Messages in this thread | | | Date | Sat, 29 Mar 2008 09:16:02 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [PATCH 1/2] do_wait reorganization |
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On Fri, 28 Mar 2008, Roland McGrath wrote: > > The control flow is less nonobvious without so much goto.
How about a further non-obviousness?
> +static int wait_consider_task(struct task_struct *parent, > + struct task_struct *p, int *retval, > + enum pid_type type, struct pid *pid, int options, > + struct siginfo __user *infop, > + int __user *stat_addr, struct rusage __user *ru) > +{ ... > + if (task_is_stopped_or_traced(p)) { > + /* > + * It's stopped now, so it might later > + * continue, exit, or stop again. > + */ > + *retval = 0; > + if ((p->ptrace & PT_PTRACED) || > + (options & WUNTRACED)) { > + *retval = wait_task_stopped(p, (options & WNOWAIT), > + infop, stat_addr, ru); > + if (*retval) > + return 1; > + } > + } else if (p->exit_state == EXIT_ZOMBIE && !delay_group_leader(p)) { ... > + return 0;
I think it would be even more obvious (or, to use your phrase, "less nonobvious") if this was written like so:
if (task_is_stopped_or_traced(p)) { ... .... if (*retval} return 1; } return 0; }
if (p->exit_state == EXIT_ZOMBIE && !delay_group_leader(p)) { ... return 0; }
if (...)
because then you can clearly see that smething like the "task_is_stopped_or_traced(p)" case is complete in itself, and only has its own local stuff going on.
(And at some point I'd also almost make each case a trivial small inline function of its on, but in this case there are so many arguments to pass around that it probably becomes _less_ readable that way).
I also wonder if you really need both "int *retval" and the return value. Isn't "retval" always going to be zero or a negative errno? And the return value is going to be either true of false? Why not just fold them into one single thing:
- negative: all done, with error - zero: this didn't trigger, continue with the next one in caller - positive: this thread triggered, all done, return 0 in the caller.
which is (I think) close to what we already do in eligible_child() (so this would not be a new calling convention for this particular code).
Linus
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