We've run into an issue (on 2.6.10) where calling "lsof" triggers lost
packets on our server. Preempt is disabled, and NAPI is enabled.
It appears that for some reason the networking softirq is not being
handled in a timely fashion, which means that the rx ring buffer fills
up and packets overflow.
It appears that the problem path is:
seq_read
tcp_seq_next
established_get_next
read_lock/read_unlock
The issue appears to be related to the amount of time that this syscall
takes. While we're in the syscall we cannot run the softirqd thread,
and so the rx buffer is not being cleaned.
The fact that there are kmalloc(GFP_KERNEL) calls in seq_read() seems to
indicate that sleeping is safe, so would it be reasonable to call
schedule() periodically (maybe based on elapsed time) to ensure that
system latency is kept under control?
Thanks,
Chris
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