Commit bb9025f4 authored May 04, 2024 by Fedor Pchelkin Committed by Christoph Hellwig May 23, 2024

dma-mapping: benchmark: fix up kthread-related error handling



kthread creation failure is invalidly handled inside do_map_benchmark().
The put_task_struct() calls on the error path are supposed to balance the
get_task_struct() calls which only happen after all the kthreads are
successfully created. Rollback using kthread_stop() for already created
kthreads in case of such failure.

In normal situation call kthread_stop_put() to gracefully stop kthreads
and put their task refcounts. This should be done for all started
kthreads.

Found by Linux Verification Center (linuxtesting.org).

Fixes: 65789daa ("dma-mapping: add benchmark support for streaming DMA APIs")
Suggested-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

parent c760b372

kernel/dma/map_benchmark.c

+10 −6

Original line number	Diff line number	Diff line
		@@ -118,6 +118,8 @@ static int do_map_benchmark(struct map_benchmark_data *map)
		if (IS_ERR(tsk[i])) {
		pr_err("create dma_map thread failed\n");
		ret = PTR_ERR(tsk[i]);
		while (--i >= 0)
		kthread_stop(tsk[i]);
		goto out;
		}

		@@ -139,12 +141,16 @@ static int do_map_benchmark(struct map_benchmark_data *map)

		msleep_interruptible(map->bparam.seconds * 1000);

		/* wait for the completion of benchmark threads */
		/* wait for the completion of all started benchmark threads */
		for (i = 0; i < threads; i++) {
		ret = kthread_stop(tsk[i]);
		int kthread_ret = kthread_stop_put(tsk[i]);

		if (kthread_ret)
		ret = kthread_ret;
		}

		if (ret)
		goto out;
		}

		loops = atomic64_read(&map->loops);
		if (likely(loops > 0)) {
		@@ -170,8 +176,6 @@ static int do_map_benchmark(struct map_benchmark_data *map)
		}

		out:
		for (i = 0; i < threads; i++)
		put_task_struct(tsk[i]);
		put_device(map->dev);
		kfree(tsk);
		return ret;