockless(&epi->rdllink, &ep->rdllist)) {
+	} else if (!ep_is_linked(epi)) {
+		/* In the usual case, add event to ready list. */
+		if (list_add_tail_lockless(&epi->rdllink, &ep->rdllist))
 			ep_pm_stay_awake_rcu(epi);
 	}
 
@@ -1822,7 +1822,6 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
 {
 	int res = 0, eavail, timed_out = 0;
 	u64 slack = 0;
-	bool waiter = false;
 	wait_queue_entry_t wait;
 	ktime_t expires, *to = NULL;
 
@@ -1867,21 +1866,23 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
 	 */
 	ep_reset_busy_poll_napi_id(ep);
 
+	do {
 		/*
-	 * We don't have any available event to return to the caller.  We need
-	 * to sleep here, and we will be woken by ep_poll_callback() when events
-	 * become available.
+		 * Internally init_wait() uses autoremove_wake_function(),
+		 * thus wait entry is removed from the wait queue on each
+		 * wakeup. Why it is important? In case of several waiters
+		 * each new wakeup will hit the next waiter, giving it the
+		 * chance to harvest new event. Otherwise wakeup can be
+		 * lost. This is also good performance-wise, because on
+		 * normal wakeup path no need to call __remove_wait_queue()
+		 * explicitly, thus ep->lock is not taken, which halts the
+		 * event delivery.
 		 */
-	if (!waiter) {
-		waiter = true;
-		init_waitqueue_entry(&wait, current);
-
+		init_wait(&wait);
 		write_lock_irq(&ep->lock);
 		__add_wait_queue_exclusive(&ep->wq, &wait);
 		write_unlock_irq(&ep->lock);
-	}
 
-	for (;;) {
 		/*
 		 * We don't want to sleep if the ep_poll_callback() sends us
 		 * a wakeup in between. That's why we set the task state
@@ -1911,10 +1912,20 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
 			timed_out = 1;
 			break;
 		}
-	}
+
+		/* We were woken up, thus go and try to harvest some events */
+		eavail = 1;
+
+	} while (0);
 
 	__set_current_state(TASK_RUNNING);
 
+	if (!list_empty_careful(&wait.entry)) {
+		write_lock_irq(&ep->lock);
+		__remove_wait_queue(&ep->wq, &wait);
+		write_unlock_irq(&ep->lock);
+	}
+
 send_events:
 	/*
 	 * Try to transfer events to user space. In case we get 0 events and
@@ -1925,12 +1936,6 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
 	    !(res = ep_send_events(ep, events, maxevents)) && !timed_out)
 		goto fetch_events;
 
-	if (waiter) {
-		write_lock_irq(&ep->lock);
-		__remove_wait_queue(&ep->wq, &wait);
-		write_unlock_irq(&ep->lock);
-	}
-
 	return res;
 }
 

ipc/mqueue.c

@@ -142,6 +142,7 @@ struct mqueue_inode_info {
 
 	struct sigevent notify;
 	struct pid *notify_owner;
+	u32 notify_self_exec_id;
 	struct user_namespace *notify_user_ns;
 	struct user_struct *user;	/* user who created, for accounting */
 	struct sock *notify_sock;
@@ -773,28 +774,44 @@ static void __do_notify(struct mqueue_inode_info *info)
 	 * synchronously. */
 	if (info->notify_owner &&
 	    info->attr.mq_curmsgs == 1) {
-		struct kernel_siginfo sig_i;
 		switch (info->notify.sigev_notify) {
 		case SIGEV_NONE:
 			break;
-		case SIGEV_SIGNAL:
-			/* sends signal */
+		case SIGEV_SIGNAL: {
+			struct kernel_siginfo sig_i;
+			struct task_struct *task;
+
+			/* do_mq_notify() accepts sigev_signo == 0, why?? */
+			if (!info->notify.sigev_signo)
+				break;
 
 			clear_siginfo(&sig_i);
 			sig_i.si_signo = info->notify.sigev_signo;
 			sig_i.si_errno = 0;
 			sig_i.si_code = SI_MESGQ;
 			sig_i.si_value = info->notify.sigev_value;
-			/* map current pid/uid into info->owner's namespaces */
 			rcu_read_lock();
+			/* map current pid/uid into info->owner's namespaces */
 			sig_i.si_pid = task_tgid_nr_ns(current,
 						ns_of_pid(info->notify_owner));
-			sig_i.si_uid = from_kuid_munged(info->notify_user_ns, current_uid());
+			sig_i.si_uid = from_kuid_munged(info->notify_user_ns,
+						current_uid());
+			/*
+			 * We can't use kill_pid_info(), this signal should
+			 * bypass check_kill_permission(). It is from kernel
+			 * but si_fromuser() can't know this.
+			 * We do check the self_exec_id, to avoid sending
+			 * signals to programs that don't expect them.
+			 */
+			task = pid_task(info->notify_owner, PIDTYPE_TGID);
+			if (task && task->self_exec_id ==
+						info->notify_self_exec_id) {
+				do_send_sig_info(info->notify.sigev_signo,
+						&sig_i, task, PIDTYPE_TGID);
+			}
 			rcu_read_unlock();
-
-			kill_pid_info(info->notify.sigev_signo,
-				      &sig_i, info->notify_owner);
 			break;
+		}
 		case SIGEV_THREAD:
 			set_cookie(info->notify_cookie, NOTIFY_WOKENUP);
 			netlink_sendskb(info->notify_sock, info->notify_cookie);
@@ -1383,6 +1400,7 @@ static int do_mq_notify(mqd_t mqdes, const struct sigevent *notification)
 			info->notify.sigev_signo = notification->sigev_signo;
 			info->notify.sigev_value = notification->sigev_value;
 			info->notify.sigev_notify = SIGEV_SIGNAL;
+			info->notify_self_exec_id = current->self_exec_id;
 			break;
 		}
 

kernel/kcov.c

@@ -740,8 +740,8 @@ static const struct file_operations kcov_fops = {
  * kcov_remote_handle() with KCOV_SUBSYSTEM_COMMON as the subsystem id and an
  * arbitrary 4-byte non-zero number as the instance id). This common handle
  * then gets saved into the task_struct of the process that issued the
- * KCOV_REMOTE_ENABLE ioctl. When this proccess issues system calls that spawn
- * kernel threads, the common handle must be retrived via kcov_common_handle()
+ * KCOV_REMOTE_ENABLE ioctl. When this process issues system calls that spawn
+ * kernel threads, the common handle must be retrieved via kcov_common_handle()
  * and passed to the spawned threads via custom annotations. Those kernel
  * threads must in turn be annotated with kcov_remote_start(common_handle) and
  * kcov_remote_stop(). All of the threads that are spawned by the same process

lib/Kconfig.ubsan

@@ -60,18 +60,15 @@ config UBSAN_SANITIZE_ALL
 	  Enabling this option will get kernel image size increased
 	  significantly.
 
-config UBSAN_NO_ALIGNMENT
-	bool "Disable checking of pointers alignment"
-	default y if HAVE_EFFICIENT_UNALIGNED_ACCESS
+config UBSAN_ALIGNMENT
+	bool "Enable checks for pointers alignment"
+	default !HAVE_EFFICIENT_UNALIGNED_ACCESS
+	depends on !X86 || !COMPILE_TEST
 	help
-	  This option disables the check of unaligned memory accesses.
-	  This option should be used when building allmodconfig.
-	  Disabling this option on architectures that support unaligned
+	  This option enables the check of unaligned memory accesses.
+	  Enabling this option on architectures that support unaligned
 	  accesses may produce a lot of false positives.
 
-config UBSAN_ALIGNMENT
-	def_bool !UBSAN_NO_ALIGNMENT
-
 config TEST_UBSAN
 	tristate "Module for testing for undefined behavior detection"
 	depends on m

mm/memcontrol.c

@@ -4990,19 +4990,22 @@ static struct mem_cgroup *mem_cgroup_alloc(void)
 	unsigned int size;
 	int node;
 	int __maybe_unused i;
+	long error = -ENOMEM;
 
 	size = sizeof(struct mem_cgroup);
 	size += nr_node_ids * sizeof(struct mem_cgroup_per_node *);
 
 	memcg = kzalloc(size, GFP_KERNEL);
 	if (!memcg)
-		return NULL;
+		return ERR_PTR(error);
 
 	memcg->id.id = idr_alloc(&mem_cgroup_idr, NULL,
 				 1, MEM_CGROUP_ID_MAX,
 				 GFP_KERNEL);
-	if (memcg->id.id < 0)
+	if (memcg->id.id < 0) {
+		error = memcg->id.id;
 		goto fail;
+	}
 
 	memcg->vmstats_local = alloc_percpu(struct memcg_vmstats_percpu);
 	if (!memcg->vmstats_local)
@@ -5046,7 +5049,7 @@ static struct mem_cgroup *mem_cgroup_alloc(void)
 fail:
 	mem_cgroup_id_remove(memcg);
 	__mem_cgroup_free(memcg);
-	return NULL;
+	return ERR_PTR(error);
 }
 
 static struct cgroup_subsys_state * __ref
@@ -5057,8 +5060,8 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
 	long error = -ENOMEM;
 
 	memcg = mem_cgroup_alloc();
-	if (!memcg)
-		return ERR_PTR(error);
+	if (IS_ERR(memcg))
+		return ERR_CAST(memcg);
 
 	WRITE_ONCE(memcg->high, PAGE_COUNTER_MAX);
 	memcg->soft_limit = PAGE_COUNTER_MAX;
@@ -5108,7 +5111,7 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
 fail:
 	mem_cgroup_id_remove(memcg);
 	mem_cgroup_free(memcg);
-	return ERR_PTR(-ENOMEM);
+	return ERR_PTR(error);
 }
 
 static int mem_cgroup_css_online(struct cgroup_subsys_state *css)

mm/page_alloc.c

@@ -1607,6 +1607,7 @@ void set_zone_contiguous(struct zone *zone)
 		if (!__pageblock_pfn_to_page(block_start_pfn,
 					     block_end_pfn, zone))
 			return;
+		cond_resched();
 	}
 
 	/* We confirm that there is no hole */
@@ -2400,6 +2401,14 @@ static inline void boost_watermark(struct zone *zone)
 
 	if (!watermark_boost_factor)
 		return;
+	/*
+	 * Don't bother in zones that are unlikely to produce results.
+	 * On small machines, including kdump capture kernels running
+	 * in a small area, boosting the watermark can cause an out of
+	 * memory situation immediately.
+	 */
+	if ((pageblock_nr_pages * 4) > zone_managed_pages(zone))
+		return;
 
 	max_boost = mult_frac(zone->_watermark[WMARK_HIGH],
 			watermark_boost_factor, 10000);

mm/percpu.c

@@ -80,6 +80,7 @@
 #include <linux/workqueue.h>
 #include <linux/kmemleak.h>
 #include <linux/sched.h>
+#include <linux/sched/mm.h>
 
 #include <asm/cacheflush.h>
 #include <asm/sections.h>
@@ -1557,10 +1558,9 @@ static struct pcpu_chunk *pcpu_chunk_addr_search(void *addr)
 static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved,
 				 gfp_t gfp)
 {
-	/* whitelisted flags that can be passed to the backing allocators */
-	gfp_t pcpu_gfp = gfp & (GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN);
-	bool is_atomic = (gfp & GFP_KERNEL) != GFP_KERNEL;
-	bool do_warn = !(gfp & __GFP_NOWARN);
+	gfp_t pcpu_gfp;
+	bool is_atomic;
+	bool do_warn;
 	static int warn_limit = 10;
 	struct pcpu_chunk *chunk, *next;
 	const char *err;
@@ -1569,6 +1569,12 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved,
 	void __percpu *ptr;
 	size_t bits, bit_align;
 
+	gfp = current_gfp_context(gfp);
+	/* whitelisted flags that can be passed to the backing allocators */
+	pcpu_gfp = gfp & (GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN);
+	is_atomic = (gfp & GFP_KERNEL) != GFP_KERNEL;
+	do_warn = !(gfp & __GFP_NOWARN);
+
 	/*
 	 * There is now a minimum allocation size of PCPU_MIN_ALLOC_SIZE,
 	 * therefore alignment must be a minimum of that many bytes.

mm/slub.c

@@ -551,15 +551,32 @@ static void print_section(char *level, char *text, u8 *addr,
 	metadata_access_disable();
 }
 
+/*
+ * See comment in calculate_sizes().
+ */
+static inline bool freeptr_outside_object(struct kmem_cache *s)
+{
+	return s->offset >= s->inuse;
+}
+
+/*
+ * Return offset of the end of info block which is inuse + free pointer if
+ * not overlapping with object.
+ */
+static inline unsigned int get_info_end(struct kmem_cache *s)
+{
+	if (freeptr_outside_object(s))
+		return s->inuse + sizeof(void *);
+	else
+		return s->inuse;
+}
+
 static struct track *get_track(struct kmem_cache *s, void *object,
 	enum track_item alloc)
 {
 	struct track *p;
 
-	if (s->offset)
-		p = object + s->offset + sizeof(void *);
-	else
-		p = object + s->inuse;
+	p = object + get_info_end(s);
 
 	return p + alloc;
 }
@@ -686,10 +703,7 @@ static void print_trailer(struct kmem_cache *s, struct page *page, u8 *p)
 		print_section(KERN_ERR, "Redzone ", p + s->object_size,
 			s->inuse - s->object_size);
 
-	if (s->offset)
-		off = s->offset + sizeof(void *);
-	else
-		off = s->inuse;
+	off = get_info_end(s);
 
 	if (s->flags & SLAB_STORE_USER)
 		off += 2 * sizeof(struct track);
@@ -782,7 +796,7 @@ static int check_bytes_and_report(struct kmem_cache *s, struct page *page,
  * object address
  * 	Bytes of the object to be managed.
  * 	If the freepointer may overlay the object then the free
- * 	pointer is the first word of the object.
+ *	pointer is at the middle of the object.
  *
  * 	Poisoning uses 0x6b (POISON_FREE) and the last byte is
  * 	0xa5 (POISON_END)
@@ -816,11 +830,7 @@ static int check_bytes_and_report(struct kmem_cache *s, struct page *page,
 
 static int check_pad_bytes(struct kmem_cache *s, struct page *page, u8 *p)
 {
-	unsigned long off = s->inuse;	/* The end of info */
-
-	if (s->offset)
-		/* Freepointer is placed after the object. */
-		off += sizeof(void *);
+	unsigned long off = get_info_end(s);	/* The end of info */
 
 	if (s->flags & SLAB_STORE_USER)
 		/* We also have user information there */
@@ -907,7 +917,7 @@ static int check_object(struct kmem_cache *s, struct page *page,
 		check_pad_bytes(s, page, p);
 	}
 
-	if (!s->offset && val == SLUB_RED_ACTIVE)
+	if (!freeptr_outside_object(s) && val == SLUB_RED_ACTIVE)
 		/*
 		 * Object and freepointer overlap. Cannot check
 		 * freepointer while object is allocated.
@@ -3587,6 +3597,11 @@ static int calculate_sizes(struct kmem_cache *s, int forced_order)
 		 *
 		 * This is the case if we do RCU, have a constructor or
 		 * destructor or are poisoning the objects.
+		 *
+		 * The assumption that s->offset >= s->inuse means free
+		 * pointer is outside of the object is used in the
+		 * freeptr_outside_object() function. If that is no
+		 * longer true, the function needs to be modified.
 		 */
 		s->offset = size;
 		size += sizeof(void *);

mm/vmscan.c

@@ -1625,7 +1625,6 @@ static __always_inline void update_lru_sizes(struct lruvec *lruvec,
  * @dst:	The temp list to put pages on to.
  * @nr_scanned:	The number of pages that were scanned.
  * @sc:		The scan_control struct for this reclaim session
- * @mode:	One of the LRU isolation modes
  * @lru:	LRU list id for isolating
  *
  * returns how many pages were moved onto *@dst.

scripts/decodecode

@@ -126,7 +126,7 @@ faultlinenum=$(( $(wc -l $T.oo  | cut -d" " -f1) - \
 faultline=`cat $T.dis | head -1 | cut -d":" -f2-`
 faultline=`echo "$faultline" | sed -e 's/\[/\\\[/g; s/\]/\\\]/g'`
 
-cat $T.oo | sed -e "${faultlinenum}s/^\(.*:\)\(.*\)/\1\*\2\t\t<-- trapping instruction/"
+cat $T.oo | sed -e "${faultlinenum}s/^\([^:]*:\)\(.*\)/\1\*\2\t\t<-- trapping instruction/"
 echo
 cat $T.aa
 cleanup

scripts/gdb/linux/rbtree.py

@@ -12,7 +12,7 @@ rb_node_type = utils.CachedType("struct rb_node")
 
 def rb_first(root):
     if root.type == rb_root_type.get_type():
-        node = node.address.cast(rb_root_type.get_type().pointer())
+        node = root.address.cast(rb_root_type.get_type().pointer())
     elif root.type != rb_root_type.get_type().pointer():
         raise gdb.GdbError("Must be struct rb_root not {}".format(root.type))
 
@@ -28,7 +28,7 @@ def rb_first(root):
 
 def rb_last(root):
     if root.type == rb_root_type.get_type():
-        node = node.address.cast(rb_root_type.get_type().pointer())
+        node = root.address.cast(rb_root_type.get_type().pointer())
     elif root.type != rb_root_type.get_type().pointer():
         raise gdb.GdbError("Must be struct rb_root not {}".format(root.type))
 

tools/testing/selftests/filesystems/epoll/epoll_wakeup_test.c

@@ -3,6 +3,7 @@
 #define _GNU_SOURCE
 #include <poll.h>
 #include <unistd.h>
+#include <assert.h>
 #include <signal.h>
 #include <pthread.h>
 #include <sys/epoll.h>
@@ -3136,4 +3137,149 @@ TEST(epoll59)
 	close(ctx.sfd[0]);
 }
 
+enum {
+	EPOLL60_EVENTS_NR = 10,
+};
+
+struct epoll60_ctx {
+	volatile int stopped;
+	int ready;
+	int waiters;
+	int epfd;
+	int evfd[EPOLL60_EVENTS_NR];
+};
+
+static void *epoll60_wait_thread(void *ctx_)
+{
+	struct epoll60_ctx *ctx = ctx_;
+	struct epoll_event e;
+	sigset_t sigmask;
+	uint64_t v;
+	int ret;
+
+	/* Block SIGUSR1 */
+	sigemptyset(&sigmask);
+	sigaddset(&sigmask, SIGUSR1);
+	sigprocmask(SIG_SETMASK, &sigmask, NULL);
+
+	/* Prepare empty mask for epoll_pwait() */
+	sigemptyset(&sigmask);
+
+	while (!ctx->stopped) {
+		/* Mark we are ready */
+		__atomic_fetch_add(&ctx->ready, 1, __ATOMIC_ACQUIRE);
+
+		/* Start when all are ready */
+		while (__atomic_load_n(&ctx->ready, __ATOMIC_ACQUIRE) &&
+		       !ctx->stopped);
+
+		/* Account this waiter */
+		__atomic_fetch_add(&ctx->waiters, 1, __ATOMIC_ACQUIRE);
+
+		ret = epoll_pwait(ctx->epfd, &e, 1, 2000, &sigmask);
+		if (ret != 1) {
+			/* We expect only signal delivery on stop */
+			assert(ret < 0 && errno == EINTR && "Lost wakeup!\n");
+			assert(ctx->stopped);
+			break;
+		}
+
+		ret = read(e.data.fd, &v, sizeof(v));
+		/* Since we are on ET mode, thus each thread gets its own fd. */
+		assert(ret == sizeof(v));
+
+		__atomic_fetch_sub(&ctx->waiters, 1, __ATOMIC_RELEASE);
+	}
+
+	return NULL;
+}
+
+static inline unsigned long long msecs(void)
+{
+	struct timespec ts;
+	unsigned long long msecs;
+
+	clock_gettime(CLOCK_REALTIME, &ts);
+	msecs = ts.tv_sec * 1000ull;
+	msecs += ts.tv_nsec / 1000000ull;
+
+	return msecs;
+}
+
+static inline int count_waiters(struct epoll60_ctx *ctx)
+{
+	return __atomic_load_n(&ctx->waiters, __ATOMIC_ACQUIRE);
+}
+
+TEST(epoll60)
+{
+	struct epoll60_ctx ctx = { 0 };
+	pthread_t waiters[ARRAY_SIZE(ctx.evfd)];
+	struct epoll_event e;
+	int i, n, ret;
+
+	signal(SIGUSR1, signal_handler);
+
+	ctx.epfd = epoll_create1(0);
+	ASSERT_GE(ctx.epfd, 0);
+
+	/* Create event fds */
+	for (i = 0; i < ARRAY_SIZE(ctx.evfd); i++) {
+		ctx.evfd[i] = eventfd(0, EFD_NONBLOCK);
+		ASSERT_GE(ctx.evfd[i], 0);
+
+		e.events = EPOLLIN | EPOLLET;
+		e.data.fd = ctx.evfd[i];
+		ASSERT_EQ(epoll_ctl(ctx.epfd, EPOLL_CTL_ADD, ctx.evfd[i], &e), 0);
+	}
+
+	/* Create waiter threads */
+	for (i = 0; i < ARRAY_SIZE(waiters); i++)
+		ASSERT_EQ(pthread_create(&waiters[i], NULL,
+					 epoll60_wait_thread, &ctx), 0);
+
+	for (i = 0; i < 300; i++) {
+		uint64_t v = 1, ms;
+
+		/* Wait for all to be ready */
+		while (__atomic_load_n(&ctx.ready, __ATOMIC_ACQUIRE) !=
+		       ARRAY_SIZE(ctx.evfd))
+			;
+
+		/* Steady, go */
+		__atomic_fetch_sub(&ctx.ready, ARRAY_SIZE(ctx.evfd),
+				   __ATOMIC_ACQUIRE);
+
+		/* Wait all have gone to kernel */
+		while (count_waiters(&ctx) != ARRAY_SIZE(ctx.evfd))
+			;
+
+		/* 1ms should be enough to schedule away */
+		usleep(1000);
+
+		/* Quickly signal all handles at once */
+		for (n = 0; n < ARRAY_SIZE(ctx.evfd); n++) {
+			ret = write(ctx.evfd[n], &v, sizeof(v));
+			ASSERT_EQ(ret, sizeof(v));
+		}
+
+		/* Busy loop for 1s and wait for all waiters to wake up */
+		ms = msecs();
+		while (count_waiters(&ctx) && msecs() < ms + 1000)
+			;
+
+		ASSERT_EQ(count_waiters(&ctx), 0);
+	}
+	ctx.stopped = 1;
+	/* Stop waiters */
+	for (i = 0; i < ARRAY_SIZE(waiters); i++)
+		ret = pthread_kill(waiters[i], SIGUSR1);
+	for (i = 0; i < ARRAY_SIZE(waiters); i++)
+		pthread_join(waiters[i], NULL);
+
+	for (i = 0; i < ARRAY_SIZE(waiters); i++)
+		close(ctx.evfd[i]);
+	close(ctx.epfd);
+}
+
 TEST_HARNESS_MAIN

tools/testing/selftests/wireguard/qemu/debug.config

@@ -25,7 +25,6 @@ CONFIG_KASAN=y
 CONFIG_KASAN_INLINE=y
 CONFIG_UBSAN=y
 CONFIG_UBSAN_SANITIZE_ALL=y
-CONFIG_UBSAN_NO_ALIGNMENT=y
 CONFIG_UBSAN_NULL=y
 CONFIG_DEBUG_KMEMLEAK=y
 CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE=8192