Re: [PATCH] erofs: Wake up all waiters after z_erofs_lzma_head ready.

From: Gao Xiang
Date: Sat Jun 25 2022 - 05:44:59 EST


Hi,

On Sat, Jun 25, 2022 at 04:57:38PM +0800, Even wrote:
> From: Even <chenyuwen1@xxxxxxxxx>
>
> When the user mounts the erofs second times, the decompression thread
> may hung. The problem happens due to a sequence of steps like the
> following:
>
> 1) Task A called z_erofs_load_lzma_config which obtain all of the node
> from the z_erofs_lzma_head.
>
> 2) At this time, task B called the z_erofs_lzma_decompress and wanted to
> get a node. But the z_erofs_lzma_head was empty, the Task B had to
> sleep.
>
> 3) Task A release nodes and push nodes into the z_erofs_lzma_head. But
> task B was still sleeping.
>
> One example report when the hung happens:
> task:kworker/u3:1 state:D stack:14384 pid: 86 ppid: 2 flags:0x00004000
> Workqueue: erofs_unzipd z_erofs_decompressqueue_work
> Call Trace:
> <TASK>
> __schedule+0x281/0x760
> schedule+0x49/0xb0
> z_erofs_lzma_decompress+0x4bc/0x580
> ? cpu_core_flags+0x10/0x10
> z_erofs_decompress_pcluster+0x49b/0xba0
> ? __update_load_avg_se+0x2b0/0x330
> ? __update_load_avg_se+0x2b0/0x330
> ? update_load_avg+0x5f/0x690
> ? update_load_avg+0x5f/0x690
> ? set_next_entity+0xbd/0x110
> ? _raw_spin_unlock+0xd/0x20
> z_erofs_decompress_queue.isra.0+0x2e/0x50
> z_erofs_decompressqueue_work+0x30/0x60
> process_one_work+0x1d3/0x3a0
> worker_thread+0x45/0x3a0
> ? process_one_work+0x3a0/0x3a0
> kthread+0xe2/0x110
> ? kthread_complete_and_exit+0x20/0x20
> ret_from_fork+0x22/0x30
> </TASK>
>
> Signed-off-by: Even <chenyuwen1@xxxxxxxxx>

Thanks a lot for catching this!

The patch itself looks good, but could you use your real name to sign
off the patch and resend a version? see,
https://www.kernel.org/doc/html/v4.17/process/submitting-patches.html#developer-s-certificate-of-origin-1-1

Otherwise it looks good to me,
Reviewed-by: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx>

Thanks,
Gao Xiang