This could happen when a process disappeared while we were reading its
file descriptor list.
I was able to replicate the problem by running this in another
terminal:
while :; do for i in $(seq 10); do
/bin/true & done >&/dev/null; wait >&/dev/null;
done
And then running the portlist tests thousands of times.
Fixes#339.
Signed-off-by: Avery Pennarun <apenwarr@tailscale.com>
I noticed portlist when looking at some profiles and hadn't looked at
the code much before. This is a first pass over it. It allocates a
fair bit. More love remains, but this does a bit:
name old time/op new time/op delta
GetList-8 9.92ms ± 8% 9.64ms ±12% ~ (p=0.247 n=10+10)
name old alloc/op new alloc/op delta
GetList-8 931kB ± 0% 869kB ± 0% -6.70% (p=0.000 n=10+10)
name old allocs/op new allocs/op delta
GetList-8 4.59k ± 0% 3.69k ± 1% -19.71% (p=0.000 n=10+10)
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
