On Tue, Jan 04, 2022 at 03:51:48PM -0800, Hridya Valsaraju wrote:
Recently, we noticed an issue where a process went into direct reclaim while holding the kernfs rw semaphore for sysfs in write(exclusive) mode. This caused processes who were doing DMA-BUF exports and releases to go into uninterruptible sleep since they needed to acquire the same semaphore for the DMA-BUF sysfs entry creation/deletion. In order to avoid blocking DMA-BUF export/release for an indeterminate amount of time while another process is holding the sysfs rw semaphore in exclusive mode, this patch moves the per-buffer sysfs file creation/deleteion to a kthread.
Fixes: bdb8d06dfefd ("dmabuf: Add the capability to expose DMA-BUF stats in sysfs") Signed-off-by: Hridya Valsaraju hridya@google.com
drivers/dma-buf/dma-buf-sysfs-stats.c | 343 ++++++++++++++++++++++++-- include/linux/dma-buf.h | 46 ++++ 2 files changed, 366 insertions(+), 23 deletions(-)
Crazy, but if this works in your testing, it looks ok to me. Nice work.
Reviewed-by: Greg Kroah-Hartman gregkh@linuxfoundation.org