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apache / nuttx

Apache NuttX is a mature, real-time embedded operating system (RTOS)
https://nuttx.apache.org/
Apache License 2.0
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CONFIG_NET_TCP_WRITE_BUFFERS=y lead to deadlock #5973

Open pkarashchenko opened 2 years ago

pkarashchenko commented 2 years ago

Recently I've been testing FTPD operation on custom SAME70 based board with FileZilla FTP client. I had CONFIG_NET_TCP_WRITE_BUFFERS=y.

I have a folder with 2 files that I try to upload from laptop to device. Upload of a folder fails.

FileZilla starts 2 FTP sessions in parallel one for each file upload so 2 instances of ftpd_worker are started. The situation happens in 80% of my tests. The FTP client send "STOR" command for both files and by adding extra logs I see that both threads reach ftpd.c:1908 code ret = ftpd_response(session->cmd.sd, session->txtimeout, g_respfmt1, 150, ' ', "Opening data connection"); at the same time so send is called concurrently.

The logs before ftpd_response call are printed, but there are no logs after ftpd_response call. NSH "ps" shows that both threads are "waiting for semaphore", but most probably loop somewhere inside the psock_tcp_send trying to allocate iob.

Setting CONFIG_NET_TCP_WRITE_BUFFERS=n solves the issue and FTP server operates as expected.

fjpanag commented 1 year ago

I am hitting the exact same issue with a custom server, on high load.

TCP deadlocks during send when it tries to allocate an iob.

anchao commented 1 year ago

Does this issue still exist on the latest nuttx? recently I fixed a similar issue, I don’t know if there is any improvement for ftpd

https://github.com/apache/nuttx/pull/8130