Re: [9fans] threads in Plan 9

[Richard Miller <miller@hamnavoe.demon.co.uk>]

> I used to have great fun with mothra when one process would crash, and
> leave the rest deadlocked or otherwise boggled.

This behaviour seems to be a consequence of the atnotify handler
in the event(2) package used by mothra.

When a note is received in the main process, the handler sends a "die" note
to all the subprocesses and returns 0 to request the default exception
action (exit or suspend).  But when a note is received in a subprocess, the
handler simply returns 1 to request continuation.  If the note occurred
during a system call (e.g. reading from the network), in most cases the
continued mothra process will detect the abnormal return and exit.  If not,
the "die" note is simply ignored and deadlock results.

I wonder whether /sys/src/libdraw/event.c:#6972,#6980 should be "return 0" ?

-- Richard