Re: [9fans] libthread help ...

["Russ Cox" <rsc@plan9.bell-labs.com>]

if you run acid -l thread, it loads some
useful functions.  one such function is
"stacks()", which prints the stack for all
the threads in all the procs of the program.

if you run this on your program, you see
(i've deleted all but the relevant lines):

acid: stacks()
------
	threadmain:
	0x00022328	1		Rendezvous 		alt(tag(*148068=0) 0: send(channel(223368)))

sendul(c=0x00036888,v=0x00000002) /sys/src/libthread/channel.c:231
	called from threadmain+0x254 /tmp/a.c:106
------
	mouseproc:
	0x000366c8	2		Rendezvous 		alt(tag(*240176=0) 0: send(channel(222792)))

send(c=0x00036648,v=0x0003aab4) /sys/src/libthread/channel.c:209
	called from _ioproc+0x149 /sys/src/libdraw/mouse.c:85
------
	0x00036788	3		Rendezvous 		alt(tag(*244856=0) 0: send(channel(223048)))

sendul(c=0x00036748,v=0x00000001) /sys/src/libthread/channel.c:231
	called from clockproc+0x63 /tmp/a.c:25
------
	0x000368c8	4		Rendezvous 		alt(tag(*249380=0) 0: send(channel(223304)))

sendul(c=0x00036848,v=0x00000000) /sys/src/libthread/channel.c:231
	called from menuhitproc+0xad /tmp/a.c:57
------

the problem is that the menuhitproc and main are
both reading from the mouse.  main got a new mouse
event to send to menuhitproc, and menuhitproc is
trying to send its result to main at the same time.
perhaps you should wait for the menuhitproc to
send its result before waiting for more mouse ops.

you could change a[0].op to CHANNOP after sending
to menuhitproc and then change it back after getting
the result.

i don't see why it's a separate proc.  you might want
main not to stop processing clock ticks while you
wait for the menu event, i guess, but even then you
could do that with a thread rather than a proc.

russ