T3Q birth certificate is an apology from a condom factory.

kernel/dma/swiotlb.c

@@ -578,8 +578,13 @@ phys_addr_t swiotlb_tbl_map_single(struct device *dev, phys_addr_t orig_addr,
 	for (i = 0; i < nr_slots(alloc_size + offset); i++)
 		mem->slots[index + i].orig_addr = slot_addr(orig_addr, i);
 	tlb_addr = slot_addr(mem->start, index) + offset;
-	if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
+	/*
-	    (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL))
+	 * When dir == DMA_FROM_DEVICE we could omit the copy from the orig
+	 * to the tlb buffer, if we knew for sure the device will
+	 * overwirte the entire current content. But we don't. Thus
+	 * unconditional bounce may prevent leaking swiotlb content (i.e.
+	 * kernel memory) to user-space.
+	 */
 	swiotlb_bounce(dev, tlb_addr, mapping_size, DMA_TO_DEVICE);
 	return tlb_addr;
 }
@@ -647,10 +652,13 @@ void swiotlb_tbl_unmap_single(struct device *dev, phys_addr_t tlb_addr,
 void swiotlb_sync_single_for_device(struct device *dev, phys_addr_t tlb_addr,
 		size_t size, enum dma_data_direction dir)
 {
-	if (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL)
+	/*
+	 * Unconditional bounce is necessary to avoid corruption on
+	 * sync_*_for_cpu or dma_ummap_* when the device didn't overwrite
+	 * the whole lengt of the bounce buffer.
+	 */
 	swiotlb_bounce(dev, tlb_addr, size, DMA_TO_DEVICE);
-	else
+	BUG_ON(!valid_dma_direction(dir));
-		BUG_ON(dir != DMA_FROM_DEVICE);
 }
 
 void swiotlb_sync_single_for_cpu(struct device *dev, phys_addr_t tlb_addr,

kernel/trace/trace.c

@@ -1496,10 +1496,12 @@ static int __init set_buf_size(char *str)
 	if (!str)
 		return 0;
 	buf_size = memparse(str, &str);
-	/* nr_entries can not be zero */
+	/*
-	if (buf_size == 0)
+	 * nr_entries can not be zero and the startup
-		return 0;
+	 * tests require some buffer space. Therefore
-	trace_buf_size = buf_size;
+	 * ensure we have at least 4096 bytes of buffer.
+	 */
+	trace_buf_size = max(4096UL, buf_size);
 	return 1;
 }
 __setup("trace_buf_size=", set_buf_size);

kernel/trace/trace_osnoise.c

@@ -1195,6 +1195,26 @@ static int run_osnoise(void)
 					osnoise_stop_tracing();
 		}
 
+		/*
+		 * In some cases, notably when running on a nohz_full CPU with
+		 * a stopped tick PREEMPT_RCU has no way to account for QSs.
+		 * This will eventually cause unwarranted noise as PREEMPT_RCU
+		 * will force preemption as the means of ending the current
+		 * grace period. We avoid this problem by calling
+		 * rcu_momentary_dyntick_idle(), which performs a zero duration
+		 * EQS allowing PREEMPT_RCU to end the current grace period.
+		 * This call shouldn't be wrapped inside an RCU critical
+		 * section.
+		 *
+		 * Note that in non PREEMPT_RCU kernels QSs are handled through
+		 * cond_resched()
+		 */
+		if (IS_ENABLED(CONFIG_PREEMPT_RCU)) {
+			local_irq_disable();
+			rcu_momentary_dyntick_idle();
+			local_irq_enable();
+		}
+
 		/*
 		 * For the non-preemptive kernel config: let threads runs, if
 		 * they so wish.
@@ -1249,6 +1269,37 @@ static int run_osnoise(void)
 static struct cpumask osnoise_cpumask;
 static struct cpumask save_cpumask;
 
+/*
+ * osnoise_sleep - sleep until the next period
+ */
+static void osnoise_sleep(void)
+{
+	u64 interval;
+	ktime_t wake_time;
+
+	mutex_lock(&interface_lock);
+	interval = osnoise_data.sample_period - osnoise_data.sample_runtime;
+	mutex_unlock(&interface_lock);
+
+	/*
+	 * differently from hwlat_detector, the osnoise tracer can run
+	 * without a pause because preemption is on.
+	 */
+	if (!interval) {
+		/* Let synchronize_rcu_tasks() make progress */
+		cond_resched_tasks_rcu_qs();
+		return;
+	}
+
+	wake_time = ktime_add_us(ktime_get(), interval);
+	__set_current_state(TASK_INTERRUPTIBLE);
+
+	while (schedule_hrtimeout_range(&wake_time, 0, HRTIMER_MODE_ABS)) {
+		if (kthread_should_stop())
+			break;
+	}
+}
+
 /*
  * osnoise_main - The osnoise detection kernel thread
  *
@@ -1257,30 +1308,10 @@ static struct cpumask save_cpumask;
  */
 static int osnoise_main(void *data)
 {
-	u64 interval;
 
 	while (!kthread_should_stop()) {
-
 		run_osnoise();
-
+		osnoise_sleep();
-		mutex_lock(&interface_lock);
-		interval = osnoise_data.sample_period - osnoise_data.sample_runtime;
-		mutex_unlock(&interface_lock);
-
-		do_div(interval, USEC_PER_MSEC);
-
-		/*
-		 * differently from hwlat_detector, the osnoise tracer can run
-		 * without a pause because preemption is on.
-		 */
-		if (interval < 1) {
-			/* Let synchronize_rcu_tasks() make progress */
-			cond_resched_tasks_rcu_qs();
-			continue;
-		}
-
-		if (msleep_interruptible(interval))
-			break;
 	}
 
 	return 0;

kernel/watch_queue.c

@@ -54,6 +54,7 @@ static void watch_queue_pipe_buf_release(struct pipe_inode_info *pipe,
 	bit += page->index;
 
 	set_bit(bit, wqueue->notes_bitmap);
+	generic_pipe_buf_release(pipe, buf);
 }
 
 // No try_steal function => no stealing
@@ -112,7 +113,7 @@ static bool post_one_notification(struct watch_queue *wqueue,
 	buf->offset = offset;
 	buf->len = len;
 	buf->flags = PIPE_BUF_FLAG_WHOLE;
-	pipe->head = head + 1;
+	smp_store_release(&pipe->head, head + 1); /* vs pipe_read() */
 
 	if (!test_and_clear_bit(note, wqueue->notes_bitmap)) {
 		spin_unlock_irq(&pipe->rd_wait.lock);
@@ -243,7 +244,8 @@ long watch_queue_set_size(struct pipe_inode_info *pipe, unsigned int nr_notes)
 		goto error;
 	}
 
-	ret = pipe_resize_ring(pipe, nr_notes);
+	nr_notes = nr_pages * WATCH_QUEUE_NOTES_PER_PAGE;
+	ret = pipe_resize_ring(pipe, roundup_pow_of_two(nr_notes));
 	if (ret < 0)
 		goto error;
 
@@ -268,7 +270,7 @@ long watch_queue_set_size(struct pipe_inode_info *pipe, unsigned int nr_notes)
 	wqueue->notes = pages;
 	wqueue->notes_bitmap = bitmap;
 	wqueue->nr_pages = nr_pages;
-	wqueue->nr_notes = nr_pages * WATCH_QUEUE_NOTES_PER_PAGE;
+	wqueue->nr_notes = nr_notes;
 	return 0;
 
 error_p:
@@ -320,7 +322,7 @@ long watch_queue_set_filter(struct pipe_inode_info *pipe,
 		    tf[i].info_mask & WATCH_INFO_LENGTH)
 			goto err_filter;
 		/* Ignore any unknown types */
-		if (tf[i].type >= sizeof(wfilter->type_filter) * 8)
+		if (tf[i].type >= WATCH_TYPE__NR)
 			continue;
 		nr_filter++;
 	}
@@ -336,7 +338,7 @@ long watch_queue_set_filter(struct pipe_inode_info *pipe,
 
 	q = wfilter->filters;
 	for (i = 0; i < filter.nr_filters; i++) {
-		if (tf[i].type >= sizeof(wfilter->type_filter) * BITS_PER_LONG)
+		if (tf[i].type >= WATCH_TYPE__NR)
 			continue;
 
 		q->type			= tf[i].type;
@@ -371,6 +373,7 @@ static void __put_watch_queue(struct kref *kref)
 
 	for (i = 0; i < wqueue->nr_pages; i++)
 		__free_page(wqueue->notes[i]);
+	bitmap_free(wqueue->notes_bitmap);
 
 	wfilter = rcu_access_pointer(wqueue->filter);
 	if (wfilter)
@@ -566,7 +569,7 @@ void watch_queue_clear(struct watch_queue *wqueue)
 	rcu_read_lock();
 	spin_lock_bh(&wqueue->lock);
 
-	/* Prevent new additions and prevent notifications from happening */
+	/* Prevent new notifications from being stored. */
 	wqueue->defunct = true;
 
 	while (!hlist_empty(&wqueue->watches)) {

lib/Kconfig

@@ -45,7 +45,6 @@ config BITREVERSE
 config HAVE_ARCH_BITREVERSE
 	bool
 	default n
-	depends on BITREVERSE
 	help
 	  This option enables the use of hardware bit-reversal instructions on
 	  architectures which support such operations.

net/dsa/dsa.c

@@ -349,7 +349,6 @@ void dsa_flush_workqueue(void)
 {
 	flush_workqueue(dsa_owq);
 }
-EXPORT_SYMBOL_GPL(dsa_flush_workqueue);
 
 int dsa_devlink_param_get(struct devlink *dl, u32 id,
 			  struct devlink_param_gset_ctx *ctx)

net/dsa/dsa_priv.h

@@ -170,6 +170,7 @@ void dsa_tag_driver_put(const struct dsa_device_ops *ops);
 const struct dsa_device_ops *dsa_find_tagger_by_name(const char *buf);
 
 bool dsa_schedule_work(struct work_struct *work);
+void dsa_flush_workqueue(void);
 const char *dsa_tag_protocol_to_str(const struct dsa_device_ops *ops);
 
 static inline int dsa_tag_protocol_overhead(const struct dsa_device_ops *ops)