Re: [PATCH 1/1] RDMA/iwcm: Fix WARNING:at_kernel/workqueue.c:#check_flush_dependency

[Bart Van Assche <bvanassche@acm.org>]

On 8/17/24 1:42 AM, Zhu Yanjun wrote:
> When workqueue_flush is invoked, WQ_MEM_RECLAIM is checked to avoid
> errors.

This description is too brief and not entirely correct. In the
description of this patch it should be explained that WQ_MEM_RECLAIM 
must be set for workqueues that are flushed from a work item queued on
a WQ_MEM_RECLAIM workqueue or from a memory reclaim context. Otherwise a
deadlock can occur. From kernel/workqueue.c:

/**
  * check_flush_dependency - check for flush dependency sanity
  * @target_wq: workqueue being flushed
  * @target_work: work item being flushed (NULL for workqueue flushes)
  *
  * %current is trying to flush the whole @target_wq or @target_work on it.
  * If @target_wq doesn't have %WQ_MEM_RECLAIM, verify that %current is not
  * reclaiming memory or running on a workqueue which doesn't have
  * %WQ_MEM_RECLAIM as that can break forward-progress guarantee leading to
  * a deadlock.
  */

> Reported-by: kernel test robot <oliver.sang@intel.com>
> Closes: https://lore.kernel.org/oe-lkp/202408151633.fc01893c-oliver.sang@intel.com
> Signed-off-by: Zhu Yanjun <yanjun.zhu@linux.dev>

Since this is a fix, please include a "Fixes:" tag.

Thanks,

Bart.