[Qemu-devel] gdbstub chews cpu due to nonblocking socket mode

[Mike Frysinger]

i'm not sure if someone has brought this up before (i cant find
anything in the archives), but using the gdbstub with qemu seems to
cause quite a bit of useless cpu chewing.

in gdbstub.c:gdb_accept(), after the connection has been established, we see:
    fcntl(fd, F_SETFL, O_NONBLOCK);

then, when the gdb connection is idle (the process is stopped, and gdb
is waiting for input from the user), the main polling loop in
gdb_handlesig() will call read() over and over again as fast as
possible and thus eat a cpu.

is there any need for this to be nonblocking ?  ive commented out that
one line and have yet to notice a problem during my development (using
singlestep, breakpoints, continue, etc...).
-mike